Should You Get A 3 Phase Solar Inverter?

three phase solar inverter

There are a few things you need to know if you are getting a 3-phase solar inverter and expect to add a battery later.

I love three-phase solar inverters.

If your home has a three-phase supply and you do not want or need micro-inverters then my recommendation is to use a three-phase solar inverter over a single-phase model.

What the hell is a three-phase solar inverter?

A three-phase solar inverter  takes DC electricity from solar panels, chops it up and sends it out as AC electricity shared across a three-phase supply.

DC to 3-phase

DC in. Three-phase AC out.

They cost about $300 more than the equivalent single-phase solar inverter, but look the same:

three-phase solar inverter models

If it is a 3-phase Fronius it will say ‘Symo’ on it. If it is a 3-phase SMA it will be blue.


What the hell is a three-phase supply?

Most homes in Australia have a single-phase electricity supply. This means that they have one live wire coming in from the grid.

single-phase electricity supply

A single-phase supply


A three-phase home has 3 live wires coming in from the grid.

three-phase electricity supply

A three-phase supply

This means three-phase homes can pull more power from the grid.  Handy for particularly big loads such as a:

  • large air conditioner
  • pool heater
  • spa
  • sauna
  • electric car charger
  • etc.

And of course a three-phase supply means you can send much more solar energy back into the grid compared to single-phase (three to six times as much depending on your local DNSP rules).

How do you know if you have a three-phase supply?

Carefully (don’t touch anything!) look in your switchboard. Count the ‘poles’ on your main switch or meter isolator. If you have single-phase you’ll only have one. Three-phase homes will have 3 like this:

three-phase switchboard

The main switch on a three-phase switchboard.


three-phase meter isolator

The meter isolator on a three-phase switchboard.

What are your options if you have a three-phase supply and want solar power?

If you have three-phase supply you can have either:

  • A single-phase solar inverter
  • Microinverters
  • A three-phase solar inverter

Any of these choices are valid. It will not affect how you are billed for exports or how much solar energy is self consumed.

But, I still recommend a three-phase solar inverter.

Why do you recommend a three-phase inverter?

Spreading the inverter capacity across the three wires coming into your home means that you don’t have to push the solar energy as hard to get it out to the grid. You’ll be increasing the local grid voltage less than a single-phase install and you’ll have less throttling or tripping off due to over-voltage issues. That means more solar power production with our high-voltage plagued Australian grid.

Voltage rise related solar issues are one of the biggest problems we see with installed solar power systems. I go in to detail on the causes and solutions for voltage rise issues here.

So to reiterate for the blog post skimmers:

If you have a three-phase supply I recommend getting a three-phase solar inverter. Why? Because it drastically reduces the chance of having voltage rise issues.

But not everyone agrees with me on this.

There is one downside to using a three-phase inverter other than the extra cost (expect to pay $300 to $500 more compared to a single-phase inverter). Three-phase solar inverters do make it much more expensive to have ‘Apocalypse Proof Battery Backup™’.

What is Apocalypse Proof Battery Backup?

My definition of regular battery backup is this: when the grid goes down your battery system powers some specially selected ‘essential circuits’. If the battery gets drained during the blackout, your home will black out too. In this configuration, the solar panels cannot charge your battery without the grid.

My definition of Apocalypse Proof Battery Backup : when the grid goes down your battery system powers some specially selected ‘essential circuits’. But if the sun is shining the solar panels help power your home and recharge the battery too. If you are careful with your consumption, you can carry on indefinitely charging the batteries with the sun by day and using the battery at night.

Why a 3-phase solar inverter makes Apocalypse Proof Backup very expensive.

If you have a three-phase home with a single-phase solar inverter (or microinverters) then, with the right battery – such as a Powerwall 2 – Apocalypse Proof Backup is easy and can be done out of the box:

single-phase solar inverter and AC coupled battery

A single-phase solar inverter and an AC coupled battery. The backup is all on the ‘black’ phase.

When the grid goes down in this configuration the battery system isolates the house from the grid (islands) and keeps 230V on the ‘black’ phase so the solar inverter does not shut down. The solar panels continue to send power to the house and battery. The solar inverter is throttled using frequency shifting if there is ever more solar power than the house and battery can handle.

But if you add a battery to a system with a three-phase solar inverter it is more complicated. If the grid goes down you need to keep 230V on all three-phases to stop the solar inverter shutting down. A battery with a single-phase battery inverter (such as a Powerwall 2) cannot do this. You will be able to have ‘regular’ backup – but once the batteries are drained you’ll have no power until the grid comes back.

The solution to this is expensive. You either need a three-phase battery inverter – and if you know of one please let me know in the comments – I’ve never seen one for sale. It would look like this:

three-phase solar and battery inverter

three-phase battery inverter and three-phase solar inverter

Or you have 3 batteries and battery inverters – one on each phase. But again – I don’t know of any battery systems that can play nice with a separate three-phase solar inverter. The Powerwall 2 cannot work in this configuration. Yet.

Or of course you could swap your three-phase solar inverter out for a three-phase hybrid inverter and DC Couple your battery:

 three-phase hybrid inverter

A three-phase hybrid inverter.

But all these options are very expensive. So if you are choosing between a three-phase solar inverter and a single-phase solar inverter/microinverters the question you have to ask your self is:

What’s more important to you? Apocalypse Proof Backup™ or stable solar generation?

In my humble opinion it is better to have a system that operates well 99.9% of the time (when the grid is available) over one that operates really well 0.1% of the time (when the grid is down).

But perhaps your grid electricity goes down much more than that and getting through long outages is your priority. In that case you may want to install a single-phase solar inverter on your 3-phase supply.  Just make sure that your installer checks your local grid voltage and voltage rise before you get solar installed. And hope that your local grid voltage stays low in the future.

You could also install a three-phase hybrid inverter instead of a three-phase solar inverter. But bear in mind that any future battery must be compatible with that inverter – often that is only 2 or 3 battery models and they may be obsolete by the time you decide to buy them.

So choose wisely three-phase dweller. And do the right thing based on your local grid voltage, your local grid reliability and above-all your zombie tolerance.

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and the founder and CEO of I started SolarQuotes in 2009 and the SolarQuotes blog in 2013 with the belief that it’s more important to be truthful and objective than popular. My last "real job" was working for the CSIRO in their renewable energy division. Since 2009, I’ve helped over 700,000 Aussies get quotes for solar from installers I trust. Read my full bio.


  1. Tim Efthymiou says

    Good write up Finn. 100%, not doubt, you should get a three phase inverter (if you have three phase at your home or business). This way you could split your solar system in three and split the load on your phases evenly. For eg. don’t have your air cond., fridge, dryer on the same load, split them around with your lights and power to even out the demand as not to overload one phase. Cheers for now.

    • Michael Foley says

      Why not throw a charge controller in between panels and batteries. As an off grid system is set up. And or bump off solar or split power production to charge controller then batteries and also to inverter

    • Hi Finn,

      I’m building on a hobby farm lot where power interruption is rather frequent and prolong outages of up to a week can be a possibility like what happened during the recent bushfire as such apocalypse backup is my priority.

      The site has 3ph power but even though I’ve instructed my electrician to bring 3ph from the meter box to the house, all house requirements are currently only single phase.

      I’m thinking of the Delta E5 inverter possibly connected to the phase that have most of the power outlets, maybe leaving the other phases for the air-conditioning, cooking and hot water.

      Can I have your thoughts on this? Thanks!

      • Lawrence Coomber says


        Based on what you have described you should consider a 3 phase off grid solution rather than waste money in bringing 3 phase from the grid.

        You also have a little known advantage in that you have already a single phase grid connection, and this can be exploited well in a dual on-grid plus independent off grid design.

        Contact me if you want some detailed advice Norman.

        Lawrence Coomber

        • Hi Lawrence,

          The 3 phase Meter is already available at my meter box at the corner of the lot, so off grid would not be desirable as I’ll have to pay Western Power supply charge anyway.

          3 x 16mm2 cable has been brought from the meter box to where the house is.


          • Lawrence Coomber says


            You can easily offset the daily service fee through a very low FIT by a designed for that purpose sized on grid solution;

            Plus add a 3 phase off grid system for any night/day time loads, single and 3 phase to suit whatever you need to power.

            The advantage is you can have any size off grid solar array you want (up to 100 kw). Easily and cost effectively ground mounted and extensible. Solar PV is cheap at the moment – taking advantage of this point is sound thinking and good solutions design.

            Lawrence Coomber

    • Hi Lawrence,

      Our current consumption tends to be low around $240 every 2 months which includes supply charge, maybe slightly higher at this new house as it’s much more inland.

      If you can convince me of the economics of it then I’m interested.


      • Lawrence Coomber says

        Hi Ronald.

        Economically viable system design is everything: and hobby farmers have an advantage over normal domestic premises owners in that they have more available space and options for a PV Array area, and importantly can control both its ”structure type and orientation”.

        I have a 5 ha hobby farm backing onto the Condamine River. Hobby farm loads can add up quickly depending on the enterprise: [irrigation, machinery, workshop, welding etc]. In your case if you have completed a thorough daily load assessment, and you are happy with that, then the demand side kW can be ticked off.

        You emphasised outages as an issue you want to resolve in system design. Focussing only on your current spend of around &1500.00 per year for grid services and supply does nothing to address how to cost effectively design to mitigate outages. Not dealing with this situation in the initial system design would be a lost opportunity looking forward.

        You should discuss with your energy system designer a system specification that delivers the following outcomes:-

        (1) An On-Grid Inverter [1 or 3 phase] plus a Solar PV Array [PV1] sized to match the allowed limit of the network approval for Embedded Systems for your location, and bearing in mind the allowed limit of FIT kWh of your retailer. This Inverter’s primary role is to provide connection to the grid supply for feed into the grid rather than service any loads; its secondary role is to provide supplementary load supply only if and when that might be required [smart controls]. Shop around for the best FIT.

        (2) A Standalone Inverter [1 or 3 phase] and additional Solar PV Array [PV2] and Battery Storage [DC Coupled and working together as a single inverter supply source input to service both day and night-time loads; also [smart controls].

        (3) A 2.2 kW silent Honda petrol genset as emergency only backup to selected loads, plus consider a small VFD for some suitable services: water pumps etc.

        (4) Regarding the financial objectives for your overall solution: Your overall annual grid connected service should be 0 $ per annum or less outlay. The objective is to maximise the FIT available and minimise consumption [0 kWh or less is the goal] . Get this working right and on your current figures this means that you will save about $1500 per annum up front.

        (5) Maximise generous STC’s payment to system owners, by installing as much Solar PV that you can afford.

        (6) The final objective for your designer is to present a design spreadsheet that calculates to < 7 year payback overall.

        Note: Solar Arrays PV1 and PV2 are the one structure [but isolated], and managed by [smart controls]. This structure can also be multi-purpose [veranda or pergola or carport etc].

        A design that is easily expanded over time is very useful. The next owner of your hobby farm might be a pottery with kilns and heavy load equipment. High loads can easily be cost effectively managed in the Off Grid expansion.

        Best of luck moving forward with your hobby farm project Ronald.

        Lawrence Coomber

        • Hi Lawrence,

          Thanks for your response.

          We are in WA, so we don’t have a choice of providers. Current policy is excess power sold to the grid is only at 3 cents per kwh, so the objective of any installed system is use everything if you can.

          The only possible future consideration is if I acquire an EV.


          • Lawrence Coomber says


            Thanks for the WA heads up Ronald.
            Here in Qld I am on 52 cents FIT! was more when I started installing 60 cents.
            Recall an install at Coffs Harbour 10 years ago – 10 kW per phase on 3 phase system at 60 cents kwh. Over 20 k a year in FIT. But solar was expensive then.
            Have you considered moving east Ronald – we would be most happy to have you join us.

            Good luck with it all anyway Ronald.

            Lawrence Coomber

    • Haha, at my age, this will likely be my last house.

      Yes, I was on 49.5 cents FIT 10 years ago on a 1.5kW system. Lost that after 2 years as I was forced to sell my house, long story.

      Did think about moving overseas or to NZ post retirement but Covid mess that up! So we’ve decided to stay put in WA.

      I’ll be visiting Queensland late this year if travel is still fine.

      So, in summary, given the situation in WA regarding lack of FIT, my original plan is still the best one?

  2. Finn wrote>> The solar panels cannot charge your panels without the grid.

    That should be … charge your battery…

    Mine can, being off-grid 🙂

    • Finn Peacock says

      Typo fixed. Thank you!

      • So if I plan to build an off grid system it needs to be single phase?

        • Ronald Brakels says

          Hi Kelly, Ronald here.

          Off-grid homes are usually single phase, but if you need to run 3 phase equipment then 3 phase hybrid solar inverters are available, so it is an option.

        • Lawrence Coomber says


          If you are considering installing an Off Grid Standalone System at your premises you have plenty of options. There are both single phase and 3 phase inverters approved for solar system + battery DC coupled designs from 20 – 100 kW on the CEC Approved Inverters List at:-
 (under Product Type – select ‘Standalone PV Inverter’) and there are 48 Inverter models to choose from, that are all eligible for the creation of Government STC’s.

          Standalone PV Inverters are specifically designed for Off Grid Systems that include any combination of multiple DC source inputs including; Solar PV, Wind Turbine; Micro-hydro; Battery Storage for example.

          These specific for purpose design inverters also offer the advantage of a higher DC voltage input range which translates to lower DC operating current; smaller gauge DC input wiring, and extended battery life.

          Three phase is the better option for Off Grid generally as it can be used for any 3 phase equipment at the premises including; variable speed drive irrigation pumps, and equipment using 3 phase motors for example. If however the premises only has single phase loads to service, then a 20 – 30 kW Single Phase Inverter plus a 15 – 25 kW Solar PV Array (+ battery Bank) will provide a reliable and substantial 24/7 power supply.

          Your first task though is to have your premises surveyed by an experienced Off Grid system designer to identify what would be the most efficient and suitable system design to suit your individual circumstances.

          All the best as you move forward with your Off Grid project Kelly.

          Lawrence Coomber

      • Hi Finn, Thanks for the insights. Just about to make my solar investment. I have 3 phase power coming in and looking at a 10.3kw system. Option of 1 3 phase 8kw inverter (I realise this is smaller the the total system but due to direction aspects system will top out in frequently) or 2*5kw single phase units. I do want to plan for the future of batteries or to be able to go off grid – from what I have read the singles are the best option at this point in time. PS I have not 3 phase equipment and in NSW, cost are very similar. Craig

        • Ronald Brakels says

          Hi Craig, Ronald here.

          Normally I recommend 3 phase inverters over multiple single phase ones as they should be less affected by over voltage events. But if you are confident that over voltage events aren’t likely to be a problem in your area then the choice comes down to the inverters’ efficiencies, warranties, and cost.

          In the future when you get batteries your choice is likely to come down to an AC coupled system such as a Powerwall 2 that operates regardless of what type of solar inverter you have or you can replace your current inverter with a hybrid inverter and use that to integrate batteries. If you plan to get batteries soon you can consider getting a hybrid inverter, but if that’s not the case I don’t recommend one as it’s not possible to predict what battery options will be available years in the future.

      • Dennis Mitchell says

        I have an off grid situation, with no grid tie possible. I have also ordered a 3 motor Tesla Cybertruck that I would like to be able to charge via the off grid solar array and batteries. Cybertrucks are a huge draw of powerfor recharging. I’m thinking a 50 kw solar array with a 200kwh battery system might be enough to power this. The property is in SW Colorado with 300 days of sunshine. I have 10 acres on a south facing 40 degree slope with no shade trees in the area of the potential array. Your thoughts? I wondering if I can or should go 3 phase. I am a retired appliance repairman with mechanical engineering degree (should have studied electrical engineering!) I believe the Cybertruck has a 3 phase inverter between it’s DC battery and it’s three motors. I think all the motors are 3 phase in the Cybertruck but I’m not 100% sure. I’ve tried googling this question, but I have not found anyone who knows. Tesla does not respond to this question. I have accidently ordered a second 2 motor Cybertruck. I’m wondering if I could use that truck as the battery and inverter for the small 1500 square foot home that could charge the 3 motor Cybertruck. Do you happen to know what power requirements are required to charge or supercharge a 3 motor Cybertruck?

        • Ronald Brakels says

          You won’t need 3 phase power to charge a Cybertruck. If it turns out it allows faster charging you may decide to get it, but it won’t be necessary. I don’t know its energy consumption, but if the Cybertruck travels 3 miles per kilowatt-hour and you drive an average of 40 miles a day (14,600 miles a year) then you’ll need to charge it with an average of 13 kilowatt-hours a day. Since you have plenty of sunshine you’ll only need 3 kilowatt of solar panels to provide that. If you can plug the cybertruck in to charge for half the daytime, you’ll need 6 kilowatts. To keep it running in December by plugging it in for half the day you’ll need about 8 kilowatts of solar panels. You might want to go up to 10 kilowatts to be on the safe side. At current solar panel and battery costs its a lot cheaper to let solar energy go to waste rather than store it in a battery — although having batteries can be useful for other reasons.

          • Dennis Mitchell says

            Thank you Ronald for your input. I am thinking of using the second Cybertruck’s battery and inverters as the battery backup for the house. I’ve read that the Cybertruck’s battery is going to be over 200 kwh. They already have a “battery to three phase inverter” to supply power from the Cybertruck’s battery to the Cybertruck’s motors. I’m thinking I might be able to tap into that connection to supply three phase power to my house instead of to the Cybertruck’s motors. If anyone has any thoughts on this and whether or not this is possible, let me know. A Tesla PowerPack with inverter is over $120,000. A two motor Cybertruck is $50,000. Both have approximately a 200 kwh battery and inverter. I’m not sure what the Cybertruck’s inverter output is, but it must be substantial to power those big three phase motors that can accelerate the truck to 60 mph in under 4 seconds. I’m not sure if the Tesla PowerPack can be off grid, but I think it can. I think a Cybertruck would make an awesome off grid battery and power source if I can charge the Cybertruck’s battery off a large solar array either single phase or Three phase.
            The Cybertruck comes with 120v and 240 v single phase outlets in the rear of the truck for powering tools, etc. I’m not sure what the amperage output of those outlets are, but they are probably too small to supply power to a small house power panel. My home will use very little power, being south facing and mostly glass on the south side. It will sit at 9330 elevation; no air conditioning needed. I have a 10 kw single phase propane generator when needed. I also have a 250 amp dc gas welder that may be able to supply DC charging to a bank of house batteries batteries.

  3. Brian Davis says

    Hi Finn,
    Is it worth getting 3 phase power to take advantage of the bigger export limits,and the stability advantages you write about? I have also noticed that quite a few ground or air sourced heat pumps for heating and hot water are somewhat more efficient with 3 phase, or only come in 3 phase, so combined, I am wondering whether it is worth the installation costs?

    • Finn Peacock says

      It depends how much they are going to hit you up. Getting 3 phase on a new build is not much more than single phase. Adding 3 phase to an existing build can be very expensive – depending on your site. Your DNSP can quote you yo upgrade.

      Having 3 phase is going to become more important as the voltage on the grid gets higher (as more solar goes in) and as people need to charge their electric cars. And yes – heat pumps are a but more efficient with 3 phase.

      • Ian Thompson says

        Hi Finn

        A possible disavantage of using 3-phase inverters.

        I have 6.24 kW of panels arranged in 2 MPPT strings on an SMA 3-phase 5 kW inverter, installed nearly 2 years ago This worked very well at first, but as more and more houses installed PV, I noticed our power production was dropping very noticeably. On further investigation (using the Smart Meter, and the inverter’s read-out), I found the 3 phases were reasonably balanced in the morning and evenings (little PV generation), but during the morning 1 of the phases would go very high – approaching our 254 Vac regulated limit (240 V +or-6%). In the afternoon, another of the phases would approach that limit, but the 3rd phase would always stay at about 242 V.
        My inverter’s manual says that it commences throttling (or perhaps better described as limiting) at 250 Vac, and limits to zero output at 255 V line voltage. I was noticing our inverter was limiting ALL phases, if ANY phase was high. The current on each phase was the same.
        Seems like an opportunity lost – it would have been good for the inverter to redirect power on a high phase, to a lower phase – although I guess there maybe grid stability if all inverters had this feature. I can see it would make sense to the manufacturer, to design each of the phase inverter outputs to be rated at 1.67 kW (x 3 = 5 kW).
        But, if I had a single phase inverter, I could have simply swapped it to the consistently low phase, and all would have been good. Clearly, the PV generation on the grid was not being managed very well – and many 3-phase consumers were fitting single phase inverters to save cost (or – the installers were promoting this, to offer a better “package”).
        The Utility stated they were powerless to do anything – but appear now to have found a way, after I escalated this up to our Energy Minister.
        So – after experiencing equipment damage (CFL lights, motors, power supplies) from the excessive voltages (but within the regulations), and a loss of significant feed-in tariff, we are now back to where we should have always been.
        In this respect (Utility has little control over grid management), I suspect there is a weakness in the REBS scheme – management of the grid has been usurped by the installation companies.

        • Johann Holtzhause says

          I would install a “VARIAC” on the high voltage phase and feed in via the “VARIAC” which will match the inverter phase with the high voltage phase. Problem might be to legalise such a connection and might be more acceptable in a country where the authorities are not interfering too much.

          • Lawrence Coomber says

            Totally unsuitable Johann and non compliant with IEC 62109 regarding PCE equipment.

            No one should consider trying your idea. It is potentially lethal. Variacs are not isolated equipment and definitely unsuitable for RE projects.

            Lawrence Coomber

      • Bill Donley says

        Hi. Can you get a power wall to output 3ph 220v 30 amp power?
        My m
        Home shop uses a rotary phase converter. It’s old school and noisy. Planning on moving soon and want to go solar. Can’t get 3 phase from the power company. Just wondering if a power wall has this capability.

        • Powerwall is only single phase inverter. You can get a gateway, and put multiple PW2 across different phases. But I suspect that is of absolutely no use for you, as you need 3 phase power for this setup. In a blackout Tesla only support keeping a single phase up, even though you might have multiple PW2 spread across the phases.

        • Lawrence Coomber says

          Bill you do have PV power plant design options to achieve what you require, but more information is needed to evaluate your options accurately:

          Q1. What is the Home Shop power requirements (equipment (rating and phase), time of use (duty cycle), typical load demand etc)?

          Q2. You are planning on moving soon and want to go solar. What happens with the Home Shop then moving premises?

          Q3. Have you any details about the premises you are moving to? Unit, domestic house site, rural, block size etc.

          Simple points for sure but important ones that expose the scope of PV power plant designs to suit your objectives.

          Lawrence Coomber

      • Hi Finn,
        how does the 8.2 single phase inverter and tesla powerwall work in Qld on two phases, how is the powerwall charged by the extra output if its on another phase- or am I not understanding something?

        • The PW2 is only generates and charges on a single phase. HOWEVER, they have monitoring equipment, that can monitor up to 3 phases. With this, the PW2 knows how much is exported and imported on all phases, and can use this information to either generate or discharge power on the phase that it is connected to, to attempt to net the total across all phases to zero. With 3 phase power meters and billing in Australia, the meter will net this out to zero. So while there might be one phase that is exporting at any 1 time and 2 phases that might be importing, at any time this is netted to a single figure so the PW2 will always be trying to net this to zero.

  4. Mark Shueard says

    Hey Finn
    You didn’t touch on the other ( and BEST ) alternative, perhaps because it’s unusual for most people to have the roof space.

    I have
    3X solar arrays + 3X single phase inverters + 1X Powerwall 2 = bill bliss and I have Apocalypse Proof Battery Backup™ too.

    Not everyone has roof space for 3 separate arrays ( I have 57 panels ) but if there is the possibility of such a system it has one other benefit over a three phase inverter. REDUNDANCY

    • Finn Peacock says

      That’s absolutely a valid design and a cracking system. But it is much more expensive. In terms of hardware, 3 x 5kW single-phase inverters will cost about 50% more than one 15kW three-phase inverter. The inverter installation is 3x the work. And you don’t get the voltage and frequency stability benefits of a three-phase inverter.

      You do get the redundancy though – as you say.

      • Mark Shueard says

        I got lucky with the economics of all stages and I did not do it all at once.
        It’s worthwhile looking into if you have the roof space,.

    • Greg J Greet says

      I have a similar set up (3×10 panels) & 3 inverters which @ THAT TIME were not that much dearer. The other advantage of the setup was the internal resistance of the inverters was lower than a single inverter allowing lower threshold for energy capture &c.p. higher energy yeild.

    • WTF is apocalypse proof backup?

      • Mark Shueard says

        I was quoting Finn.
        It’s a funny way of saying you can have a blackout go indefinitely and still have power because the battery is charged by the PV system even though the grid is down.

    • Lawrence Coomber says

      Mark your energy plant setup sounds like a good opportunity to be further exploited, depending on your feed in tariff situation.

      Why not reduce your bill to $0.

      Consider Standalone Off Grid whilst maintaining your Grid Service (on no load) for 3 months to evaluate how your Off Grid Solution manages your premises usage needs.

      A 57 PV Module Array (add another 3 modules = 15S x 4P Array) is around 15+ kW which is the ‘sweet spot’ for an efficient 550 – 650 DC Bus Solution, DC Coupled with a 200 – 300 AHr @ 480 VDC nominal Storage Battery along with a single Standalone PV 20 or 25 kW 1 Phase Inverter; or 30 kW 3 Phase.

      The outcome would be a substantial and robust solution that would meet most needs, and most importantly for those occasional high demand needs that might not be met, don’t forget that for well designed Off Grid Solutions; “a little gasoline every year goes a long way”.

      Maybe something to consider at some point Mark.

      Lawrence Coomber

  5. Thanks Finn. I understand that Enphase is just in the process of releasing a 3 phase solution also, which potentially provides an addition option for consderation. This might also be critical for anyone who has shading issues.

    • Finn Peacock says

      Yes – the 3 phase component for Enphase should arrive is Australia any time soon. If you have shading you can also use Tigo optimisers on a string system. It is very cost-effective to selectively add Tigo to only the panels that get the shade.

      • “the 3 phase component for Enphase should arrive is Australia any time soon”

        I thought Enphase 3-phase components are available in market now. I am getting an installation done in next couple of days with IQ7+ Enphase mico-inverters with 3-phase cables and components.

        I hope the installers are not planning to use single phase components.

        @Finn is it possible for you to confirm the availability?

  6. Onya Gordon…. and I’ll bet you also don’t have harness your horse to Ferrari in case the price of fuel goes up.

  7. If I were in the market for a 3 phase solar or battery system, one of the things I would want to understand better is how they deal with unbalanced loads across the phases. Bear in mind that most of the loads in a domestic environment are single-phase. Only certain loads, like large air conditioners will be 3-phase. In a domestic environment I would say you are generally guaranteed to have the loads across the phases unbalanced. I would thus want to be certain that my solar and battery system can cope with that, and how efficiently they cope with that.

  8. I’m not an engineer but could you have a dummy load on each phase that automatically switches on when supply exceeds demand?

  9. I live in an area with very low grid reliability and 3 phase. So battery system with Apocalypse Proof Battery Backup is important to me. Because of that I thought it worth pointing out a couple of additional gotchas:-

    1. I suspect 3 phase solar inverters are always likely to be a problem if you think that 3 single phase batteries are the solution to allow the solar to work in a blackout with the battery for ANY solution that uses frequency shifting to throttle solar output. The problem is that in this setup, you would need to use frequency shifting on individual phases to make sure you can reduce solar output when needed and the battery and household loads can’t absorb all of the power. The problem with this is that when you do this, the 3 phases will enevidably move independantly and at some stage they will not be 120 degrees out of phase as would be required for true 3 phase loads. While a lot of use cases will not care about this if there is no 3 phase loads, I doubt any knowledgeable vendor or installer would want to install like this for fear that this might 1 day break a 3 phase load of an unsuspecting end user. Solution to this would be to use some other mechanism than frequency shift of throttling of solar output (and this would probably bring other benefits), but that does not seem to be the way the industry is moving at the moment, Of course the other option is 3 phase solar and battery inverters that can supply different loads to different phases in a blackout, and also charge the batteries from whichever phases have the spare solar power, but again I am not aware of any products that are doing this, and all the standards solar 3 phase solar inverters must follow is more about ensure equal output on all 3 phases for grid stability, which is totally unsuitable for islanded requirements in a blackout.

    2. For anyone thinking that the solution to get “Apocalypse Proof Battery Backup” setup is to use micro inverters on 3 phases, or even 3 single phase inverters to get the benefits of solar on 3 phases AND battery on single phase to give the backup. The problem is that AS4777.2015 has requirements that even single phase inverters must trip off if there is a phase unbalance. So technically Mark Shueard system if build today to AS4777.2015 requirements probably should have solar tripping off in a blackout. I am guessing that the reason it probaby works for him is that the solar is either pre AS4777.2015, or implemented in a way to get around this. But I thought this is worth pointing out, because it would be unwise for people doing this type of install to just assume it works. Same thing applies for micros, and new enphase micros in particular. I like many people have enphase micros install across 3 different phases. With my old M215 and old Envoy (pre AS4777.2015) each phase worked in isolation (solar could keep working on any phase that is up, irrespective of what the other phases are doing). But with newer S270 and new Envoy-S AS4777.2015 compliant setup, when one phase goes down, the whole system goes down. This is a massive “incompatibility” with the current AS4777.2015 standards that all grid connected inverters must comply and any requirement for the “Apocalypse Proof Battery Backup” that I really feel needs to be addressed in the standard.

    Finally Finn, I am curious about your comment to Marks post above that his setup “And you don’t get the voltage and frequency stability benefits of a three-phase inverter.”. Can you expand on what you are talking about there. When I 1st read, I assumed you might have been suggesting his setup did not address the voltage rise issue, but I would assume a 15kw 3 phase inverter would trigger exactly the same rise as 3 single phase inverters pumping out 5kw?? Or are 3 phase inverters somehow outputting between the phases, rather than between active to neutral. I have not got my head complete around it, but I guess if you are putting output between phases at 400v rather than between active and neutral at 230v that will be less current for the same output, which is less voltage rise??

    • Mark Shueard says

      While I have 3 x identical ( BOSCH ) inverters, 2 of them are pre AS4777.2015 profiles. The one that is running on the main load and battery phase is one of these.
      I too struggle to understand voltage shutoff /throttle / ramp up / requirements of the latest standard. One of these inverters meets that spec but has never shut off or ramped due to voltage. The other two have never shut off either, I have seen the main phase voltage at 256 V regularly and touching 258 at times, never shuts off.
      I too didn’t understand what Finn meant regarding voltage stability benefits, all I can say is I have never had any inverter go offline for voltage spiking.

      • All this is a complicated area that not many people understand well including a lot of installers (or for that matter myself so always good to find people who know the details and can reliably educate us all). The fact that you are using pre AS4777.2015 on your battery phase probably has the advantage that there is probably no chance a phase imbalance was you would experience in a blackout result in your solar not being able to work in a blackout. But there is the downside that this inverter and profile probably does not support frequency ramping (where solar output can be progressively throttle to balance generation and load). This does not mean you can’t use the solar in a blackout, but will probably just resulting in more “banging” the solar inverter on and off, something that some people have had some concerns might impact the longevity of the inverter.

        BUT, having said what I have said above, irrespective of what it says in AS4777.2015 about the requirement for even single phase inverters to shutdown on phase imbalance, I would not be surprised if that is often not implemented in single phase installs, and especially if they are not all done at the 1 time. I suspect this would be very easy for the install not to do. As near as I can figure out, to do this, you would need to install a bunch of extra stuff to even know that there was a phase imbalance which would not normally be provided with a single phase inverter install. So apart from complying with an overly draconian standard, there is probably very little reason someone on the cold face would want to go to the effort. You will probably find that the main target was micro’s which are more commonly spread across 3 phases in 3 phase setups. And so my guess those responsible for the standards where probably more interested in checking that people like Enphase had this implemented, and in truth with the centralised management that comes with systems like Enphase, it is probably more easy to implement. Doing so with single phase inverters is really a can of worms that would easily be circumvented by installers or home owners anyway.

        Voltage issue is way more complicated in the standards that a simple “below X volts is ok, and above X volts is ok”. This is probably made confusing by the fact that the profile information you see, often does not tell you all the detail. From my limited understanding (that might not be 100% correct), is there are a few things that pretty rigid (like voltage most be below 253v for inverter to startup etc). But beyond that it is more complicated. Some examples :-
        1. a lot of the voltage thresholds are based on 10 minute averages. So just because you see a temporarily higher voltage, does not mean it has to act on it.
        2. there are things like “volt watt mode” which will commonly not see the inverter switch off until voltage is 265V and this can be increased. See So it is possible that your AS4777.2015 inverter was throttling, but not shutting off??? In fact it might even be tweaked so that even at 258v the throttling might be minor enough for you not to notice even if you were looking.

        But if I were you, and you voltages of 256v and 258v were not purely due to voltage rise (which will be there whenever your solar is exporting), I would be getting your supplier to tap the voltages to you down to be within the standard below 253v.

        • Mark Shueard says

          Only the battery phase reaches 258V , the other two do not, they reach 252V.
          It is of note also that when my battery was re-installed in July ( swapped out a Sunverge for Powerwall) the installer swapped the phases around so he had red instead of white as the main phase. ( maybe he likes red better than white ). At the time, I though that is weird but if you have a colour fetish no problem , go for it. Then after he left I remembered that the white phase had the lowest voltage and that now my battery phase went from the lowest to the highest of the three phases in voltage. I’ve been watching it and being ready to ask them to come back if I got PV shutdowns – but so far I have not seen it. I do not believe there has been any throttling either on any inverter.

          I tested blackout and it performs as intended, phase 1 PV still functions ( only when battery is over approximately 80% full by design apparently ) and charges the battery.

    • Mark Shueard says

      “”Or are 3 phase inverters somehow outputting between the phases,””

      Yes, each of my systems is on a separate phase, by compliance and SAPN approval requirement.

      • That comment was really a question to Finn about 3 phase inverters (you have 3 x single phase inverters). Single phase inverters output between Active a Neutral, with I assume each of your single phase inverters connected to a different active phase (Neutral is common). I assume 3 phase inverter is effectively the same, with 3 active phases and 1 Neutral. But this might be a bad assumption on my behalf and it could be that is outputs Phase A to Phase B, Phase B to Phase C and phase A to phase C. When you go phase to phase the voltage is 400 odd volts (not 230v), and this might have benefit for voltage rise (but I don’t really have my head properly so thus why I thought I would ask Finn, who might be across this better).

    • Ian Thompson says

      Hi Matthew

      What do you mean by ” uses frequency shifting to throttle solar output.”, please?

      I’d have thought it impossible to shift frequency, as the outputs are all locked solidly to the grid frequency?

      Maybe you mean “phase and voltage shifting”? I’m somewhat familiar with off-grid variable frequency drives – these synthesize a.c. from a d.c. supply, usually by a method of switching rapidly with PWM then smoothing – these vary the effective voltage to prevent over-current and saturation of motor and tranformer core components – and could be locked to a grid frequency.

      I’m finding my SMA solar inverter tends to output near-constant current per phase, with very little variation with phase voltage differences. So – if one phase goes excessively high, the 3-phase inverter will throttle back all 3 phases to curtail output – then throttle up again when the excess voltage is removed – 3 x single phase inverters wouldn’t work that way.

      BTW – I’ve never had my inverter switch entirely off (except at night), as no phase voltage has every exceeded 255 volts (but has got very close to this, when the entire inverter throttled back to about 1 kW total output).

      • “What do you mean by ” uses frequency shifting to throttle solar output.”, please?”

        Let me explain.

        You are 100% right that when connected to the grid, the grid controls frequency and solar or battery inverters must play along with those frequencies. HOWEVER AC couple batteries use frequency adjustments to control solar PV inverter output IN A BLACKOUT. So the game completely changes when you have a blackout and effectively the battery operates in a completely different mode. Solar grid tied inverters are actually designed at their heart to always be connected to the grid, and always shutdown when the grid goes down. They are either :-
        1. connected to the grid and trying to output as much as possible while not exceeding voltage thresholds.
        2, shutdown when the grid is down.

        But if you have an AC coupled battery, the story completely changes. In a system that supports battery backup in a blackout, in a blackout, the 1st thing that happens is the home is isolated from the grid, and the battery starts generating power to supply loads. When the solar PV sees this, it thinks it is the grid and can start and do its thing. But it has no idea the grid is down and as far as it is converned the grid is connected and it can operate exactly as it always does. But this causes a problem if it is outputting more than the battery and home loads can soak up. The battery inverter is designed to only output what is needed to supply loads in the house and no more. But the solar PV is designed to put out as much as it can. If this exceeds the power requirements in the house you are going to get voltage rise and spikes in the house which can be bad for appliances. Sure the solar PV will throttle when the voltage raises, but these values and response times are slow and not good enough to control voltage in an islanded home (PV assume it has a grid connected which would normally soak these excesses up and prevent the voltage rise, and in this configuration you only need it to respond slowly to voltage rises). So AC batteries without some mechanism to control solar PV output could be extremely problematic.

        Fortunately the AC couple battery guys know what they are doing, and the battery has a few mechanisms to be able to take responsibility for voltage regulation in the isolated home in the blackout and control not only its output, but the solar PV output. There are a number of tricks they have up their sleeve :-

        1. when the loads increase and voltages fall, the battery simply increases output to balance supply and demand (up to the kW capacity it can output).

        2. when something in the home shuts down or solar PV output increases and voltage rises, the battery can throttle back and even absorb any excesses by charging the battery (up to the charge kW capacity of the battery).

        3. a good quality battery inverter/charger is extremely fast and can respond to these things very fast and deliver good quality power.

        4. when the battery is full, or there is excess power even when the battery is charging at full speed, the battery (which is simulating the grid and setting frequency independently from the grid because at this point it is not connected to the grid) has a few tricks up its sleeve to regulate solar output. Because all grid connected solar inverters in Australia must support various versions of AS4777, they can use the mechanisms in there to control inverter output. The main mechanism they use is to shift the frequency up and down to regulate solar output. When frequency is set high enough this will cause the inverter to shutdown. Later versions of AS4777 require inverters to be able to ramp output down in a more granular way as frequency progressively rises up, which gives the battery even more options to try to balance supply and demand than the older solar PV inverters that could only be on or off.

        Generally the battery will always ensure it has some room to both charge and discharge the battery to it can take the fine grained control of balancing house loads and generation as it fluctuates. It can’t count on the speed of controlling the solar PV, so this is a more granular mechanism, and also means that batteries and solar need to be carefully designed to not overload the ability of the battery to control supply and demand.

        This last mechanism is what I am talking about when I say ” uses frequency shifting to throttle solar output.”. It is only used by the battery when it is not connected to the grid and thus needs to take control of solar.

        What you are witnessing with your SMA 3 phase inverter having some output on all phases, and even throttling all phases when there is high voltage on 1 phase, is due to the design on the 3 phase inverters and some AS4777 rules which REQUIRE 3 phase inverters to output equally on all phases. It is a little more complicated than that now with some new modes when allow this rigid rule to be bent a tiny bit. But fundamentally, 1 of the downsides of 3 phase inverters as they are currently designed and probably more importantly regulated, they will never support solar PV in a blackout for a couple of reasons :-
        1. if the battery is only a single phase, unless all 3 phases are kept up, then the solar PV inverter MUST shutdown under AS4777 (I am guessing most 3 phase inverter are designed that they could only do this even if AS4777 allowed the to do differently),

        2. You could have batteries and solar on all 3 phases, and this might enable you to get around the issue above. But while you use frequency shifting to control solar PV, this is going to cause a range of issues in 3 phase environments. A few of these include A) 3 phase require all phases to be 120 degrees out of phases. So you can no longer use frequency shifting on a single phase to control solar on that phase, without throwing the other phases out.Ok, I hear you say, why not shift frequency on all the phases so it is kept in sync. But as soon as you do that, you have lost the ability to control solar individually on each individual phase and thus it all falls over.

        But this is all complicated, and I have given you the simple version. So the really simply versions is that your 3 phase solar PV is never likely to work in a blackout even if you have a battery that support blackout protection. If blackout protection for your AC coupled battery purchase and being able to run the solar in a blackout is important to you (and I would suggest it probably should be, because as it stands battery economics will not pay for itself for the vast majority of users, so one of the main reasons to justify a battery is blackout protection), then you will probably want to steer clear of 3 phase solar PV inverters. I doubt this will change any time soon, and it is VERY unlikely that any 3 phase inverter on the market today will support some new battery that is yet to be developed to change this. At some stage down the track there might be completely new 3 phase solar PV inverter designs and changes to AS4777 to give better 3 phase battery backup support. But I would not hold my breath, and suspect these are more likely to be a hybrid inverter or strongly integrated solution between battery and solar inverters to get around the limitations of frequency shifting and AS4777.

        I personally see the whole 3 phase inverter vs single phase inverter question a lot more complicated than “3 phase good, single phase less good”, Truth is it is a lot more complicated than that and there are some significant pros and cons on both sides. Because of my battery backup requirements, 3 phase inverters are simply not an option for me personally.

  10. Ian Thompson says

    From experience, I feel you’ve got it wrong. I had an SMA 3-phase inverter fitted, and it throttles if ANY ONE of the phases goes high. We had 1 phase go high before noon, another at, and after noon – so a lot of throttling. Like many (most?) people, I rely on the feed-in tariff to make PV economic, as we use most power morning and evening, when PV is not producing. One of our phases was remaining significantly lower – so if I had a single phase inverter, I could have had it moved onto the lower voltage phase.

    • Finn Peacock says

      Have you checked your consumer mains and if it is not your fault (less likely to be you if you have a 3p inverter) asked for the DNSP to tap your local transformers down?

      • Ian Thompson says

        Asked all that – my meter was logged, not my problem – suggested local transformer tapping change, but Utility (via Energy Minister) said that couldn’t be done, and nothing could be done as they would go outside regulations through low voltage in summer at the end of the line – I went back (through the Energy Minister) to say I was disappointed, as their own logging showed 1 phase low, so if they shifted generation from other phases, to this phase (called “NETWORK MANAGEMENT”), then everyone would benefit – the Utility said they couldn’t do this, as the consumers decide where their PV generation goes, and changes may upset their (3-phase) equipment, and would have to be done by contract electricians at the individual consumers homes (at their cost). Talk about a wonderful management system! I did point out the Utility could ROTATE the phases going into a 3-phase home (with single-phase PV), to bring the generation onto the low phase.
        No, they couldn’t do anything, except perhaps tinker with the HV feed line transformer tapping. Time passed….
        Now months later, even with the increased generation the phases are much better balanced, and throttling problem seems solved (for the moment – infill housing and more PV penetration may re-create the problem).
        I’m thinking the Utility responses may have been CYA – and the Minister may have directed them to sort it out.

  11. koen weijand says

    you forgot to mention 2 more advantages of 3 phase inverters.

    3 phase inverters have the average panel voltage near ground, while in 2 phase inverters the average panel voltage is around half the dc value and has a grid frequency component. this means that there could be ac GFI trip problems, for example during rain and thin film panels with higher capacitance to panel ground.

    the other advantage is reliability . there are less capacitors needed in a 3 phase system, due to eased ripple current requirements. that is why 25kW, 3ph inverters are manageable in size and cost.

    • Ian Thompson says

      Hi Koen

      Do you have a link to explain how 3-phase inverters provide an average panel voltage near ground, please? On an off-grid 3-phase inverter I have, the incoming d.c. maintains charge on a bank of input capacitors, the -ve side of which is referenced to ground – in which case the panels would have full d.c. on one end of the string, and the other end would be at neutral voltage, which in our MEN system would be near enough to ground potential?

      Not sure your reliability argument is valid – agree the d.c. ripple current in a 3-phase system will be less – but if you reduce capacitor numbers, the reliabilty doesn’t change (less ripple current, but less capacitors to share it over). In fact, 3-phase inverters have 3 times as many “pass” components (IGBT’s, or MOSFETS, plus drive circuitry). My schoolboy statistics suggest that 3 times as many parts increases the failure rate by square root of 3 = 1.732. In other words, unless the intrinsic reliability of the components is increased (by oversizing, or better quality), the failure rate of any one of the 3 parts together will increase by 73% – most likely then taking out the entire unit.

      I feel sure 3-phase inverter manufacturers will have chosen their parts, to achieve a MTBF of about the same level as single phase inverters – albeit at increased cost.

      Similarly, 3 x single phase inverters will have a failure rate 73% more (for any one of the 3 inverters failing), than the rate of any individual inverter.

      This is of course, if my schoolboy understanding (in fact, University educated, but recalling from the mists of time) is correct.

  12. 3 phase battery inverters? I can’t find any directly but I can’t see any reason why you couldn’t use a 3 phase solar inverter with batteries that are set up with a high enough output voltage. It’s just another DC source and provided it’s in the right voltage range it should work. Right?

    • Square peg in a round whole.

      Solar inverters tend to be designed to just pump out maximum power all the time. Battery inverters tend to have a bunch of extra smarts to enable sensible control of how the battery is discharged. eg balance demand in the home and things like TOU etc. With Australia’s limited FiT for most people there would be no point in discharging the battery flat out and exporting excess power to the grid from the battery etc.

      Then there is the fact that battery inverters often include battery chargers etc, that solar inverters will not have etc.

      • Agreed and valid points. Still not seeing these mythical 3 phase battery inverters anywhere except as part of a 3 phase hybrid inverter.

    • Lawrence Coomber says

      Mondo – can’t find any 3 phase inverters for your battery storage integration?

      Check the CEC approved inverters list. There are several models up to 100 KW both single and three phase designed for DC multi input sources designs precisely for the scenario you have described.

      Select in Equipment Category Dropdown: “Stand Alone PV Inverter”

      These inverters are designed for multi DC source integrated inputs in the form of a DC coupled (any DC sources including solar PV) backbone. Very reliable and enduring and works well with battery storage systems around 480 VDC nominal, and any battery chemistry stack or super capacitor or combination of DC inputs works perfectly.

      These higher voltage systems are very efficient and have many advantages over lower ELV battery voltage (< 50 VDC) the foremost advantages being higher voltage battery stacks = ratio-metric reduction in discharge and charge current; much smaller gauge wiring; much improved system safety due to lower current; and most importantly, extended battery life through lower current charge and discharge designs.

      Higher voltage battery stack designs are only for experienced and qualified DC power system engineers and system integrators Mondo. These qualifications are best achieved through investing in formal training courses with the EV industry in Detroit, or selected large scale battery storage manufacturers in Shenzhen who operate in this space such as Sunwoda, Optimum Nano, or Leoch.

      Lawrence Coomber

      • Careful. Your recommendation to look for “Stand Alone PV inverter” I assume are only suitable for “off grid” applications?? I don’t believe these inverters are suitable for grid connected applications. Note blog article is only talking about grid connected applications and I assume Mondo’s requirement is for grid connected application??

        But look at Lawrence’s list for grid connected batteries, and you will find 3 phase solutions there. But be careful, as I don’t think u will find any solution for 3 phase battery that works with existing grid connected solar inverters in a blackout that rely on frequency shifting due to issues previously outlined. Theoretically I can’t see why it would not be technically possible to build such a battery inverter. But it would need to charge/discharge 1 battery, and have chargers and inverters that can charge/discharge at completely different rates on all phases at all times. But even if this was technically possible to build, and commercially economical enough (ie can be built at a price to create enough demand for someone to make a profit), I suspect the way that AS4777 etc is currently written would preclude that. I would say all of this will be solved at some stage in the future, but I suspect with the current lack of battery economics, and thus limited demand and market for batteries, this might be a little way further down the road.

        • Lawrence Coomber says

          Yes correct Matthew.

          These listed inverters are for Off Grid solutions only, as well as those premises that want to install a completely separate and fully isolated Off Grid system onto their premises in addition to an On Grid system.

          This strategy is becoming very popular in managing single or specific circuits that are high demand such as irrigation pumps; factory rotating machines and equipment and in rural applications.

          The extension of this strategy allows for those businesses/premises that have a largely daytime operation to operate their circuits Off the Grid during the day and the completely separate and isolated On Grid system is reserved only for lesser night-time load circuits such as fridge, security lights etc.

          Lawrence Coomber

  13. Ian Thompson says

    Everyone is talking about batteries as some sort of Nirvana.
    They must all be very, very big users.
    My use is modest – any I find from a detailed look at our consumption profile, that we would only save less than one-third of the cost of the battery pack, over it’s projected lifespan – on top of that, it is big money up front, and I haven’t even figured in the lost opportunity cost of the extra inverter(s), battery chargers, and the installation cost. Financially, for me at least, an extremely backward step.
    Going off-grid saves the connection fee, but extra inverters, because the grid-tied inverter has regulated anti-islanding features and will not run unless the grid voltages are present. Not sure if on-grid, the inverters would operate from a high voltage (350Vdc?) battery – but would like to know.

    • @Ian Thompson

      That’s the thing about the Tesla Powerwall, it will keep the solar inverters up (while the sun is shining) and powers the house while the grid is out. If there is excess solar, it will top up the battery. The Tesla Energy Gateway manages the grid connection and will island the house off the grid whilst keeping the inverters running (both the solar and battery inverter). The battery becomes the grid reference for the solar inverters, so they think there is grid power. When it senses grid mains has returned, it will reconnect the house back to the grid so that you can continue to export your excess solar or import power depending on the loads and supply.

      The battery in the Powerwall is 50Vdc.

      • Ian Thompson says

        Hi Graham
        You may have misunderstood my words – maybe instead of saying I’d only save 1/3 of the battery cost, I should have said I’d only recover 1/3rd of the cost. After 10 years, I’d be out of pocket to the tune of 2/3rd the initial battery cost, plus the cost of installation and anything else required.
        Just doesn’t make economic sense.
        P.s. our Utility supply is very reliable – although I accept this is likely to be degraded with increased proliferation of domestic PV, unless more inertia and expensive synthetic inertia is added to the grid (e.g. SA, which has nearly twice the tariff that we have).

        • ” although I accept this is likely to be degraded with increased proliferation of domestic PV, unless more inertia and expensive synthetic inertia is added to the grid (e.g. SA, which has nearly twice the tariff that we have).”

          I would not believe everything you read, especially if it is coming from a COALition or Murdoch media.

          While there are many widely circulated anti renewable myths, these are not born out of the reality. eg :-
          1. that the only way to have stability in the network is to have a lot of traditional spinning inertia (coal and gas). That Luddite argument used to have a full stop to it, but now even those who wanted to make that argument have had to change that full stop to a comma and suggest that the synthetic inertia is expensive. But the facts don’t bear that out. The big SA battery has allowed for a reduction in spending on FCAS services to be reduced from $109m in 2016 and 2017 to a forecast of just $3.6m in 2018 (ie more than 96% reduction in the costs). See A large part of this will be the fact that keeping large amounts of traditional “inertia” in reserve for FCAS services is significantly more expensive than what it costs to provide it via what you call synthetic inertia, because “synthetic” inertia can respond much faster, and in a much more meaningful way. Sure some of this cost reduction would also be nothing to do with that, and more as a result of the batteries ability to break the energy companies pricing cartel for these services. But that too is just as relevant, and I would expect to bring the same benefits as we install more distributed solar and batteries so bring to again reducing the cartels pricing monopoly and improve the supply and demand balances which allows the cartels to game the market to their profit.

          Other references to this point :-

          2. SA power is expensive / unreliable because of large concentration of renewable power. Fact, SA power has always been expensive, long before the transition from coal to renewables. Fact the recent blackouts in SA were triggered by failures of coal and failures to bring gas online in failures and storms blowing down inter connectors. None of the expert reports are blaming renewable for the recent blackouts as near as I can tell.

          This reference covers most of it better than I ever could :-

          3. We need coal and gas for reliable network. Not even the head of AEMO thinks that. ( Or the Finkel review or others actually dealing in this area.

          Unfortunately the COALition and Murdoch media continue to sow the seeds of FUD until it just becomes accepted and repeated fact by too many people unfortunately.

        • I should also add, I totally agree about your sentiments about the prospects of many people being in a position to make an economics return from batteries as it currently stands. I could not make the economics add up even before the significant Tesla PW2 price rises, and much less after it. So for most people, without special circumstances, or significant subsidies, if the only reason you are getting batteries is to save money, there is probably a LOT of places you will find a better ROI (eg solar). But I suspect this is because most people are only using to load shift power usage, and there is not enough arbitrage between FiT and peak rates to justify.

          So when used like this, we have to wait for electricity prices to rise, and/or solar FiT to fall, and/or batteries costs to fall, or longevity to significantly improve before this changes.

          HOWEVER, when the market develops, and we are able to sell battery services at a premium for things that batteries are actually good at, this could quickly change. eg if we sell some of our battery usage to provide FCAS services, or during peak wholesale prices, and or to soak up extra power at times of low demand to discharge and help the grid at times of high demand, we could potentially be paid enough to change the economics substantially. But it does not look like we are there yet, without significant subsidies, or using assumptions that are unlikely to pay out. When the government and regulators are committed to the RE transition, I am sure they will start working the regulation that will promote this, and the investment required, but until then we are stuck in a nightmare of our own making (ie high electricity pricing living in one of the most energy rich nations on earth).

          • Ian Thompson says

            Hi Matthew

            I’d like to go one step further…

            To me, installing Solar PV, or adding a battery, should not necessarily be just about achieving ROI on the purchase cost – which as you say might have to await a significant subsidy, or for the price of power to increase.
            In my (non-self-centred) view, the economics of using a given technology should include recovering ALL of the associated costs – including the value of any subsidies (e.g. REBS), since after all, these are still costing us our tax dollar. Also, if the technology introduces undesirable features (e.g. the need for FCAS services, or an increase in the cost of power, or requiring an otherwise unnecessary increase in grid capacity), then these are costs that also need to be included.
            I agree that batteries are not “there” yet – except in certain special circimstances (TELSTRA have been using Solar and batteries for years in remote areas – very, very expensive, but cheaper than transporting diesel and servicing remote generators).
            I would dearly like to “load shift” our solar generation – today, we will produce around 37 units of power, but will use about 6-8 units overnight (lights, TV, cooking, refridgerator). Our tariff is about 26 cents/unit, FiT ~ 7c/unit, so every “shifted” unit will save 19 cents – not a lot, but it all adds up – just not enough to justify a battery system.

  14. William ANDREWS says

    Hi Finn, 3 Phase sounds very complicated. If I had a single phase system with enphase micro’s, would I be able to install an apocalypse battery later? Bill WA

    • Ronald Brakels says

      Hi William, Ronald here.

      Yes, that is possible. The Tesla Powerwall 2 is an example of an AC coupled single phase battery that can be added any time and can charge of solar panels during a blackout. (Unfortunately it is difficult to get and has just gone up in price.)

    • Actually, the devil is in the detail on this 1, as to if it will work with an apocalypse battery or not. If you have 3 phase, and you install Enphase today it is VERY likely that it will not work with a battery in an apocalypse!!

      I know this because I am in this position, and have so far battled unsuccessfully to get this working. Problem is there are parts of AS4777.2015 that mandates even single phase inverters must shutdown on phase imbalance. It is Enphases implementation (which technically they must as I understand it to be connected to the grid in Australia since Oct 2016) that causes the problem. It is hard to get detailed information on exactly how they implement this. But it is almost certainly the Envoy-S that implements this, and commands the micros to shutdown when it detects a phase imbalance. Now if you have 3 phases, even if you convince your installer to only install the micros on a single phase (probably only likely if it is a very small system, otherwise your distributor will want you installing the micros across multiple phases to keep balance), it is still likely they will sell and install the Envoy-S which measures and gives you consumption stats across the phases (you will probably want this as well as it is really handy to understand your usage). When they do that, it will be connected to all 3 phases to measure the consumption, and I would be pretty confident that it is this that enables them to detect a phase imbalance and then they must shutdown the solar.

      If this issue was easy to solve, I am confident it would have been solved. I initially had a deposit and install scheduled with 1 of Enphases largest installers in Australia, with the assurance this would work (despite making my concerns VERY clear and pointing them at the area in AS4777.2015 which would appear to cause the problem). But eventually they twigged to the issue, and after almost 6 months of working with Enphase for a solution, decided to return my deposit and did not want to play any more and said it could not be done. I have now gone to a new installer, who said if needed, they would work around it by installing 3 individual Envoy-S if they need to to make it work. I am now installed with a single Envoy-S, and sure enough, no support for Apocalypse battery (ie if 1 phase goes down, all phases go down). I was installed over 3 months ago, and still have payment outstanding because it was agreed this would be resolved before completion of the project. They tried to tell me “Enphase was aware of the issue, and had a profile they could install when the battery was installed” and suggested that was enough to get their last payment. But I smelled a rat on this 1, as they could not give me ANYTHING to support this claim, and so far refused to install that profile and test. Last communicate with them is they will get onto Enphase again, and try to arrange for this to be done, but that was over a month ago, and I still not have heard anything.

      There is a solution that does work. And that is to install a pre AS4777.2015 profile, and then it does work fine. But technically I suspect this is not supposed to be done, and does have 1 other downside. These profiles do not support frequency ramping (ie progressively being able to throttle output as frequency rises. The PW2 and other frequency ramping battery solutions use this to control the solar output, so that they have a better chances of keeping the solar on when the battery is close to full and being able to supply household loads from solar. Battery should work without this, as PW2 will just raise frequency till the solar trips off, but this will lead to more cycling of the battery and banging the solar inverter on and off, which long term might not be good for longevity of the solar inverter.

      I could believe solution might be to install multiple single phase Envoy-S and micros and have NO phase coupling between phases. Expensive and probably not as nice as single Envoy-S as I assume production and consumption usage will be 3 separate systems rather than presenting a consolidated view. But I am also suspicious that there might even be issues with this in certain circumstances where for example you have a neighbor with phase coupling or similar. There is lots of evidence in Enphase’s install documentation can happen. I did also wonder about all sort of ways to work around it in install. eg having Envoy and phase coupler on the grid side of the gateway which isolates battery and home in a blackout, and thus impacts ability of Envoy-S to send instruction to shutdown micros. But that testing shows that it is WAY more complicated than you would think, and despite doing this, somehow the micros were still detecting phase imbalance and shutting down.

      Story is different if you have an only Enphase system (per AS4777.2015 as I do). Despite being installed across multiple phases, it does not need the Envoy to work, and will all work without an issue on phase imbalance. But of cause you have the same limitation I have outlined above with lack of support for progressive frequency ramping of solar output.

      I think the issue is really with AS4777.2015. When it was written, it is clear to me that it was not written with any thought for batteries, and certainly not apocalyptic batteries. I suspect the standard really needs to be updated to better allow the inverter manufacturers to cater for this. More attention needs to be brought to this issue, because I am sure there are a lot of people buy micro solar on the assumption this will work, and it does not. Just like people surprised when their 3 phase solar inverters do not work with their shinny new battery in a blackout.

      Anyway, my council, if you are planning an Enphase micro install (or any micros for that matter as I think the issue is not Enphase but AS4777.2015), AND 3 phase, AND you want a battery that can keep the solar going in a blackout, proceed with extreme caution. oint out the issue to any potential installer, and get them to agree you will only pay once you have tested apocalypse battery support. To test that, you don’t need a battery. You just need to shutdown 1 phase, and confirm the micros on the other phases do not shutdown.

      • Finn Peacock says

        How big is your system?

      • Lawrence Coomber says

        Matthew rework you battery storage from AC coupled to an independent and isolated solar PV DC coupled off grid solution working “in tandem with -but not connected with your existing system” and controlled by third party “remote smart monitoring and controls”.

        The loads circuits distribution between two or more power systems is managed and optimized dynamically by the monitoring and control system.

        Think more clearly about your energy solution objectives and imperitives from a clean slate perspective, and discuss this with you energy systems design engineer.

        Lawrence Coomber

      • A quick update on the post above. Eventually the installer / Enphase did come through with a profile labeled as AS4777.2015 that did allow 1 phase to work when the other phases are down. So this would work with an apocalyptic battery on a single phase of a 3 phase enphase solar setup (obviously only keeping solar going on the single battery backed up phase). And hopefully it also does ramping of output with frequency to make it even nicer for any apocalyptic battery setup. And hopefully it is also AS4777.2015 approved and not just a dodgy ‘fix’ to shut me up. But it is there if u can get your installer to give it to you.

  15. I read your post again, and might have misinterpreted your question in my previous long reply. If you only have single phase power at the property, as Ronald says, you should be fine if the installer installs solar and battery to support this. Single phase certainly simplifies thing as long as you are not limited by its limitations (ie more restrictive rules on how much solar and battery you can have).

    My concern in the previous post was to point out the potential problems if you actually have 3 phase power at the property, even if your Enphase and battery is only installed on a single phase.

  16. New Envoy-S / S270 micro system is 10kW. But I suspect it would not matter how big the system is if it is using Enphase micros and Envoy-S and monitoring 3 phases. Micros are on 2 phases. I can shutdown a phase with no micros on that phase and it will shutdown the micros on the other 2 phases.

  17. Hi Finn and all,
    This has been a very interesting discussion. One thing that has been alluded to, but I am not sure I have seen (or maybe understood),is whether it is “better” to to have a three phase system use micros (Enphase IQ7 & IQ7+?) spread across one or three phases, or use string inverter(s) with or without optimisers? I am at the point of deciding on a design, and the options can be a bit confusing 🙂

    The issues of apocalypse batteries is an interesting one, although with the payback value being negative on most of its functional life, that is maybe less appealing. Having some power during a blackout would be nice, but I have generally very stable power locally, so it usually doesn’t happen much or for long.

    • Ronald Brakels says

      Hi Brian

      For an unshaded location the cheapest option is solar panels without microinverters or optimizers. For a shaded installation the decision is a little more difficult as it may be more cost effective to install more panels than use either microinverters or optimizers. It is possible to put optimizers only on panels that will be shaded and keep costs down that way. The economics of microinverters tends to work better for very small systems than larger ones. Where microinverters and optimisers excell is where a homeowner wants to get the most generation possible out of a limited amount of space. Especially if it is difficult to install panels at the same orientation.

      As for backup power, having a small generator can be more cost effective and (hopefully) reliable option. One reason is there may not be much energy left in the battery when a blackout occurs.

  18. Hi Ronald,

    We have a U shaped house, and the current 10KW designs we are looking at have panels on the East and North, with both aspects having two separate locations, depending on the system parts, and not all aligned vertically down the roof. There is capacity to have West facing panels as well if wanted. Shading isn’t really an issue – our own trees being the only likely shading, other than weird roof angles casting shadows during the morning or afternoon.

    Going three phase potentially lifts the 5KW export limit (for what that is worth, and presuming solar feed split across the phases), and prepares for things such as car chargers, heat pumps, etc, along with the improved voltage stability as per the benefits outlined by Finn.

    The cost of the system jumps about $2.5k going from mid range panels (Jinko 315W JKM315M-60) with a Fronius string inverter, to the same with Enphase IQ7 Micro Inverters, and then markedly ($6K more) stepping up to a tier 1 panel (LG NeON R 350W) with the Enphase IQ7+ Micro Inverters. Pretty much the same price between using the top panels with the micros or the same using a SolarEdge with P370 Power Optimizer Models.

    And the generator options does seem like a pragmatic approach 🙂

    • Lawrence Coomber says

      Brian when the time comes to think more about those higher consumption “potential day time services load circuits” consider expanding the solar PV DC Bus and running an autonomous “daytime off grid circuits” solution for greater cost effectiveness independent of the grid, and particularly the advantage this strategy offers for DC Coupling for charging battery storage for dynamic controlled night usage.

      Lawrence Coomber

  19. Smart Net Meters automatically redistribute the solar onto all phases nowadays.

    You don’t need a 3 phase inverter.

    For spinning disk meters, yes you do, but not for the modern smart net meters.

    Finn, please do your research!

  20. Ian Thompson says

    Hi John
    Are you sure you have your facts correct? I have a 3-phase Smart Meter, but there is no way on earth that it redistribute power across phases to do this, it would need to be the size of, and have the capabilities of, 3 x single phase inverters – at least.
    What it does do, however, is to record the inports and exports occurring on each of the individual phases.
    I do have a 5kW 3-phase inverter – but this outputs essentially the same power on each of the phases – so as far as the meter is concerned, each phase may, depending on its individual load, be either importing or exporting power.
    To me an opportunity lost – as it would be nicer for power exports (from house to grid – their import) to be biased towards the lowest voltage phase – to introduce a degree of balancing.
    As it is, an excessively high phase voltage will cause the inverter to throttle back ALL phases, or trip out altogether.
    Our provider reads the meter – and we get get a FiT benefit for net exports across ALL phases – and of course get billed for the net sum of all phase imports.
    On reading another blog – I noticed the salesman, despite being repeatedly asked, did not answer the question about phase balancing – just answered the other questions in such a way that may make someone think he was confirming the phase balancing issue.

  21. koen weijand says

    As zero injection in spain means zero in each of the phases, 3phase zero injection is almost practically impossible (limited to the lowest load per phase). I asked fronius tech in germany about unbalanced zero injection options , but the three phase inverters always put out a balanced power. so the only way to zero inject 3phase according to spanish law is to use 3 single phase inverters with 3 smart meters. spain energy companies are strongly linked to politics , always good for 200k/an for a retired politician. the boss of iberdrola salary is 42000 euros/day (yes day !!)

  22. Ian Thompson says

    Hi Koen
    Wow, you’d think with tge EU propping up Spain, that sort of largesse would be deemed criminal!
    When you say “zero injection”, I guess this means it is illegal to export any power to the grid (and you have no FiT).
    Seems crazy – Iberdrola could make money out of re-selling green power, at a significant mark-up.
    What you say about 3-phase inverters balancing their power output is one of the reasons I’m not so sold on them. You only have to lose any one of the phases, and the whole PV system will shur down – no solar savings until restored. Or, one phase goes too high, and all phase outputs throttle back or shut down until rectified – similar to you zero injection configuration.
    In reality, a 3-phase inverter is similar to 3 x single phase inverters in one, I’d think – just slaved together, and sharing a common dc supply. It’s a pity they don’t provide for a degree of optional “steering” between phases.

    • koen weijand says

      recently since a government change it is now much easier to connect PV (autoconsume) as long as you do not inject. the administrative and technical hurdles to be able to inject are huge, but not impossible.
      same reason why there are no EV chargers in public streets. selling electricity is strictly regulated . giving away is allowed so modern supermarkets have chargers for their customers, but roadside chargers are rare. also because the connection rate is 50euro per kW per year, one of the highest in europe.

  23. Hi
    Find your site good
    Have 3 phase with 1 phase inverter which has failed due to over voltage by energy supply
    needing replacement
    looking at 3 phase as I want to add more panels in the future plus batteries
    what do you recommend
    please help

    • Ronald Brakels says

      Hello Allen

      If your inverter was under warranty you may be able to have it replaced as you are protected by Consumer Guarantees regardless of what your written warranties may say. Grid over voltage is a fact of life in Australia and it is reasonable to expect inverters sold here to be able to withstand it. (It is possible to make a claim under Australia’s Consumer Guarantees if the inverter is out of warranty but that is more situational.)

      There is a graphic on this page here:

      Showing inverter brands we consider reliable and well supported in Australia. (It is below the graphic showing solar panel brands.) I believe all of these have have three phase inverters. If you are looking for a high quality inverter that will allow flexibility with panel additions then a Fronius inverter would be a good choice.

      If you just want to replace your inverter at the moment you can go to our homepage and enter your postcode in the space at the top right:

      Then select “Maintenance or upgrade of existing system”.

      However, it is often more cost effective either install a second solar system or replace the old one altogether than to upgrade an existing system. Because of this you may want to consider:

      1. Replacing your old solar system entirely with a new large one. This can be a good choice if your current system is small and old.
      2. Replacing your old failed inverter with a similar sized single phase inverter and then when you want to expand install a second new system with a 3 phase inverter.

      If you do decide to expand your existing system you may want to consider replacing the inverter and adding additional panels at same time as this is generally cheaper than getting them done separately but one of the two options above will usually be more cost effective.

    • Ian Thompson says

      Hi Allen
      I have 3-phase, and when purchasing a PV system, specified 3-phase inverter (SMA – rated at 240Vac) – installed 27 months ago – because I thought this was the responsible thing to do (to help balance the phases).
      Initially regretted my decision, as 2 phases were reaching over 254Vac, and the third remaining at about 243V. The higher phase voltages were often initiating throttling of the inverter – which acts across all 3 phases – and was reducing my generation and export capacity.
      If I had a single phase inverter, I could had moved this onto the lower voltage phase to prevent early-onset throttling.
      However, I can say this:
      1. 3-phase inverters cost more.
      2. A 3-phase inverter will still be exposed to excessive voltages.
      In my case, I contacted the Utility – who logged my meter but concluded they couldn’t do anything without other consumers at “the end of the line” going below the minimum allowed voltage.
      From inspection of or local grid I didn’t believe this – so escalated my request through our local minister – who wrote to our Energy Minister – after all, all of us were paying for additional parasitic losses and suffering premature equipment failures unnecessarily.
      Got a response that appeared to me technically inaccurate (easy answer!), so went back a 2nd time – when the Utility told the Energy Minister they couldn’t do much, but would attempt “tweeking” the sub-station voltages.
      Took quite a long time – but guess what?
      This morning, our grid phase voltages all hovered around 236Vac, and yesterday at midday they ranged from around 240 to 244Vac !
      Both days have been hot, and cloudless.
      So – it might be worth challenging your Utility to prevent a repeat of your experience. I like Ron’s suggestions as well.

    • Ian Thompson says

      If you go 3-phase, you will need to either put batteries (plus charger, etc.) on 1 phase, or else have 3 sets of batteries – as best I understand.
      Would appreciate comments from Finn or Ron on this aspect.

    • If you want to have the ability to have blackout protection AND keep AC coupled solar running in a blackout, you should avoid 3 phase solar inverters all together as the solar will not work in a blackout. Single phase inverters will be a better fit of this if required. Even micros will need a very particular profile which you should make sure your installer will provide for you if and when you get a battery. If they don’t know why a micro systems installed on 3 phases will not work in a blackout, and why they need a very particular profile to allow it to work, find another installer.

      If you don’t care about blackout protection, or happy with blackout protection from the battery only without solar support, a 3 phase inverter will be fine for this.

      • It’s been a few months now since anyone’s posted here about 3 phase inverters and “apocalyptic battery backup”
        Could someone let me know if the newer Goodwe 5Kw AC coupled BMU 100a auto charger or the older Goodwe GW5000S BP would be a good solution to integrate with a 3 phase Fronius Symo 15.
        System is grid tied, no 3 phase loads on the home but the board has been wired to spread the house load evenly on all phases.
        If battery backup in a black out and charging of the batteries using solar during an outage is not cost effective (ie using one of the above mentioned products or similar) would re setting my board up so that one phase is a “backup” phase be the most cost effective option?
        Can someone also explain what’s needed to prevent the solar from feeding into the grid during a blackout? How is this safety requirement overcome?

        • Lawrence Coomber says

          P South you have made some good points:

          But a better approach is to not try and design a power plant by what you believe to be the limitations of the key system components equipment or designs. You are guaranteed to end up not getting what you want going down this track.

          Explain precisely what outcomes you want your power plant to deliver you as the customer, and let those out there who are interested and operate in this space explain to you what’s available in hardware; software; system controls and system designs to achieve precisely your goals. I would be surprised that the outcomes you are looking for would be unable to be fully satisfied if you spell out those outcomes clearly.

          Power Plant systems design is a topic in flux and ever changing, and the practitioners are best placed to advise.

          Lawrence Coomber

        • It is pretty simple answer about if your 3 phase inverter (or any other 3 phase inverter) will work in a blackout with an AC coupled battery. I am not aware of any 3 phase solar inverter that will work in a blackout, and I do not expect this to change anytime soon because of a range of technical challenges I will not repeat here. I would not expect this to change until someone specifically designs a solar inverter and battery to design around these challenges. But this would be complicated by the need to get around very specific AS4777 requirements which would seem to work against allowing this to work (read AS4777 would very likely need to be updated to make it even possible to have an approved inverter to be connected to the Australian grid).

          Any grid connected battery system that can work in a blackout will need a thing called an ATS (Automatic Transfer Switch) somewhere. Its job is to isolate the house from the grid in a blackout. In the case of things like Tesla Powerwall, it is build into the gateway. Other products would all be the same. But because it is often built in, there might be no mention of the ATS in the marketing material.

  24. thanks I have been told a 3 phase inverter will work with my existing panels and will balance the output over the 3 phases

    • Ronald Brakels says

      Hello Alla

      A three phase inverter will work with existing panels provided there are enough panels and they are wired up in such as way as to meet the 3 phase inverters requirements. If the 3 phase inverter is the same capacity as your old single phase inverter there is unlikely to be a problem but it is important to check as they can and do vary.

      A 3 phase inverter will work to balance output over the 3 phases. Because of this it can help avoid, or at least lessen, problems caused by grid overvoltage which can cause your solar inverter to either ramp down its output or temporarily shut down altogether.

      • Ian Thompson says

        Hi Ron

        With respect, I have to largely disagree with your comments about 3-phase inverters helping avoid or lessen grid overvoltage problems – at least in regard to my SMA 3-phase inverter – and I suspect all others.
        From careful monitoring, my inverter tends to output approximately equal CURRENT into each phase – if anything, putting very slightly more current (and therefore power) into the higher of the phase voltages – although this effect is small.
        So, it cannot avoid high grid voltages except by throttling back output over all 3 phases, if one of the phases goes high – perhaps caused by the Utility transformer settings, or because neighbours have single-phase inverters on that phase, or that phase is more lightly loaded (or a combination of these things).
        It will lessen overvoltage caused if you have high impedance supply lines – partly because the current is shared over 3 lines intead of 1, but otherwise, again if the high grid voltages are externally generated (as was my case until the Utility finally addressed the issue), the inverter can only deal with overvoltage by throttling back output, or shutting down altogether (hasn’t happened to me, but I’ve heard stories from others).

        I do agree that if everybody had 3-phase supplies, and all used 3-phase inverters or single-phase generation was carefully balanced across the neighbourhood, and grid loads also remain balanced – then 3-phase will help the cause. That is the only reason I went for 3-phase.

        • Ian, by extension wouldn’t that problem be excaverbated on a single phase inverter where you are diverting all the amps to a single phase?

          • Ian Thompson says

            3 factors Mondo:

            1. My experience in the suburbs is that the incoming line impedance is relatively low – so that the main impact is caused by a high local grid voltage, brought about by too much distributed generation on that particular phase, or an unbalanced load, or as in my case (I believe), too high a tapping on either a local, or a sub-station transformer.
            2. Due to the low line impedance from home to grid, dividing the current by 3 will of course have a small beneficial effect, but in my experience this was absolutely swamped by the inbalance in the grid phase voltages. With single phase on a 3-phase supply, you’d do much better by swapping to the lowest voltage phase, rather than using a 3-phase inverter (which will be prone to throttling).

            Having said all of the above, one of the things I noticed, was that one phase had excessive voltage in the late morning, and another in the early afternoon – seemingly caused by how West and East oriented PV systems are connected to the grid. One of my phases remained consistently low, which is what I would have connected to if I had a single-phase inverter.

            The best outcome (which I managed to achieve, albeit a difficult process), is to have the Utility fix the problem. We regularly had phase voltages all over the place (badly out of balance, and often exceeding the throttling voltage of 254 volts), whereas now the voltages range between 236 and 244 Vac, and are seldom more than 2 volts different.
            3. You really need to know what you’re dealing with, and either seek help from the Utility, or otherwise probably stay with single phase if the phases are badly imbalanced by either loading, or PV generation – or both.

            That’s my view, anyway.

        • I agree with Ian’s reservation about 3 phase inverters. But my primary reason is because I value the ability for current or future batteries to support be supported by solar during a blackout. This will likely never be possible with current 3 phase solar inverters with any battery system that uses AC coupling and frequency shifting to control solar output.

          But to expand the discussion on the voltage issues Ian outlines with 3 phase inverters, which is potentially a real concern for some users, there is some rays of sunshine on the horizon. AS4777.2015 does have option for “Voltage Balance Modes”, which some 3 phase inverters might (or might not) implement to practical benefit of people in the situation that Ian outlines. Ie the inverter is allowed to output more current on the low voltage phase. I have no idea if any actually implements this, as I am guessing implementation would add to the expense and complexity of the inverter (I have no idea if it would be trivial or significant). But if they do, and if this implementation is flexible enough it might allow for full inverter output in circumstances that some 3 phase inverters can’t and provide the added grid benefit of working in a very practical way to help balance the grid which is a service that goes beyond the home owner.

          By my way of thinking, I can’t help by think that we have an ever growing pool of both solar and battery inverters that can either be problematic to the grid, or a BIG part of the solution, and a lot of it comes down to what is written in AS4777. I can’t help but think a bit of an update there to better balance the requirements of the end user, to the requirements of the rapidly changing grid could be of great benefit to all parties. I am no expert, but I suspect things that need to be considered :-
          1. Mandating the support of “Voltage Balance Modes” which has the twin benefit of help end users with grid over voltage issues on 1 or 2 phases but under voltage on others, as well as helping balance the grid for everyone. Of course the cost implications of this need to be considered, and if too expensive, it should be optional, with a requirement for vendors to clearly say at point of sale if this features is supported.

          2. putting sections in to better allow connections of batteries and support for solar in a blackout. eg allow 3 phase inverters to continue to output on a single battery backed up phase in a blackout where the other phases are down.

          Anyway, the issues are not trivial, so good for sights like Solarquotes to contribute to the dialogue and shine some light on the issues.

        • Ronald Brakels says

          Assuming panel capacity is the same a three phase inverter reduces voltage rise caused by you own system. Also, depending on local conditions can potentially benefit from lower voltage on one or two of the phases.

          That said I would consider looking at the additional cost of a 3 phase inverter and then trying to decide if it would be a better investment to put the money into a larger single phase solar system. (Potentially making use of export limiting to increase its capacity.)

      • Ronald, the wiring on the panels is generally the same for single phase or three phase inverters. Most higher rated single phase and three phase inverters would have 2 DC inputs but a lot of systems are just wired to a single DC input. The only proviso being that the new inverter has the same DC voltage range as the old one. For example my old single phase Sunnyboy had an input range of 140V to 500V for the MPPT and 600V max – my new Solaredge 3 phase inverter is pretty much the same although it doesn’t give a minimum voltage, probably because it uses panel based optimisers

  25. i have a three phase 10kw fronius symo, it is a three phase inverter but one of the phases that has been used to connect it to out power box is the tarriff 33, so initially we had trouble with the ripple control shutting down the system when the tarriff 33 went off but now im finding that when the solar is producing energy it is sending most of it back to the grid, we have three meters for our three phases, tarriff 33 which we do not use at all during the day, another tarriff 11 meter which does not use much power during the day and another taffiff 11 meter which even with the solar producing 8kws during the day is still importing 2 – 3 kws per hour from the grid, im guessing because the other power being generated is going off to the grid via the other two phase meters, just wondering if i put a single 3 phase meter on instead of having three seperate meters if this would spread the power out better and give me more solar gain instead of it all getting exported ( though this would mean i would loose my tarriff 33)

    • Ronald Brakels says

      Hi Stephanie

      A three phase solar inverter will typically try to export solar electricity through all 3 phases. I assume the phase currently on tariff 33 just has a normal meter that isn’t able to record exports. If so your inverter could be sending surplus solar down that resulting in you losing a portion of your solar feed-in tariff. If this is what’s happening and you get a single 3 phase meter then, with a 10 kilowatt solar system, I would say you should save about $1 or more per day on your electricity bills.

      If you get a single 3 phase meter you can put what is currently on tariff 33 on a timer so it will switch on during the day and so mostly use solar power. With a timer you can adjust yourself you can make sure your hot water system — or whatever you may have on tariff — always receives enough energy.

  26. We are having a house built on the Fraser Coast

    The proposal includes
    7.98Kw SE8000H Inverter and Optimisers with export limiting,
    The decision to opt for a system of this size, (rather than say a 5Kw), was made in an effort to offset the power demands of a proposed 16Kw ducted air conditioner.
    The selected aircon system requires a three phase power supply.
    I am trying to establish if the entire output of the Solar PV system is available to power the air conditioner.
    Does the single phase inverter supply power to all three phases or to only one phase?
    If the answer is only one phase then would that mean that power for the other two phases going to the aircon will always be entirely supplied from the grid?
    If so should I insist on a three phase inverter?

    • Ronald Brakels says

      Hi Max

      The good news is the entire output of the solar system will go towards meeting the power draw of your air conditioner before any grid power is used.

      A single phase inverter will only supply supply power to one phase, but your electricity meter will look at the power being exported by the phase your solar system is on and subtract that from the power being imported on the other 2 phases to determine how much power your home is using. For example, if the phase with the solar inverter on it is exporting 4 kilowatts of solar power while the other two phases are importing 2 kilowatts each of grid power, then as far as your electricity meter is concerned your home is using no power at that time.

      Note that a 16 kilowatt air condition supplies up to 16 kilowatts of cooling but its electrical draw should only be around 4 kilowatts when operating at full power.

      Because you have three phase power I suggest looking into getting a three phase inverter. This means you won’t have to export limit and your solar panel capacity can pretty much be whatever will fit on your roof.

    • Hi,

      I have a SolarEdge inverter with optimizers. Ask your installer to look into Jinko and Trina solar modules with Maxim Integrated optimizers. These are tiny ICs (integrated circuits) built into the solar panel itself.

      Each of these manufacturers should have something available. In addition, Jinko has a back “thingy” with 3M sticky tape which has intrigued me, but I am not sure if it is offered with the IC optimizers.

      Maxim claims to have have a similar performance as hardwired optimizers on the back of solar panels, and they could, also, have a price advantage.



      • Thank you Eric.

        The proposed system is 7.98Kw using a Solar Edge SE8000H Inverter and Optimisers mated to 28 x 285w Q-Cell panels

        • Hi Max,

          You are welcome.

          I have a similar 3-phase setup as your proposed system. My array is about 10% larger than the inverter’s nameplate capacity.

          Somethings to keep in mind with the SE inverter-optimizers: in the future if you want to add a battery system, then you are boxed into a particular set of options.

          If you want to expand and add DC or AC coupled systems, then your options need to consider the first system.

          The cost for using these optimizers was about 20%, if this is a concern, then the Maxim route opens up other inverter and battery systems solutions.

          Another issue I have is that any software changes need to go through the installer. Other inverters may or may not have these problem; however, keep in mind that your control and interaction with an inverter is through software, and some companies provide more of an open access to their customers.

          If you live in a remote area, like I do, this could be an issue.



  27. I keep,running into these wisdom good nuggets.

    I for one I am thankful for the article.

    I have been thinking lately of running a second, independent, 3-phase hybrid inverter precisely due to the difficulties exposed here.

    This second inverter would have its own set of solar panels. The purpose of this second system would be mostly for self consumption. The hybrid inverter I have in mind has the ability to limit exports to zero, and it would be DC coupled to a battery for emergency power.

    The one issue I have is there would be two solar systems behind the same grid meter, and I have not thought out yet all of the possible issues coming my way.

    Would you mind pointing out any obvious minefields associated with this behind the grid meter two solar system setup?



    • Should be no issue, and lots of people including myself have multiple solar systems. They don’t really need to know about each other. If you need to do export limiting, they probably all need to support export limiting, and be configured so the total export limit is not less than the sum of the 2 export limit on each system.

      The only thing I can think of, is were you wire the non hybrid inverter with relationship to the hybrid inverter. Using a hybrid inverter and DC coupling the solar and battery avoids some of the downsides of AC couple solar and battery. Ie for the right setup solar and battery should restart when the sun comes after a flattened battery, and you avoid a whole can of worms with no support for 3 phase solar in a blackout you have when you AC couple solar and batteries. But you will want to make sure that the old solar inverter is not connected behind the backup circuit, unless you hybrid inverter supports AC coupling.

      I would look closely at your battery options. More of the better priced solutions seem to be favoring AC coupling and the simplicity of AC coupling means that I would not be surprised if this is the way the market continues to move. But not if you go with 3 phase inverter, you will probably preclude yourself from AC coupled batteries in the future and having solar running in a blackout support. This technical limitation with 3 phase inverters and AC coupling is the primary reason I would think twice about 3 phase solar.

      • Dear Matthew,

        You could be right regarding the battery issue since my choices are limited to the much smaller set for which my inverter of choice is compatible,

        My first choice is the Fronius Symo Hybrid 3-phase inverter. It has the ability to play nice with my existing FIT grid tied 3-phase solar system (AC coupling).

        It seems to be able to limit the export of excess energy, and it, also, works well with my current house 3-phase electrical system, and in addition, it has an accessible software interface to change parameters.

        An energy export limitation will be of importance for this second system since my utility has changed the ‘rules of the game’ since I installed the first system.

        My utility is now paying less for energy fed into the grid than for energy that I consume under the new FIT rules, and it has added, also, a net metering scheme.

        I have at home both a consumption and a production utility meter, and at this time I am not sure how they would work out the actual billing under a net metering scheme.

        In addition, I have discovered that this new set of rules strongly encourages self consumption of energy to make the economics work on my favor. The above mentioned inverter has many user friendly options for this purpose.

        Both the (unknown to me) new billing of energy and increasing my level of self consumption of energy are new rules to which I am trying to adapt as best I can.



        • koen weijand says

          as FIT schemes are becoming worseover time, selfconsumption and feed in limiting becomes more important. the smart connection of storage techniques like heat pumps will determine the choices of inverters. many heatpumps have only target temperature as input control parameter. only recently in germany there are developments of integrating household equipment into the loop.
          when the storage equipment like heatpump is singlephase, 3 single phase inverters may do a better job for unbalanced loads in a 3phase connection.
          in spain for example, zero feedin in a 3phase system means zerofeedin current in each of the phases. so when there is an unbalanced load,the feedin for a 3phase inverter needs to be set at the lowest current of one of the phases.

          • Koen,

            I find the work with heat pumps (both for hot water and space conditioning) a great breakthrough in efficiency.

            I recently found a hot water device called an energy diversion device that follows quite nicely the contour of the solar production curve. Whenever energy was available it would kick in to divert a little bit of energy for hot water.

            It seems to be able to do this by monitoring all the energy loads and all the energy production. When enough energy is available it goes to work.

            I have seen something similar to this with some of the inverters, but they still require external devices. I wonder if they will one day make this a part of the inverters.

            I for one would like to see this capability for both hot water and EV charging as part of the inverter’s capabilities. It could simplify the path from generating the energy to using the energy efficiently.



          • koen weijand says

            SMA is leading the efforts by adding EEBUS HVAC functionality to their homemanager.(

            they already had incorprated the stiebel eltron heatpump connection.
            Many heatpump manufacturers will jump the EEBUS bandwagon,and we can see heatstorage as an addition to battery energy storage. you can store energy in a radiating energy storing floor,(you can increase the energy storage capacity by adding phase change materials to it), or in a hotwater tank, used for heat exchange for shower water or low temperature floorheating.similarly the floor can also be used for cooling.
            controlling the power drain of the heat pump is essential,and can only be properly achieved by frequency regulation of the compressor speed.
            then the dynamics of controlling all this such that there are no instabilities, are a major challenge.
            The high thermal mass of the floors,added to proper insulation and low heatloss allows to overcome the night’s ,and you can pump up your floor during the PV day.

          • Hi Koen,

            The site had no reply button for your last comment. So I am doing it here,

            I appreciate the sharing of this information. It makes it seem so much simpler. I don’t know if you ever read the adventures that some of the early off grinders went through back in the 1960’s and 1970’s, but they would have probably felt real groovy with such a setup just as I would.

            My one concern as I read your comment was regarding condensation when cooling the floor. How are they getting around those little drops of water?

            In any case, the depth of the integration level is absolutely amazing.

            I will share in return with you a little video that I recently watched on my favorite batteries.

            How the heck did we ever deviate away from such a path?



          • Hi Eric – no reply button on your post with the YT link about batteries.

            The simple answer to your question “How the heck did we ever deviate away from such a path?” is that we found something much better in terms of bulk and weight in the various Lithium chemistries. Lithium is the lightest metal in the periodic table and as such offers the most Wh per kilogram.

            The claims about Nickel Iron batteries longevity are vastly overstated – you’ll get just as much life out of LiFePO4. Beware of the battery salesmen selling snake oil 🙂

          • Hi Mondo,

            I am not entirely convinced that we really found something that is much better.

            A Nickel Iron battery will degrade over time due to use and temperature just like any other battery such as a Lithium battery.

            However, suppose you spend $20,000 of hard earned money into a battery bank which you expect to use over the next 30-years.

            A Lithium battery bank with luck will degrade about 30% every 10-years, and a Nickel Iron battery bank will degrade about the same amount.

            With the Lithium battery bank you will lose another 30% at the end of the second decade, but with the Nickel Iron battery you dispose of the liquid inside the cells.

            You wash the inside of the cells (the electrolyte), and with about $30 dollars worth of new electrolyte you pretty much have a new battery ready to start its second decade.

            The electrolyte can be neutralized with an acid (like vinegar) since it is alkaline, and it can then be safely disposed.

            At the end of the second decade you will feel lucky you spent $20,000 in Lithium batteries, and you will go and buy a new Lithium battery bank. In absolute terms it will be cheaper than the original battery you bought 20-years ago; however, because of inflation and depreciation your money will be worth less, and it will be equivalent to spending another $20,000 from 20-years ago.

            The buyer of the original Nickel Iron battery bank with a clean electrolyte inside will go do nothing else since his battery bank is still working fine thank you very much.

            In terms of progress try to understand who bought the original Edison Nickel Iron battery, and why did they close it shortly after buying it.


            It had nothing to do with progress, and it had to do everything with profits.

            Therefore, as you stated “Beware of the battery salesmen selling snake oil.”



  28. Lawrence Coomber says

    3 phase inverters used in solar PV and battery systems is a considerable leap forward over 1 phase systems from both an engineering perspective in every category, and equally importantly a system cost benefit analysis.

    There is no functional penalty for 3 phase end users only gains, and also opportunities not available in single phase systems for polyphase machinery circuits and other equipment including ovens etc.

    3 phase solutions are a must have in rural PV and battery solutions (either on or off grid – or both which is becoming a popular configuration in rural situations where irrigation pumping is common) but may not be in such high demand in domestic installations yet, but this will change.

    Energy systems design engineers don’t have to look any further than the fact that compared to single phase circuits three phase circuits provide 1.732 time more power with the same current, and this provides for considerable cost savings that migrate thru the overall system design because: reducing the system current requirements reduces cable sizes; circuit protection devices; and wasted energy by reducing I2R (copper) losses due to heat.

    The same efficiency and cost benefit gains applies also to battery DC sources as well, with system design trends now to lower the current from unsafe and dangerous levels and increase the battery storage voltage considerably to more efficient values. Fronious Symo Hybrid inverters for example, accept a 400 VDC battery source input but are only compatible at this time with Fronious Solar Battery; LG Chem HV; or BYD BBox.

    Off Grid 1 or 3 phase solar PV and battery solutions that I am involved with since 2010, operate at 480 VDC nominal at proportionally less current than 48 VDC solutions for example, which provides a huge system safety and functional benefit overall.

    Lawrence Coomber

    • I am not sure the statement “There is no functional penalty for 3 phase end users only gains,” holds true in call cases. For example, if you want a battery that uses AC coupling (eg Tesla Powerwall 2), a 3 phase grid tied solar inverter will never be able to work with this in blackout. Sure, you can ignore the AC coupled battery solutions and go for DC coupling / hybrid inverter solutions. But currently from what I can see in terms of bang for $ in terms of $/kWh, decent kW output including in a blackout, decent battery recharge speeds, UPS failover times, supporting existing solar etc, currently for grid connected people the AC coupled solutions are winning in the bang for $ race. And as soon as you go down that path 3 phase solar inverters are not going to work in a blackout.

      So as with all things, it comes down to your priorities and requirements and as near as I can tell it is all a compromise. It is just about knowing the pros and cons of each approach.

  29. koen weijand says

    on top of that 3phase inverters have
    – less ripple current in the capacitors, such that a longer life can be expected
    – less problems with PVcell leakage currents as the average AC voltage on the panels is zero.

  30. Lawrence Coomber says

    I am a bit off the 3-phase topic but anyway….

    Fair comments Matthew but that’s not where it ends.

    You have exposed some features (or lack of) that underpin the immutable concept of obsolescence in all technology design, PCE being in the spotlight at the moment.

    You are by default, a player and influencer in promoting obsolescence in PCE design in fact, by presenting well-structured and logical technical arguments to other practitioners and end users as you have on this particular Solar Quotes blog topic.

    Along with millions of other Matthew’s globally; collectively that’s what drives design change.

    Power engineering technology design is rapidly evolving as we all know, and it is fair to say that everything on the shelf today is obsolescent already (not obsolete though just yet). That is why we see a continuous stream of new models of PCE released every other week. If you followed the global PCE/Battery Technology Conference/Exhibition circuit like many practitioners do, you would see this unfolding from exhibition to exhibition at astonishing pace.

    But having said that, it is useful to understand that commercial manufacturing imperatives demand volume markets to survive and to also ride the sales wave until it is exhausted. iPhone might be an example of this in play. Design manufacturers are more reactive to external forces than proactive internally including PCE, and the downside is that some “entrenched old design chestnuts” can hang around too long, which is what happens until some company “breaks-out” a new innovative PCE design concept that integrates and controls DC coupled higher voltage Battery Storage and Solar PV with smart PCE, which is not yet mainstream design in grid tie technology, but unfolding incrementally.

    Back to your comments. What you are really describing is that current PCE is not dealing efficiently and as well as it could be from an end user perspective, with the integration and management of Solar PV and Batteries (the System DC Bus). For those of us who are involved with PCE design and manufacture this is definitely the case, and it has been an embarrassing sticking point for PCE design engineers for several years for a host of reasons, one being that PCE design manufacturers are not battery design manufacturers as well, nor are they systems integrators, and this point has prevented best engineering practice integrated designs from being seriously considered or getting any traction.

    Tesla broke the mould though and recognised this key point from an EV perspective and vertically integrated as both PCE and Battery designers and manufacturers. All of the necessary tools were finally in the one toolkit. Tesla was therefore in the right place to float similar EV PCE design principles across to stationary RE battery storage applications. You will recognise the same outcomes from BYD; from EV’s to BESS.

    Over a short 3 year span I recall being involved with 48 VDC EV battery stack drive trains through to working in Detroit last year on 900+ VDC battery stack drive trains. This should tell you something about BESS technology concepts moving forward.

    So there is a lot of EV power-train technology concepts packed into a Powerwall. But there is still a long way to go (but the sales wave is not yet exhausted). Tesla needs to be very cautious and not get to comfortable with their BESS though, it is a long way behind world’s best practice design and functionality for what customers need globally. The same immutable laws of obsolescence apply to Tesla as they apply to any other technology company.

    So what might all this mean for traditional PCE designers/manufactures like SMA; Fronius etc who don’t have the EV connection in play. Amalgamations and takeovers will be the norm, and the EV industry will overwhelm the PCE industry and dominate this space in the near term.

    Lawrence Coomber

  31. Hi,

    I live on Bonaire an island in the Caribbean. Our power is 3 phase 112-127V, 50Hz. Our home has a mix of 127V and 240V outlets with the aircos, refrigerator etc on 240V, lights etc on 127V.

    We have a large unshaded south facing roof with a 9 degree inclination. The utility has just started to allow grid tied systems. Power costs 30c/kW/h and the Feed in tariff is 5c. So solar seems an ideal option.

    I am considering a 27 module system with three single phase inverters. People who have had these installed are suffering from premature inverter failure.

    After reading this blog I am rethinking and considering a 10kW three phase inverter.

    Would currently available 3 phase inverters play nice with our 112-127V/240V 50Hz grid?

    Thanks for any advice


    • Ronald Brakels says

      I’m afraid I’m not familiar with your grid. Here I would recommend a three phase inverter over 3 separate single phase inverters, but I don’t know what is available where you are. Since you are in a humid location I definitely recommend using PID resistant panels.

    • Looking at the voltage in Bonaire, single phase is 127VAC 50Hz and 3 phase is 220V AC 50Hz. Which makes sense – 127V on a single phase you would not get 240V on 3 phase. (127V x √3 = 220V approx).

      If lots of people are having failures with single phase inverters most sensible course of action would be to find out why before purchasing any inverter. Is it the local grid causing inverters to throttle? Is it a particular brand of inverter? The salt air and humidity?

      Ron’s right about not knowing enough about the local situation but in general it’s cheaper to buy a high quality 3 phase inverter over 3 high quality single phase inverters. I would definitely be doing my own research and writing to manufacturers about whether their three phase inverters cover your grid voltages.

  32. Lawrence Coomber says

    Koen yes good points.

    And particularly more relevant in off grid solutions than on grid of course, as the System DC Bus (PV + Storage eg) can be easily and more efficiently exploited without compromise in an overall power system design.

    Integrating self managed Solar Thermal closed heat exchange systems in best practice off grid solutions is a must have for sure, as are variable frequency drives, on any and every water pumping application.

    Lawrence Coomber

  33. I feel like my original goal got sidetracked.

    I am still trying to find a solution for using Nickel Iron batteries. Battery banks made from these batteries usually have a voltage of 12, 24, or 48-volts.

    The 3-phase inverter that I like from Fronius (Symo Hybrid) seems to work well with battery banks charging at high DC voltages of several hundred volts.

    A different 3-phase inverter from MPP solar works well for charging batteries at 12, 24, or 48-volts minus all the bells and whistles of the Fronius inverter.

    In addition, I need to make an AC coupled installation due to an older existing solar installation, and both of these inverters will accomplish this.

    Would anyone have any recommendations one way or the other?

    Best regards,


  34. Eric – that’s rose coloured glasses stuff. You can’t just replace the electrolyte because the other components in the battery wear out as well. That’s called entropy. Same as the electrodes wear out in a lead acid battery, the electrodes wear out in a nickel iron battery.

    What’s more they have a number of serious disadvantages for home storage over competing technologies.

    Here’s an information page I found from a power and solar company detailing the issues (and positives) with NiFe batts. Saves me doing it. It also details why you’re having problems finding any equipment designed to support them.

  35. Hi Mondo,

    This guy has lived with his family off grid for decades (first in Colorado and then in Hawaii). They have relied on batteries for night power for many cold winters.

    He is on his second set of NiFe batteries. The first set he owned of NiFe batteries (from Hungary) used to foam due to oil floating over the electrolyte and reacting while it off gassed. He left all his energy systems with most of his belongings when he and his wife moved to Hawaii to save money in moving expenses.

    Having gone through all sorts of lead and NiFe batteries banks over many decades while living off grid, he chose NiFe batteries again. He explains the reasons why in this little video of his:

    This other guy is an engineer who has lived for almost an entire decade with NiFe batteries. He has used both NiFe and NiCd battery banks. In this video, which according to you is looking at life through a rose colored glass (nothing like getting down and dirty) he fixes a bad NiFe battery from China. Obviously he had to replace the electrolyte for it to work:

    If you want really catch my attention, then I would want to see you fixing a lithium battery that went wrong in the garage of your own house. Afterwards, I will start paying a more serious attention to you and your reports.

    I personally wish I had half the ingenuity at solving my energy problems that these two guys show in their videos. For me they are worth more than a laboratory report on battery performances.

    These guys are living this stuff daily, and they and their families share equally in their successes and tribulations, and to me they are a source of inspiration for living and relying on their own and with their own resources.

    So yeah, I will chose an Edison NIFe battery any day over a lead or a lithium battery unless something worthwhile comes along, and so far ‘the proof is on the pudding.’



  36. Cindy Scott says

    I am preparing to sign up for solar, having read Finn’s book. Live in the inner suburbs of Melbourne. Been here for 12 years and can remember one blackout.
    Renovated the house last year, rewired and now have 3 phase power.

    Not looking at getting batteries any time soon, will consider once they are a better deal.

    Should I get a 3 phase inverter in this situation? Planning to instal 20 320Watt panel Sunpower panels with a Fronius 5kW inverter.

    • Ronald Brakels says

      Hi Cindy, Ronald here.

      The system you have planned will work with a single phase inverter. I would usually recommend a three phase inverter because they generally deal better with overvoltage problems caused by the grid, but it’s not essential and if you are on a budget you may decide it is worthwhile to get a lower cost single phase inverter and take the risk of having slightly lower average production than you would get with a three phase inverter.

      If you’re not on a budget, since you have 3 phase power, I suggest getting as large a solar system as will easily fit on your roof. This is because, provided you have the right electricity plan, it is likely to be a good investment.

      Here is a little information on single phase versus 3 phase inverters:

    • Tim Efthymiou says

      Hi Cindy, Make sure your the inverter you choose is a hybrid which will be able to charge any future battery installations. A standard inverter (single or three phase) does not have the capability to charge batteries. Furthermore try and choose one with wi-fi capability which makes it real easy to keep an eye on the performance of your whole system. I have been using a 10.4 k.w. solar system with 3 batteries (totalling 23.5 k.w. battery storage) for the past 3 years. No hick ups and haven’t paid an electricity bill since then. Furthermore, I usually receive a credit in the vicinity of $400 per1/4 during summer and about $190 per 1/4 in winter. Well worth the investment. You do need though, to be on the right plan and fine tune the way you use electricity. For example, if there is rainy days coming up, you could force charge your batteries during off peak rates at night to use the next afternoon during the peak rates. There is a lot you can do to fine tune your system. If you want more information on this, or personal opinion on which battery(ies) to choose, message me and I could give you complete details of how I run my household. Cheers, Tim.

      • Ronald Brakels says

        Well, if Cindy does get batteries in the future she may go for an AC coupled solution such as a Powerwall 2. In this case getting a hybrid inverter would have been an unnecessary expense. For people who aren’t sure about getting batteries I’d say don’t worry about getting a hybrid inverter at the moment. It’s a rapidly changing field and it may not end up being compatible with the battery you want.

        • Tim Efthymiou says

          Hi Cindy and Ronald, Yes, your right Ronald. It is a fast changing field. BUT if Cindy want batteries in the very near future (like in the next 6 months), then she will have to look at different options. I have personally used Tesla products and Lg products (batteries) and the L.g. batteries are much cheaper and in my personal experience are much better option than the overpriced powerwall products. So Cindy, look at the PW2 price installed, and have a look a 3 phase hybrid inverter price, (installed), (which you can hook up pretty much any battery to), don’t forget to compare k.w. storage as well for the batteries, Do the maths and your homework before committing to anything. This is an investment and should be treated as such. Look at a reputable company with good warranty, that has been around for a while. Usually, you get 25 years warranty on the solar panels, 10 years on batteries (sliding performance scale warrantee) and 5 years on the inverter. Cheers for now guys.

      • Andrew Keenan says

        Hi Tim, I’m looking to get Solar installed here in the Adelaide hills we’re on 3 phase. I’m really interested in your set up especially how to charge the batteries on the night tariff. New to this site and not sure how to email you.

        • Tim Efthymiou says

          Hi Andrew, I got your message. The charging of the batteries is done through an lcd screen that is on your inverter (hybrid inverter). It’s very easy to program. Most hybrid inverters will have this feature. Once you enter your inverter password, you go to “force charge” and enter start and finish time of charging. There is a few other options of how many k.w. etc. and different charging programs (like start charging at say 1.00 am and finish at 4 am and then restart charging at 4.30 am and finish at 7 am etc. But you can keep it as simply or as complicated as you like. I’m not sure as to the Tesla pw2 charging procedure as I haven’t got experience with the pw2, but the pw1 is a pain to charge, as I have to ring Solar Edge and tell them to force charge my battery tonight (for eg.) and they will. But this is too much mucking around and never forced charged the Tesla. But the two lg batteries are very user friendly and it takes me 10 seconds to enter a programme to force charge them. Let me know if you have any other questions as I have successfully done away with my electricity bills and have been receiving a credit every 1/4 for the past 2 + years. email me directly so i can get any follow up questions, because most comments on this site end up in my junk mail and I have to search out for them. [email protected] Cheers, Tim.

  37. OZbloke38 says

    Just got a quote after reading this through my builder as I’m getting a 6.6kw solar system for $1990 and for a 3-phase inverter they want an extra $815! Not even close to the $300 quoted here…..

    I know it is a bloody rip off as my parents just got one for $400 and that is more expensive than this site quotes.

  38. Hi guys,
    I’m the process of getting a new solar system for my three phase house. I have been quoted on a single phase inverter for a 6.6KW system (5KW inverter) and also a 8.2KW system (8KW inverter)?
    Not sure whether should ask for a three phase inverter (no plan to have a battery as of now)?
    Also, not sure if an 8KW inverter would be good for an 8.2KW system?

    • Tim Efthymiou says

      Hi Alan, 8.2 k.w. system will be fine with an 8 k.w. inverter (you could go 133% (by memory) higher solar system than the rated inverter), this is because you will never get 8.2 k.w. out of an 8.2 k.w. solar system). At best you will probably get about 6 -6.5 k.w. This is due to the way the cells face, what time of the day, cells facing different directions (north, west) etc. depending on the install. etc. etc.
      if you already have three phase at your house, I would definitely go for the 8.2 k.w. system and split the load to all three phases of the house. If you don’t have three phase at your house, then stick to a single phase with the BIGGEST solar system you could fit on your roof. You will soon see the savings and become addicted and would want to expand, so you might as well fill up your roof now with the biggest system you could afford / fit.
      Lawrence mentioned underneath “what are your motivations for getting a three phase inverter”, well if you already have three phase at your house, then there’s your motivation, since you have it, use it and split the loads, it will be a much more robust system. if you have a three phase at your house and get a single phase inverter, which phase would you connect it to ??? You would have more thinking to do, to figure out which is your biggest load phase and connect it to that one and leave the other two phases as they are.
      I’m speaking from experience and have 3 phase at my house with two separate solar systems and three storage batteries. Cheers, Tim.

    • Ronald Brakels says

      Hello Alan

      I generally recommend getting a 3 phase solar inverter. This is because they generally suffer less output loss due to grid over voltage events. They cost a few hundred dollars more but can pay for themselves if overvoltage events in your area are common.

      I also recommend getting as large a solar system as will reasonably fit on your roof because, unless their are shade issues, the extra amount you need to pay for a larger system is normally a good investment.

      An 8 kilowatt inverter will have no problem with 8.2 kilowatts of panels. With an 8 kilowatt inverter you could have up to 10.66 kilowatts of panels, although that may not fit on your roof. There are 7 kilowatt and they could be used with 8.2 kilowatts of panels, but a 6 kilowatt inverter is just a little too small. Solar panel capacity can be up to one-third greater than inverter capacity.

  39. Lawrence Coomber says

    Hi Alan.

    Have you got any 3 phase loads (circuits) to supply (example 3 phase motors)? If not what factors are motivating your discussion about installing 3 phase PCE?

    Lawrence Coomber

  40. Dominic Wild says

    It looks like in WA we have a 5 kW max. of feed-in for single-phase, or so I am told, however, if it is a three-phase system, I can feed in a max. of 3 x 5 kW, BUT the sales lady then said I lose the feed-in tariff for feeding in more than 5 kW??

    As that company may not be selling 3-phase inverters, this might just be BS. Is she correct for the WA system?

    • Ronald Brakels says

      Unfortunately, yes. In Western Australia they don’t give a feed-in tariff to homes with a total solar inverter capacity of over 5 kilowatts. And — unless they’ve changed the rules — they won’t allow export limiting that will prevent your home from ever exporting more than 5 kilowatts.

  41. Hi, I am weighing the benefits of converting our house (Brisbane inner-north) to 3-phase, at cost of $3,000, in order to have a grid connected 8kW solar inverter and a Tesla Powerwall 2 (has a 5kW inverter built-in from what I understand). And I have some questions about how 3-phase works with a Powerwall 2.

    Originally I got quotes for 10kW panels, 8kW solar inverter, and a Powerwall 2 (intending to use on single phase), but I have been informed Energex wont approve more than a 5kW system on single phase if you also have a Powerwall 2, because the total inverter capacity allowed on single phase is 10kW. (No idea if this is true, just what we have been told).

    One solution presented to us is to upgrade the house to 3-phase so we can get around the Energex limitation. Does anyone have any experience with that?

    Our main reason for getting solar is environmental — to reduce our reliance on the grid, and (however irrational) try to have the actual electric power we use come from solar. Hence the battery – we like the idea of using “our” power at night rather than feeding in solar all day while at work followed by using coal-fired power at night.

    Using the system above as an example: “A single-phase solar inverter and an AC coupled battery. The backup is all on the ‘black’ phase.”. Even after upgrading to 3-phase won’t all the inverter capacity still be on a single phase? (in my case 8kW solar inverter plus 5kW Powerwall 2 inverter). In which case maybe this also wont be allowed by Energex?

    In which case they may want to install a 3-phase inverter. From what I understand the Powerwall 2 will then be just on one of the phases. If that’s the case, am I right in saying the following things are true?

    1) When a blackout occurs, only the appliances on the single phase that is attached to the Powerwall 2 will be kept on? Anything on the other 2 phases will go dead straight away. Is that how 3-phase works with a Powerwall 2?

    2) During a blackout, sunshine will do nothing for us because the 3-phase solar inverter would be unable to be kept on by the Powerwall 2? So we’d have battery power and thats it, even with panels in sunshine.

    3) Only 1/3 of the solar we generate will go to the battery? (probably still enough to fill the battery on an average day in BNE with 8kW inverter).

    4) While the sun is shining we would be best to spread our energy usage over the 3 phases such that none of the phases are using more than 2.6 kW (8kW /3 phases), to minimise the amount of coal fired grid power we use?

    Sorry if this is all obvious, I’m still learning. It was all so simple last week when I thought it would all be on a single phase. Now I am trying to balance which appliances to move onto which phase (e.g. balance those things needed in a blackout and not having too much power on a single phase). The other option being to ignore the environmental aspect and just leave all the power usage on 1 phase, and leaving the other 2 phases as 100% feed-in to grid only.

    Any feedback or thoughts would be appreciated. Thanks.

    • In answering your questions :-

      1) Correct. PW2 can only keep one phase up in a blackout. Even if you have the gateway 2 and multiple PW2 on all phases, blackout protection is only on 1 phase, and only from the PW2 on that phase.

      2). Yes, you are correct. If you have a 3 phase solar grid tied inverter, that will never work in a blackout.

      3) No. When not in blackout, you will be able to use ALL your excess solar on any phase to charge the battery on 1 phase. Technically, it is not really going between phases. But the PW2 will monitor export and import on all phases, and will charge in order to “net the demand out to zero” at the meter. So you will probably be exporting on the 2 solar phases, and importing on the PW2 phase, so from a billing point of view you are able to charge from solar on all phases. I hope that makes sense.

      4) Spreading load across all phases real advantage is more about “reducing voltage rise” which might or might not be a problem in your area, and getting around DNSP rules which limit the amount of solar on a single phase. If you want kill coal, it really does not matter what phase you do that on. Irrespective of phase or time, every kWh you send to the grid, or do not draw from the grid will be a kWh that does not need to be supplied elsewhere, which will likely be doing your own small part to shutting down a power station.

      A few other thoughts :-
      – Make sure you understand the arguments about battery’s actually NOT reducing CO2 emmissions, and if you want to reduce CO2 emmsions, and shut down coal earlier, put as much solar as you can fit. When we have higher penetrations of renewable energy, batteries will help reduce CO2 and shut more fossil fuels plants, but we are a fair way off this. The main reason for this is the round trip efficiency losses that come we batteries, which means it is more efficient to export your solar power to your neighbor, so he does not have to get it from a fossil fuel plant. This avoids typically about 12% efficiency losses that come with a battery.

      – I hope you realise your battery will likely never pay back its investment unless you are in SA and have a massive subsidy which gets the installed price to well less than $5K, and you have the right usage patterns. If anyone tells you you are going to actually save money with a $15k PW2, they don’t know what they are talking about, and educate yourself on solar quotes and other places about this.

      – if you think about the above, the main tangible benefit (besides the warm and fuzzy feelings which I a lot of people including myself have that is not necessarily based in sound logic but non the less can help with a personal battery justification), is for blackout protection. And if so, I recon it will be important to have battery system that can charge from solar when the power is out. If so you do have some options. 1) look beyond a PW2 (though probably expensive but more likely to present a “real” grid independance option by including other things like generator input etc) 2) Get solar installed with 2 or 3 single phase solar inverters (PW will still be able to use solar on all phases to charge as described above). This will allow you to navigate around the issues with 3 phase solar inverter, and still allow solar on the PW2 phase to run in a blackout. Obviously you will need to navigate around DNSP rules, but ideally you maximise your solar on the PW2 phase as that is the only 1 that will work. 3) look at micro inverter solution. This is not without its challenges. But for the latest, you can google for a thread on whirlpool called “Tesla Powerwall battery” and see a post that swainstm did at about 2:20pm. But bottom line is get installer you knows why micros have to shutdown in a phase imbalance and guarantees to install in a way that gets around those issues.

      – if you are doing it to save money, or even for the environment, just put as much solar as you can fit on your roof and the DNSP will allow you to, and ditch the battery which will NOT save you any money. But install in such a way taking advice above so you can later install a battery when battery prices and tariffs make batteries more cost effective. Only caveat if you can install more than 10kW of solar. At least here in NSW, there are multiple providers who will offer “premium” solar FiT. eg you can get FiT of 20c / kWh, which is much better than the usual 8-12.5c offers, and will really help the economics. But these plans are often limited to systems of not more than 10kW. So if you can get one of these offers, or you can only get say 11kW, it might be beneficial for you to stick to 10kW.

      Good luck with your investigations.

      • Further to the above information, suggest you read :-

        Which covers some of the 3 phase options. Really what you are talking about with PW2 and 3 phases is “Configuration #5: 1 single-phase battery inverter with a 3-phase solar inverter and 3 x CTs”

        But note, technically that is with a 3 phase inverter. But in truth if you had this but with multiple single phase inverters, or a micro inverter solution, you could probably navigate around problem that you can’t keep 3 phase solar inverter working in a blackout, and thus the recommendation to avoid the 3 phase solar inverter from me if you can about maximising your flexibility in a blackout.

      • Wow, thanks for the detailed and quick response. I do realise the battery will never come close to paying for itself, and I’ll look further into the options you gave, and that Whirlpool thread.

        To be honest blackout protection is not high on my list – the battery idea was mainly environmental. I assumed no grid power would be used by our house while 1) the panels are producing enough electricity to cover our daytime use, and 2) other times if our usage is less than the 13.5kWh capacity of the PW2 (our usage is well below that now of an evening). I.e. if our usage remains as low as it is now, we would be effectively “off grid” with the battery. Perhaps for single phase that is close to being the case (I think?), but it sounds like with 3-phase we would likely be swapping solar electricity on 2 phases (to the grid) for coal-fired electricity on the battery phase (from the grid) during the day if our household demand on the battery phase exceeds the solar capacity on that phase. Not as “off grid” as I’d hoped.

        I think your Option 2 might get us some of the way towards environmental positivity- keep the house lights and plugs wired to a single phase, which we get a 5kW solar system and PW2 installed on. Then on one (or both) of the other phases get additional single phase systems installed. However the $$$ will start to rise up, what with the costs of getting 3-phase installed and the additional inverters etc. etc.

        Thanks again.

        • Fair enough. I too like the idea of never drawing coal power. That is why I get green power (though technically I don’t think that means I am getting coal power at some stages when it suits coal as I think the green power is an overall thing and not a minute by minute thing). So maybe your battery is a more accurate way of achieving that (though remember there will be days you can’t fill you battery because of not enough solar).

          But I am suspicious that that the coal generators would prefer you to have a battery than not. They make their money at peak times, and by charging your battery at peak times rather than exporting it, there is more money they can make at peak times from your neighbors (though peak times are changing due to solar). Power you use from them at off peak times at night, they don’t really make much money from, and it is more about keeping them going (because they can’t ramp up and down fast). But peak times are changing, and it is probably more about when they can game the market best so it is ever changing so there might be some swings and round abouts here.

          But I can totally understand the warm and fuzzy feeling of reducing your usage of not using power from the grid still dominated by coal. And there is no doubt a battery can help you achieve that. Don’t worry if it is on different phases, as that won’t result in a single extra shovel load of coal going into a coal plant.

  42. Ian Thompson says

    Hi Adam

    My experience with a 3-phase grid-tied 5 kW inverter, is that if 1 phase drops out, the ENTIRE inverter shuts down (I’d think this a reasonable safety response, and doesn’t happen very often).

    But worse, if even 1 phase gets to an excessively high voltage, then ALL of the phase outputs are throttled back (there is no direction to lower voltage phase(s)), and if the voltage is too high, the entire inverter trips out. In my case, the throttling was quite significant (up to 50%).
    Because I have East and West panel strings (no choice), I was finding the East side would cause one of the phases to go high mid-morning (as all the local panels on that phase started generating heavily) and the inverter would be throttled on all phases, the inverter would clip at 5 kW during the middle of the day (quite normal, and reasonable), and another phase would cause the inverter to throttle in mid-afternoon as the West panels in the district generated significant power.
    Had this investigated, and the problem was not in my inverter-to-meter wiring, nor the meter-to-street wiring. Luckily (for me) Synergy were eventually able to “tweek” the sub-station high voltage tappings and the problem has gone away. Until more rooftop PV come online, I’d guess.

    I don’t know of a technical solution to your blackout switch-over, but have heard of automatic change-over/isolation contactors – I’d think one configuration of these could isolate all 3 phase from the grid in the event a phase drop-out should occur, and at the same time connect one of your proposed phases to the Powerwall – it would make sense that this phase carries refridgerators, and any critical light circuits, security, etc. – maybe extend to a GPO of 2 (e.g. let you boil a kettle, run a microwave).

  43. Ian Thompson says

    Hi Adam

    I’d like to add:

    Our metering is NETT – that is, if we are importing 2 kW on one phase, while exporting 1 kW on each of the other phases, then our NETT useage is zero. So the impact on CO2 emissions is no different from a single phase system.

    I do like the concept of 3-phase however, but we are not provided with an option to install a higher capacity system here in WA – for residences, the limit is 5 kW.

    Best regards

  44. David McMahon says

    I have a 10kw system with a 3 phase sunnyboy inverter , but I have single phase power
    The inverter is now only producing about a third of what it should
    Was this a mistake when it was installed 7 yrs ago
    I think I need a new inverter now maybe a single phase Fronius 8.2kw

  45. Hi Finn, I read an article you wrote on a different site about 3 phase trickery, whereby instead of calculating true net export, companies can jig their software so that they calculate separately the cheaper export rate and combining that with the higher grid rate for the non-solar phases.

    As far as you know, might this still be happening?

    My supply is Endeavour, retailer is Origin and I’m in Sydney. Yes, currently
    1phase inverter on a 3 phase supply. Thanks!

    • Ronald Brakels says

      Hi Arthur, Ronald here.

      While this was a concern years ago, fortunately no one appears to be doing it, thank god. Or maybe thank Finn? Perhaps his article scared anyone off from trying it?

  46. Thanks Ronald (and thanks Finn!) if that in fact is the case. Finn your thoughts?

  47. Hi Finn, does anyone make a three phase inverter that is capable of automatically directing all of its output to the phase that has the lowest voltage at any given time?

    If not:
    -Are any companies developing one?
    -Please create a post to announce it if such an inverter does become available!

    • Finn Peacock says

      That is a great idea to help with voltage rise.

    • Ronald Brakels says

      Hi Brendan, Ronald here.

      As far as I know no one makes a 3 phase inverter that specifically exports to the phase with lowest voltage or anyone working on one. I expect it would happen to an extent anyway, but I would need to look into the details of how they work in practice before I could give a firm answer.

  48. To some extent historically AS4777 actually mandates equal current on all phase for 3 phase inverters which would by definition preclude this. HOWEVER, it would appear that the developers of the latest version of AS/NZS 4777.2: 2015 under which all Australian inverters must now comply, optionally envisaged such an implementation. See “Voltage balance modes” in 7.8.1 in

    Though it needs to be pointed out that these modes are “optional” and I suspect anecdotally “Voltage balance modes” might not be widely implemented?? I suspect the implementation would make the inverter more complicated / expensive so might not be seen by inverter manufacturers as high priority (too complicated sell to justify the extra expense to the uneducated consumer)??? After all, DNSPs are supposed to supply voltage within specifications and if they do that us consumers will not care about voltage imbalances between phases, and the extra expense will not be valued.

    Finn, can you guys can provide your knowledge and journalistic powers to finding out if 1) there is any manufacturer who has implemented this mode, 2) to what extent it can completely divert all power to the lowest voltage phase if they are out of balance enough, and 3) what the DNSP position is on this? I assume most would want it implemented if available as I can’t see any downside of anyone and only upside if we ignore any speculated increase in complexity and expense of the inverter.

  49. Hi
    A NZer here and just found this blog as I’ve been considering upgrading my current system. Note my general level of knowledge on solar systems/configurations would be considered low. We in NZ may be a bit different to oz as we don’t have a 3 phase meter that balances the net usage across the phases for billing purposes – each phase is separately metered. I currently have 3 phase to the house with a single phase inverter on one phase (red) and 4 Kw of panels. The red phase has a good proportion of the commonly used circuits with aircon, oven, cooktop and less used circuits on the black phase and hot water only on blue. The blue phase is controlled (ie can be turned off by the network at peak times). I’ve recently been thinking about adding 2-3 kW more and potentially adding a battery perhaps a DIY powerwall from end of life Nissan Leaf batteries. Batteries would only be connected to 1 phase

    From what I understand of the 3 phase inverters this type of setup could be an issue if I changed to a 3 phase inverter. If I understand correctly the solar power is split evely between the 3 phases. While I could even the loads a bit more between the red and black phases I can see I would likely be losing out – eg if say generating 3 kW then 1 kW goes to each phase? If no load currently on that phase then it would export. We currently get a feed in tariff of 8 c /kwH and I pay 18c/kW for the red and black phases and 10-11c/kWh for the blue phase. So wouldn’t I be reducing the amount of charging power to the battery pack with a 3 phase inverter -with battery pack on single phase -and also potentially be exporting when I would otherwise be using the solar power in the single phase setup. i also don’t really want to export on the blue phase at all given the small difference. between what I pay for the power and what I get paid for the feed in.

    I’ve looked at the 3 phase hybrids inverters – Fronius and Solax but these are for high voltage batteries and not 48V systems – and appear limited as to what is compatible. The hybrids from what I’ve read about them appear to support uneven loads across the phases unless I’ve misunderstood (quite likely) But standard 3 phase inverters don’t seem to support this.

    Appears to me I may be best still to stick with a single phase solar inverter and use a separate inverter/charger such as the Victron multiplus II for the battery side of things. BTW I’m not sure that we in NZ have as great an issue with the voltage rise you have in Oz – but could be wrong. Appreciate any thoughts/comments.

    • Ronald Brakels says

      Hi Alan

      I would check that you won’t be required to install a 3 phase import/export meter if you get three phase solar. That just seems simpler than having one export/import meter on each phase. But even with three separate import/export meters if the kilowatt-hour readings are summed and then your bill is calculated it should work out the same as in Australia. But if they work out a mini bill for each phase and then add the dollar amounts together you will be ripped off.

      If you only want 2-3 more kilowatts of panel capacity then I’d suggest just putting a small single phase solar inverter on your black phase. If you were in Australia and interested in do-it-yourself batteries I’d suggest picking up some second hand solar panels for next to nothing and consider making a separate off-grid low voltage DC system. I’m afraid I don’t know how much second panels in NZ are. If you are going to be using a Nissan Leaf battery I recommend being very cautious. Actually, I’d recommend not using one because of the shock and fire risks.

      If you’re the only person in your area with solar no one else on the grid will be causing solar related voltage rise for you. If you haven’t noticed any voltage rise shutdowns on your current inverter then it’s probably not a problem at the moment in your area.

  50. Lawrence Coomber says

    Matthew you have rolled a lot into your post and well done by the way, but the main point in understanding [current I] is that it is always and only ever determined in any circuit by applying ohms law to that circuit and all of the individual sub-circuits within a circuit I = V/R

    Importantly 3 phase power supply will only ever see equal power (V and I) if R (or equivalent circuit R) for the load on each phase is identical (or as near as practical as identical – such as a reactive load like a 3 phase rotating machine); or a fixed (non-thermostat controlled) resistive load R on each of the 3 phases is identical also.

    In practice a 3 phase supply servicing 3 separate single phase sub boards and circuits will never see the same current on each of the phases; and if the current is not the same the power (or electrical work being done) cannot be the same value. The Power formula follows Ohms law as P = V x I Watts.

    Think more about the fundamentals of what you are wanting to grasp Matthew.

    You mention inverters that compensate for varying currents across phase, but this is not the inverters design function. What is possible is to have other PCE circuits outside of the inverter (frequency converter for example such as a VFD) that effectively controls power output through frequency control (i.e. control of the RMS phase voltages of individually single phase sub-circuits through a 3 phase feedback comparator circuit).

    We are accustomed to thinking the inverter should do everything for every situation, but this is a dangerous road to go down and we are seeing everywhere at the moment globally this design and manufacturing strategy is proving problematic.

    Pack to much functionality into an inverter and we often see critical supply being denied to a customer simply because a 2 cent resistor has failed in the inverter communications hardware circuit board, due to a puff of smoke invoking an in box smoke sensor and shutting everything down.

    Denying critical services supply through a simple remote communications component issue in what should be a peripheral to the inverter device, rather than a core functionality element to the inverters main role, is a high price to pay. It may be possible to get away with this in an On Grid scenario, but definitely not in an Off Grid circuits scenario.

    Reduce complex circuits and reduce downtime. It applies to all electronics, and a good example of that is why the isolated iron core transformers are so robust and reliable. They comprise a very low “hardware count”.

    Lawrence Coomber

  51. Lawrence Coomber says

    Alan you need to drill down and crystallise your thoughts and layout what you hope to achieve with the best design possible through the hardware you are contemplating (or already have).

    You need to construct your system design in a simulating software program though and get some genuine calculations out on the table so you can get a real handle on Round Trip Efficiency of your overall AC/DC/AC System Design.

    I recommend System Advisor Model (SAM) software for you to investigate. NREL (National Renewable Energy Laboratory US).

    System Design Commercial Viability is also on the radar; it is often overlooked by people and understandably.

    Also there are many multi-system design techniques used by experienced designers that focus on “consumer loads duty cycle” that provide for having multiple solar/battery generation systems at a premises that have specific duties based on Load Duty Cycle.

    Understand this subject and many doors can be opened and exploited that amount to bottom line savings and efficiencies, that are not well known about across the industry.

    One case in point I can talk about personally; a doctor operating in the suburbs that was contemplating a mains upgrade to accommodate the high demand of a new MRI machine he purchased for his practice.

    After examining the duty cycle of his power intensive machine, it was obvious that he would be better off economically to install a separate single circuit Off Grid (Battery Supply) System independent to his mains system (that had a 5 kW Solar System already) to run the MRI machine independent of the mains.

    Battery charging was accomplished overnight in Off Peak times from the mains.

    This solution saved the doctor over $250,000 up front from an expensive mains upgrade.

    Knowing about and understanding managing Loads Duty Cycle in design, was responsible for this economical system design.

    Lawrence Coomber

  52. I got tired just looking at the number of posts.
    For my part I did put in a 3 phase after a year of putting it to my installer who guaranteed me that a single phase inverter would be fine. It wasn’t….and then the installer began blaming Ausgrid for the over voltage problem.
    My issue is now fixed. The installer replaced the inverter (under threat of Fair Trading and making him refund for the job) and Ausgrid lowered the street voltage by 5V. The system now purrs like a formula 1.
    The take away I have is that any system > 6.6V should automatically require a 3 phase inverter and this will be more relevant as time passes and more and more of us put solar onto their rooves with a coal backed government which continues to refuse to upgrade networks whilst attempting to force coal fired power onto the country.
    I understand that when batteries become affordable I may have an issue but I am hopeful that battery manufacturers will preempt the problem and, like Tesla batteries, provide hardware in the battery pack to accommodate 3 phase inverters. We’ll see in the next few years.

    • Finn Peacock says

      Agreed, it’s not rocket science to AC couple to 3 phase – someone will do it affordably soon – probably Tesla!

      • It might not be rocket science, but 3 phase AC coupling to solar is not easy and trivial either. Especially with solutions that are not integrated (ie battery able to talk to and control the solar inverter directly). Then there are the AS4777 requirements which are mandated for grid stability, but do not take into account battery blackout requirements at all (ie requirement to balance output on all 3 phases and go down on all phases if 1 phase goes out).

        Certainly using frequency shifting to control solar is problematic of 3 phase setups, as you can’t shift frequency of 1 phase without potentially creating problems for 3 phase loads and generators (ie your 3 phase solar) due to the phases becoming out of sync. If you shift frequency on all phases, then you can’t control output on individual phases individually to account for different load and battery charges on the individual phases. Solution to this is to have a single battery bank, and separate inverter/ chargers on each phase to charge/discharge the common battery bank. But this is completely different design to the AC coupled batteries we have today, and would require a redesign of the 3 phase solar inverters that would also break the current AS4777 rules.

        Yes, there are ways around all of these problems with the right design. But basically 3 phase AC coupling batteries and grid tied solar is a whole can of worms. As a result, it is highly unlikely there is going to be a quick fix tweak to existing equipment to get it going. As I see it, before anyone can really start any design work, there really needs to be a significant rewrite of AS4777 to allow the solution AND solar and battery solutions need to designed from the ground up to support it. But I recon that will probably look too hard for a lot of companies, and it probably easier to just go with DC coupling to get around some of these issues. eg Hybrid inverters. But even then, there are downsides. ie somewhat stupid DNSP restrictions and limitations, and of course the advantage of AC coupling is you can add the output of the solar PV inverter and battery inverter together to support even bigger loads which is not the case with a hybrid solution. Also no support of micros which for some people will be important.

        I have my doubts if Tesla likely to be the answer here. 3 years on, and they have still not delivered a relatively simple generator input to the PW2. This is a lot simpler than overcoming all of the challenges of 3 phase AC coupling of solar to what for all intents and purposes is a single phase AC battery. No access to a DC bus to balance change between PW2s on different phases also limits what can be achieved with the current platform. Their software is very basic, and in many cases not functional (ie crappy TOU implementation), so for me it is pretty clear that Tesla’s focus is elsewhere. Also their “philosophy” also seems to be moving in the other direction. ie in the move from PW1 to PW2, clearly they have gone down a more “plug and play” path where their battery inverter can work completely separately from the other devices, which means they can avoid a lot of integration work with 3rd parties. Makes it easy to sell PW2 in a wide range of brown fields sites without having to integrate into everything. But the price to pay for this is server limitations on what you can do (limited 3 phase backup support).

        But lets hope there is more development in this space, because it is a travesty that all these batteries are being installed that will never produce a payback. Blackout protection is something that will be worth real money to people and can help make the justification for some people. So it is just a shame that it is hamstrung in this way.

  53. Steve Hall says

    Thanks for the great stuff Finn

    You said if you found… cause you aint…

    Are you able to comment on Imeon Energy 9.12-3P ?


  54. John Mitchell says

    When I saw this video O assumed that solar was still running on 3 phase through the Backup Gateway 2. Based on what you’re saying Matthew, only the batteries remain operational in this scenario?

    • I have not watched the all the video, but PW2 is pretty limited in its backup capabilities when it come to 3 phase. A few limitations you should be aware of :-
      1. Even if you have PW2 on all 3 phases through a single gateway (ie gateway 2 which supports PW2 on multiple phases), during a blackout, you only have backup of a single phase. Because of this, any PW2 not on that phase will not be doing anything (effectively providing no benefit in a blackout). So the backup in the video would have almost certainly only come from 1 of the PW2. Note : Caveat to the previous comment, is if you installed both PW2 on the 1 phase, then both PW2 could be used in a blackout. However, it is unlikely to be wired that way, because the DNSP rules there would seem to preclude that, and why he had to go out and get 3 phase.

      2. 3 phase solar grid tied inverters must have all 3 phases up to work. So in a blackout, this will not be the case (even though the PW2 will keep 1 phase up), so solar will be offline in a blackout. If you have single phase solar inverter on the same phase as is kept up by the PW2, that that can be kept running in a blackout if wired correctly.

      Curiously, I watched to the point when they did the fail over. What I am curious about, is it appeared to take many seconds to fail over. That appears to be different here, and I think most users can do fail overs without noticing any disruption. Not sure why that is. But suggests the gateway ATS is different between the Uk and Aus?? No idea why that would be. But maybe there are different regulatory requirements there?

  55. Jane Wilson says

    I am clueless about electricity but I should have taken more time to try to find out if it was worth it before having 20 panels installed.
    The house I bought has 3 phase electricity so I was compelled to have a 3 phase inverter. I am one person only in the house.
    My last bill was the largest I have ever received in my life and it was only for 30 days. If anyone has some bright ideas I am all ears !!!!

    • Ronald Brakels says

      Hi Jane

      The first thing I would do is check you are receiving a solar feed-in tariff on your electricity bill. If you are not then either your solar system isn’t working or you need to change to a retail plan that gives you are feed in tariff. The next step would be to check either the screen on your solar inverter or — if it is set up to be monitored online — check it online to make sure it is working and not giving an error message.

      • Jane Wilson says

        Thank you Ronald for replying.

        Yes I am pretty sure there is a feed in tariff because they only give you 7c per kWh for that, whereas they charge you 26c for grid consumption. I am hoping it will improve over the next cycle because the export was only for a month and the billing cycle is two-monthly. I did have a look at the screen on the inverter and it looks as though it’s working (no error message or anything), but honestly what would I know. I hate being so ignorant!!! I need to learn more!

        Thanks again for your input, it’s nice to be heard!

        Cheers, Jane

    • John Mitchell says

      And als you don’t have to have a three phase inverter with a three phase supply. If your installer told you that they were fibbing.

      • Jane Wilson says

        Thank you John for commenting. The installer told me categorically that it was now law (here in Western Australia) that if you have a 3 phase meter you have to have a 3 phase inverter. Wasn’t always that way apparently but it is now, so I was kind of over a barrel.

        Knowing what I now know, I don’t think I would have bothered with solar at all. I believed all the stories people told me about low or no bills, but sadly it looks as though that doesn’t apply to me!

        Thanks again, cheers, Jane

        • John Mitchell says

          Thanks Jane – was not aware of that at all – it may be to try and balance phases better with the increased uptake of solar. I’m thinking with 20 panels you have a roughly 5-6kW system?

          Apart from the front panel do you have access to a monitoring system? Most modern inverters include some kind of monitoring, usually a mobile app. Check with your installer – they should have set it up for you. Without this you’re literally working in the dark. You also need to look carefully at your bill and look for the section with the FiT to see how much energy you actually generated.

          I think you’ll be pleased with your system in the end provided it’s been installed correctly. You probably won’t see the full benefit until next summer when the days get long and sunny. I know in Sydney, February was not a particularly good month for solar this year. Lots of overcast days. My generation was down about 15%. But the good news was – drought ended.

  56. Son Hien Nguyen says

    Please advise which 3-phase inverter 5 kW is better : Fronius or SMA?

  57. Son Hien Nguyen says

    In terms of cost and efficiency for a 3-phase inverter, which one will be a better choice.
    Thanks for the advice.

    • Ronald Brakels says

      Their costs are almost the same. The last time I checked the Fronius was slightly cheaper, although that may have changed. If you are buying rooftop solar then it’s the total cost of the system that will matter, while if you are replacing an inverter differences in supplier markup and installation charge can make one more expensive than the other. The SMA Sunny Tripower 5.0 has a European efficiency of 97.4%. The Fronius Symo 5 kilowatt is 97.3% so they’re almost identical. Generally an SMA it will come with a 5 year warranty while a Fronius will generally come with a five year warranty and an additional 5 year limited warranty that only covers material costs and not transport or labour.

  58. Please advise is it economically worth to spend an extra $300 to get a 3-phase inverter instead of a single phase inverter? Fronius is better than SMA?
    Thanks for your advice.

    • Ronald Brakels says

      Hi Hien

      My advice is to get a 3 phase inverter for 2 main reasons. The first is insurance against against your area having or developing frequent grid overvoltage issues. A three phase inverter is more likely to be able to continue to export electricity for a solar feed-in tariff when this happens than a single phase inverter. It is a gamble, it may never save you a total of $300 but it does represent some additional peace of mind.

      The second reason, which may not be relevant to you, is most homes are limited to a 5 kilowatts of single phase inverter capacity so a 3 phase inverter allows you to install a larger solar system.

      Fronius and SMA inverters are both reliable and well reguarded inverters, so either should be fine. The last time I checked the Fronius was slightly cheaper, although that may have changed. The SMA Sunny Tripower 5.0 has a European efficiency of 97.4%. The Fronius Symo 5 kilowatt is 97.3% so they have almost identical efficiency. Generally an SMA it will come with a 5 year warranty while a Fronius will generally come with a five year warranty and an additional 5 year limited warranty that only covers material costs and not transport or labour.

  59. Finn, your articles are great.
    I have been thinking about solar for my high consumption 3-phase home for years but held back because I am after ” apocalypse proof ” battery backup to all 3 phases as I have some 3 phase motors ( air conditioning unit being one ). Not that I am off beat about the 0.1% chance of grid failure, but want to prevent disappointing consequences of that 0.1% eg. freezer and communications.
    I also regard load splitting as important for the inverter and the grid so agree with you that 3 phase hybrid inverters are the best but not all give the blackout function or couple with a wide range of batteries. This has frustrated me. The manufacturers are begining to offering and recommend these functionalities. More sales of these may improve range and reduce prices resulting in more customer satisfaction and better solar energy local storage and grid distribution. High marketing firms without a charter to inform clients of their best options let many down. I can’t be the only person who feels this way.
    Anyhow, the solution that I currently see for myself is the Goodwe ET 5kW 3-phase hybrid with the Soluna 15kW 3-phase LiMNC battery. I prefer DC coupling for efficiency. Is this possible to cover all those bases and do you have any other recommendations as solutions?

  60. John Mitchell says

    FYI – that battery is not a “3 phase battery” – it’s just a battery. Whether it supports three phases is up to the inverter. And the nominal discharge is only 6kW (with a max of 10kW but that is going to be limited by time), so I’d forget about running multiple heavy loads like air conditioners. The warranty isn’t great either – 5 years plus an optional 5 years whereas most manufacturers are offering 10 years with a min capacity at the end. You’re also limiting yourself to 6.6kW of solar, whereas Ronald has pointed out in many articles more solar is better.

    DC coupling depends on the inverter chosen. I’m not sure if the Goodwe has a DC-DC converter for charging, the standby current is good for a hybrid inverter at <15W. I also don't think the Goodwe's approved for Soluna? I think Pylontech, BYD and LG Chem are the only approved batteries offering CANBUS communication with the battery's onboard BMS.


  61. Noel Sneddon says

    I am purchasing a 13kw solar system and the supplier is offering 2 5kw Inverters as against a 10kw inverter. He claims this is required to balance the system. I have 8 panels on the north
    19 0n the West and another 8 on the west with optimisers.
    I am confused what is he talking about?

    • Tim Efthymiou says

      Hi Noel, a 10 k.w. inverter should be fine, as you will never produce 13 k.w. at any given time. (orientation of panels facing different directions) and a multitude of other factors. Maybe the installer is being extra cautious or wants to give you something you don’t need (for added price). Also this 25kw inverter, could be a left over from another job. I would question him/her about this, and ask as many questions as you can. I have learnt not to trust anyone and I put people through the ringer when buying pretty much anything. I usually come up with the correct answers very quickly, whether their knowledge or experience stacks up.

  62. Lawrence Coomber says


    Whatever way you try to massage the maths; what you have described is a fantasy system overall that does not stack up. If what you say is correct the installer has misinformed you badly.

    Confront him to produce a spreadsheet design for you based on the system configurations he proposes. Then look elsewhere for a professional system designer. The figures do not stack up, and would constitute a non compliant system design.

    Don’t forget to photograph his CEC licence next meeting also. He has some questions that need answering.

    Lawrence Coomber

  63. John Mitchell says

    I think you guys misread 2 x 5kW inverters as a 25kW inverter. My take is maybe because the panels are in 3 different orientations, then one inverter might not have MPPTs to handle the job and you’re going to get a sub optimal result if you hook up two strings facing different direction s to the one MPPT. However if part of the system is using optimisers (confused???) then why wouldn’t you go with one inverter and all optimisers? That part is really strange. Why would you use optimisers or micro inverters for only part of a roof?

  64. Lawrence Coomber says

    No matter what way the maths is manipulated – the proposal by the installer needs explaining if in fact Noel has reported the story accurately:

    Example (unexplainable) designs:-
    A/ 8+8+19 = 35 Modules in Total
    B/ 13000 W divided by 35 Modules = 371.43 W/Module?
    C/ 16 x 371.43 = 5952.86 W (on 5 kW Inverter 1)?
    D/ 19 x 371.43 = 7057.14 W (on 5 kW Inverter 2)?

    Lawrence Coomber

  65. Is it ok to suggest a small petrol generator for blackouts To run fridges/ freezers….small camping gas stove for cooking…torches, candles for lighting
    We only get on average 12 hours of blackouts a year
    I would love battery backup- but too expensive at this time
    All this other stuff is too complicated for my brain
    P.S. l do have a standard 5kw grid connect and love it

    • Ronald Brakels says

      For most Australians looking for something to get through blackouts a small generator is a more cost effective option.

      • Thanks Ron, first I’ve commented….thought I was gonna get lynched….
        Or the electric chair (solar of course)….I’ll leave you blokes to figure out the wiring?

  66. I am interesting making a highbred power back up system for sewer pump stations. Generally the pump stations runs few minutes an hour. but when you use a stand by generators for power failures, you need to use a generator bigger than the pump KW. If you have a battery storage with a small generator, It can provide sufficient kwhr for pumping. This may be coupled with a solar panels instead of generator also depending the cost. Also this has an advantage of running the pump station without the generator for short power outages. can someone enlighten me on this

    • Ronald Brakels says

      That seems to make a lot of sense. These pumps have to deal with huge surges in sewage caused by storms and have to operate if the grid goes down. A large commercial battery could be installed at the site and used to support the grid while also making sure it is fully charged when there is a possibility of a sewage surge. I don’t know anyone working on this.

      • Chandrasiri jayalath says

        Construction of a 4hr overflow storage is a requirement to address power failures. Cost of a 4hr storage is a huge cost and finding a piece of land in a congested suburb is also a problem. battery hybrid system could be a economical system specially for small pump station.

  67. Lawrence Coomber says


    What you are referring to is a: Single or Selected Circuit – Off Grid Power Solution, and you certainly have cost effective reliable and enduring systems options available, that can satisfy the requirements. I have sent you some information by email.

    Lawrence Coomber

  68. Hi Finn and everyone,

    I searched but could not find an answer, hope you could help.
    My house has a 1 phase meter like any normal house in Australia.
    How can I connect a 3-phase solar string inverter to it? That is
    to the main 1-phase circuit breaker panel?
    Thank you very much.

    • If you only have single phase supply, you can’t use a 3 phase solar inverter at all.

      Your only option if you want 3 phase solar (or anything else) is to get your single phase supply upgraded to 3 phase if you want to use a 3 phase inverter.

  69. John Mitchell says

    If you’re in a single phase house you don’t need a three phase inverter. And you can’t use one as it requires some form of three phase supply to work. It makes everything a lot simpler. The recommendation in this article is for three phase homes only. Most solar systems with battery backup are designed around single phase supplies anyway so it makes things simpler and cheaper.

    The only reason some houses have three phase supplies is to handle large loads like air conditioners (which often require a three phase supply) or they have more circuits than is allowed on single phase.

  70. So, my daughter has a 3-phase house in Perth with a Symo 5.0-3 3-phase inverter. Unfortunately she’s finding that her bills don’t seem to be reduced by the solar generation, even though she has very little in the way of heavy consumption equipment (she just has a dishwasher and an electric oven; unlike me, who has the pool pump, electric booster HWS, oven, hotplates etc).

    My first thought was – maybe the inverter is a single phase inverter and she has her kitchen gear on a different phase. However this article settled that issue by asserting that the Symo will generate power on all 3 phases.

    My next thought – maybe the generation (typically 20kwh/day according to Fronius’ SolarWeb app) being spread across each phase, results in insufficient local power on a heavily loaded local phase. For example, assuming the inverter is generating 5kW instantaneously, presumably that equates to only 1.6kW on each phase. That’s barely enough to supply a dishwasher in “dryer” mode. If so, then all other consumption on that phase will have to be drawn from the grid – and perhaps why her high power bills?

    Is that a valid conclusion? If so, then that’s a significant disadvantage of a 3-phase inverter.

    My single phase Fronius Primo generating the same instantaneous 5kW can supply all the gear I might turn on up to that 5kW limit because all my locally-generated power is available to every appliance on my single phase house.

    Would appreciate any reflection on the example given.

    I’m going to visit with a Jaycar power meter to confirm that the fridges and freezers have not gone rogue, but I’m beginning to think the real issue is the way the power is spread over the phases and how the appliances are spread over the phases.


    • Tim Efthymiou says

      Hi Ian, your conclusion is correct. If it’s a relatively new system, she should try to add as many solar cells as practical to add k.w. production. If it’s an oldish system (more than about 4 years old), then there could be a problem with matching up old/new solar cells and might not be financially viable or properly compatible. She also needs to look at the way she uses electricity and what times. My biggest gripe with solar, is that most of the solar production is produced while most people are at work. So she needs to semi-automate her home (for e.g. set a timer for dishwasher to work during the day if she’s at work). Also look at appliances like fridge, air conditioner, clothes dryer etc. these appliances are heavy hitters on chewing up k.w. if they’re very old, consider replacing appliances with invertor technology. Also look at lighting and change to l.e.d.
      You mentioned fridges and freezers. how many does she have ?? If she has more that one fridge/freezer, than consider having only one unit fridge/freezer with invertor technology.
      She also needs to have a look if her inverter is split into the three phases, and see what appliances are hooked up to. It might be worth having the solar system hooked up to one phase, (I think you can go 5 k.w. max per phase), and hooking up (say the oven and fridge to that phase).
      I have heard people saying that even if your solar system is split into three phases and you are using 4k.w. of power and your solar system is producing 1k.w. per phase, that the smart meter takes this into consideration and essentially you are only drawing 1 k.w. from the street. (i’m very sceptical about this, and I’d rather have an appliance draw as much from my produced solar, rather than rely on a smart meter to do the job (which is a bit of an unknown)).
      I have replaced ALL my appliances (over a two year period), also reduced my hot water tank from 400 litres to 120 litres (only 3 people in the house now) I have also added 3 solar batteries to my 10.4. k.w. solar system. I have not paid electricity for about 3 year now. Better still, I get a credit of about $450.00 per 1/4 and I sub sell electricity to a tenant of about $360.00 per 1/4 that’s about $810.00 credit per 1/4 for a 3 person house with ducted air cond. (comes on only during extreme heat), in the bedrooms I have installed small split systems, which are a lot more economical for use on a more regular basis. I’m well on track to have my investment paid off. System has cost me about $30,000. I have worked out payback time of 5.5 to 6 years. This calculation was based on what I was paying and what credits I’m getting.
      So you see, it’s not easy to save electricity, but with a bit of planning, be on the right plan that maximizes your time of use tariff benefits, newer appliances and…. I save the best till last INSTALL SOLAR BATTERIES.
      A lot of people bag me for saying that, and how it doesn’t pay to have solar batteries etc. etc. etc. I want to know, these people that bag about solar batteries, how many have them, I bet 99% don’t have. I have first hand experience and have cracked the code and beat the electricity suppliers at their own game. If you want a more thorough and comprehensive details of my system. let me know. But only if your daughter is willing to make changes, otherwise, I don’t want to waste my time, advising someone and it falls on deaf ears.

    • I can absolutely confirm in Australia, does does not matter what phases your solar and loads are on from a billing prospective, as it will all be netted out at the meter. So if you have 3 phase solar generating 6 kw (2kw on each phase) and you have 6kw of load only on 1 phase, then that will all be netted out and you will not be paying for any import (or getting any export). This is despite the reality that you will be exporting on 2 phases (2kw each) and importing 4kw on the phase with the 6kw load. Again, all netted out at the meter to zero.

      I suspect if it has not gone down much, it is probably that she is not using much power when the solar is running. Also, as you say, definitely review usage and making sure nothing is faulty, but also what uses significant power and trying to run when cheap or it can be offset by solar.

  71. The results of my visit with a power meter…. I reckon there’s close to $3/day potential savings….. or $180 savings per 60 day bill.

    a. Two Windows PCs (Dad’s office desk and lounge TV-spooler) left unnecessarily on, roughly 300 watts, costing about 10c an hour. So $1.60 a day for the 16 hours when there’s no solar power.

    b. Another two computers in the kids’ rooms randomly turned on and off (often left on) roughly another 300 watts. Let’s say they’re left on unecessarily half of the time: $0.80 a day for the 16 hours when there’s no solar power.

    c. Big lounge TV used to display Windows screen unnecessarily when playing music at night. TV uses 220 watts costing 6c/hour. Although peanuts, it contributes.

    d. Fridge set overly low, to 2 degrees – so changed to 5 degrees. Door seal is damaged and not sealing too well – checking cost of seal replacement. Unknown costs.

    e. Dishwasher run boundaries made clearer. To maximise solar use, don’t start before 9am and make sure the cycle finishes before 3:30pm. Unknown costs.

    f. Confirmed that solar inverter is definitely feeding into the grid according to the smart meter – good. Set them up with a routine to record the meter stats at 8am and 5pm daily so we can get some baseline data before they start changing the way they do things. 🙂

  72. Paul Voermans says

    I’d like to know if I can have a 3 phase inverter for just one appliance that requires it but just run single phase to and from the grid?

    • Ronald Brakels says

      Unless you are happy to only use that three phase solar inverter off-grid, I’m afraid that won’t be possible. (If you do want this it would need to be a hybrid 3 phase inverter.) But you can buy equipment that will change single phase power to three phase power for that device.

  73. Lawrence Coomber says

    Paul Voermans

    You have asked a straight forward questions and there is a simple answer:- Yes.

    You can easily and cost effectively integrate a ‘smart controlled system’ that will accomodate (3 phase load circuits) supplied from Solar PV + 3 Ph PCE as well as (single phase load circuits) also supplied from the same Solar PV + 1 Phase On Grid Inverter.

    The key points to consider in system design relate to (the 3 phase equipments daily duty cycle) and ‘smart controls’ that provide for PCE/Inverter isolation compliance; which is easily managed.

    Not all CEC Installers though will be experienced in the PCE and smart controls appropriate for this subject Paul, which will vary according to the 3 phase equipment you want to use, but an RE solutions design engineer can assist you.

    Essentially what I have described is a solution including 2 independent (and controled) systems: 1 x 0n Grid 1 Phase, plus 1 x Off Grid (Single Circuit) 3 Phase at the one premises.

    A very common standard design for factories with 1 or more heavy current 3 phase machines used periodically during normal factory hours.

    Also adding a small capacity battery storage to the Off Grid PCE increases the systems overall efficiency and functionality by managing small night time loads.

    Good luck moving your ideas forward Paul.

    Lawrence Coomber

  74. Paul Voermans says

    Thank you Lawrence,

    For a clear explanation. I have discovered that the device I need three phase for, a kiln, requires 27 kw for up to 11 hours.

    Am I right in believing that a fully off-grid system is now more difficult? I am currently resigned to having to use the grid for when the kiln is firing and use as many 350 watt panels as we can afford and a battery to make up for that draw the rest of the week. We’re not firing more than about 50 times a year so this may work out OK apart from the high start-up cost for 3 phase where we are.

  75. Paul Voermans:

    Based on preliminary info [27 kW furnace x 11 hrs x 50 events) without further qualifications or details – you must have, or are confronted with the dilemma of an enormous annual electricity bill based on kWh, and it is impossible that a furnace of this rating can be used on single phase service supply which normally maxes out at 24 kW of load.

    That being said; there is a simple ground mount solution, to run this furnace from a solar PV array plus 30 kW stand alone PV inverter, and this option is definitely a cost effective one to consider. The key term being ‘cost effective’ though. A useful and enduring system design [especially RE designs] must be determined by the maths stacking up.

    A standalone system this size though would also satisfy your entire premises which will then have two separate systems installed (1) 27 kW Off-Grid, plus (2) whatever your current On-Grid system is. The On-Grid system however will be only used for 100 percent daytime generation output to the Grid for FIT, and also night time loads [all circuits other than the single circuit furnace] which is for daytime Off-Grid system supply only.

    As always the devil is in the detail, and for your situation to be clearly understood, you need to supply more specific info about your electric furnace from the nameplate or technical manual. The 27 kW you mentioned is not sufficient because of how 3 phase heating elements can be configured and controlled; ie. series or parallel plus; how the elements are phase switched which determines the ‘average working current’ per element array. Check your manual or contact your supplier for the answers Paul.

    Elements Volts
    Model – Series/Parallel – Ph – [Ph to Ph] [Ph to N] – AMPS – Watts
    ? ? 3 400 / 230 ? ?

    This is relevant info – particularly the AMPS for solar sizing calculations. Get back with this detailed info and some real calculations can be presented around this project Paul.

    Lawrence Coomber

  76. Michael Matthews says

    My house has 3 phase coming in to the switchboard but only 1 phase is being used. There are 3 fuses labelled “service fuses”, but I can see 2 have wires only going in, where the 3rd has wire in and out. Only 1 main switch.

    I’m in an Endeavour Energy area. Will they allow more than 5kw inverter? I’m getting conflicting advice on this. Thanks

    • Ronald Brakels says

      Hi Michael

      If you have a three phase connection to your switchboard then your installer can put in a three phase solar inverter. It won’t matter if all your loads are on a single phase at the moment. Also, the fact they’re on a single phase won’t make any difference to your grid electricity consumption and the amount of feed-in tariff your receive for sending solar energy into the grid.

      Note it’s still possible some work will need to be done on your switchboard to make it suitable for solar installation.

  77. I LOVE this website & blog. I spent over 4 hours reading through this blog & the other one which talks about the various 3 phase inverter + battery configuration options along with the comments. Thank you Finn, Ronald, Michael, Lawrence and others who have taken valuable time to educate the community.

    I’m in inner Melbourne, looking at installing a 12 – 15 kW PV system (again based on Solarquotes recommendations!) on my roof for a 3-phase grid connected home. I was initially not planning on going down the battery path, but a 0% Finance VPP option from AGL has be compelled to look seriously into the Tesla PW2. I need to lock in the battery option in the next few hours to take advantage of the 0% interest offer.

    For the record in May 2021, I wanted to check if there has been any recent developments/new products/new recommendations for using the PW2 with a 3-phase inverter?

    If I was to summarise here, the options in front of me are:

    1. Option 1 (Recommended) Use a 10kw 3 phase inverter (considering SolarEdge/Fronius). This does NOT provide you with Apocalypse Level Battery Backup as the PW2 will only provide backup power to a single phase during blackout and the inverter WILL NOT charge the battery during the blackout. This seems to have most recommendations with a longer term view on managing stability of PV output across all 3 phases

    2. Multiple Inverter Option 2: Either split solar into 2 independent arrays; or go with seperate ‘single-phase’ inverters for 2 of the phases, and have PW2 on the third phase. This can provide charge the battery during a blackout, but still is not considered Apocalypse Level Battery Backup, as only 1 of the phases will be backed up by PW2? Am I correct in this assumption?

    3. There is mention of “automatic change-over/isolation contactors”, which could theoretically allow a 3-phase inverter to continue to charge the PW2 during blackout, but I can’t seem to find any information on this. Does this magical product exist. If this option was to exist, it would only be a partial Apocalypse Level Battery Backup, as there is no way to charge the PW2 during blackout, correct?

    4. There are no commercially viable ‘AC Coupled’/’DC Coupled’ 3-phase Battery Inverters that exist. Theoritically, if they did, they would offer a full/autonomous Apocalypse Level Battery Backup

    Appreciate any help/comments on above 4 questions/options

    • Not an expert, but for option 2, AFAIK the single-phase solar inverter must be on the same phase as the Tesla PW2 (with a correctly installed n configured Tesla Gateway), to have the ability for that particular phase to island in the event of a grid failure and continue to operate (and charge the PW2).

    • John Mitchell says

      Definitely not an expert but will attempt to answer your questions.
      1. Yes you can do that. I would get your installer to set up all your essential circuits on one phase. Power sockets, lights and perhaps an oven or hotplate if they are electric. If you have an electric storage tank I’d include that as well. The most important things in a blackout are your refrigeration (powerpoints), lights, hot water and cooking. Ducted air is unlikely to run as the power draw is too high for most battery inverters and quite often it’s three phase anway.
      2. You can only really be guided about those things by your installer. What you’re suggesting will work and technically if you do as I suggest above that is Apocalypse protection, as the idea is not to power everything, just the essentials.
      3. An ATS is designed for a generator or a battery inverter combo – so it will switch you off mains if that fails but your inverter will still shut down unless you backfeed it with the battery inverter. The PW2 uses the Tesla Gateway is a “smart” ATS – it tricks the inverter into staying on, but I don’t think it works with 3 phase inverters.

      Finally there are a couple of (expensive) options that could work for a grid tied inverter. SolarEdge make a 3 phase hybrid inverter but it must be coupled with a SolarEdge battery, and I’m not sure about Apocalypse proof.

      The Victron Multiplus II can be paralleled across 3 phases but you need to buy 3 of them. That’s designed to work with a 24V or 48V battery so PW2 would not take advantage of it’s inbuilt smart operation. They are technically hybrid inverters (solar inverter, battery inverter and charger combined) but they have multiple different operating modes and a built in ATS.

      You could also investigate other 3 phase hybrid inverters like SolaX, Growatt etc. and see what they offer in the way of apocalypse protection.

      • Matthew Swainston says

        See my post below this section which was meant to be a reply in this section, but for some reason it put it below.

        But adding to what John says without repeating what I have put below, I suspect the Victron Quattro is the line you would probably be looking at if you wanted the FULL apocolypse battery. I am less familiar with the Multiplus II, but the Quattro brings a few possibly important benefits :-

        1. It is designed with 2 AC inputs. So it is absolutely designed from the ground up for grid input as well as generator input. And if you want the highest level apocolypse battery that will be a doddle to add when you get it. No doubt that would be a way of integrating the Multiplus II with a generator if you really wanted it, but it would require extra bits and I am not sure you would get the same level of integration.

        2. You might need to check whether with the Multiplus you get support for AC coupling of the solar if you want to keep your existing solar inverters (spec sheets does not mention it, but I have seen a clue elsewhere that it might be supported). The Quattro definitely does support AC coupling. AC coupling will be important if you want to support existing grid tied solar inverters. Note : as an aside they also support DC coupling with addition charge controllers, so it is probably one of the only solutions that do both AC and DC coupling of solar that I am aware of besides Selectronic (though there are bound to be others….but most of the commodity hybrid solutions from the guys with the grid tied background I have looked at do not). With AC coupling you will be able to support single phase solar in a blackout. And as John says, with the Multiplus / Quattro if you want 3 phase support, you need to link 3 together (1 on each phase). BUT it is important to note, that I suspect even with this, don’t assume your specific 3 phase grid tied solar will be supported as there are other factors to take into account in the design. You need to speak with a designer would really knows that Victron solution well and can advise you of the limitations (note these people are probably hard to find, but I will give you a tip, if you can’t find someone who can explain what the “Factor 1.0” rule is, you are not yet talking to the right person).

        One of the fundamental issues with any solution with 3 phase and AC coupling of solar will be the fact that just about all AC coupled solar support will come from using frequency shifting to control the grid tied solar (exception being Selectronic solution that has a direct comms link with very specific inverters from companies like Fronius that does give additional options). As soon as you use frequency shifting to control solar, you are presented with only 2 choices when you shift frequency. Choice 1) shift frequency on all 3 phases, or choice 2) shift frequency of different phases as needed. Both have their advantages and disadvantages. I suspect that the quattro probably supports Choice 1) which is good, because if this is the case, then they truly support 3 phase loads in a blackout because all the phases stay in sync. This potentially might mean that your 3 phase solar inverter has a chance of working (if it is supported in the Victron solution). And assuming the 3 Quattros share the 1 battery, there is probably very little downside in this setup. But for battery solutions that go with Choice 2), your 3 phase solar will never be supported, because the phases will quickly fall out of sync, and no 3 phase loads can be supported with this setup. This is probably the reason why the PW2 only supports backups on 1 phase even when you might have PW2 on all phases and why the fundamental architecture of the PW2 is poorly equipped to do anything but very limited 3 phase support and nothing in a blackout..

        I believe John’s statement that the Multiplus is a “hybrid inverter” needs a little correction. Though this is finicky as I will outline below so apologies for John for what is probably nit picking and overall his statement is probably true. Technically I think of a hybrid inverter as one that includes a solar inverter and battery inverter all in the one box. I don’t believe either the Multiplus II or the Quattro for that matter have a solar inverter. The Vitron solution that would no doubt be designed for you would integrate with their MPPT solar charge controllers which are separate components that charge the battery directly, so the solar does not connect directly to the Multiplus or Quattro. But the Victron management box integrates all of this into one solution, so the solution when all put together operates similar to a hybrid inverter solution and so on that level John is correct.

        So if you really want the “ultimate” apocalypse battery, the only solutions I have seen that can deliver this comes from Victron and Selectronic and looks like this :-

        1. Victron / Selectronic battery inverter. If you want 3 phase, you will need 3 of these.

        2. Decent amount of battery and solar to keep any generator requirements to a minimum. Does not matter too much if it is AC or DC coupled and in truth, a bit of both has big advantages.

        3. Generator input, because there will be overcast periods where with would be very expensive and not practical to simply throw more solar and battery at the problem unless you are a very frugal users.

        4. I would make sure I had some DC coupled solar. This will enable the whole setup to auto restart when the sun comes up if the battery runs flat. The problem with AC coupled solar is you create a chicken or the egg problem. AC coupled solar required battery inverter to create the micro grid before the AC coupled solar can restart. But this can’t happen of the battery is flat. MPPT charge controllers to charge the battery will start as soon as the sun hits the panels making it all automatic, and without even needing the generator.

        But again, this is all going to be expensive, and certainly a lot more than whacking a PW2 on existing system. And bang for $ for what you get for a PW2 is going to be hard to beat if you are prepared to trade off some of the “full apocalypse” requirements. And in truth the PW2 solution probably has other advantages as well. For example while the Victron / Selectronic has all the technical stuff to make it great in a VPP, better for the grid etc etc etc, I suspect you might never see it widely deployed in VPPs. I suspect for people putting together VPP solutions it will be easier for them to focus on the commodity battery solutions like the PW2 despite the limitations.

        Like many things it is all a tradeoff directed by your own preference and requirements and if this is making your head spin, go the simple solution.

        • John Mitchell says

          Oops – correct about the Multiplus II. I believe I was thinking of their EasySolar product line.

    • Geoff Miell says

      You state: “I’m in inner Melbourne…”

      I’m try to understand how often you experience blackouts/grid failure and for how long. I wouldn’t have thought it would be a serious problem. Is it more than a few times per year, and for more than a few hours?

      If not, why would you need “Apocalypse Level Battery Backup”? Do you have critical processes that REQUIRE long duration uninterruptable power supply?

      If you are experiencing blackouts/grid failure for more than a few hours (and on more than a few occasions) then I’d suggest you could CONSIDER a switchable backup power system that can keep maintaining overnight your (IMO, in order of priority):
      1. refrigerator(s)/freezer(s);
      2. critical area high-efficiency lighting (e.g. living area, kitchen, bathroom, stairways) and powered doors (e.g. garage doors);
      3. SOME selected general power outlets (GPOs) for low power requirements for appliances like perhaps a radio and/or small TV, internet modem/hub, medical equipment (e.g. blood sugar reader charger, sleep apnea device, air purifier, etc.), and charging portable torches/flashlights, mobile phones, and computers/tablets;
      4. a GPO for one heating appliance for a microwave oven, or electric kettle, or portable single cooktop hob (preferably induction) for defrosting/reheating/cooking;
      5. hot water service (e.g. heat pump);
      6. critical area space heating/cooling (e.g. single-phase split-system reverse-cycle air con);
      7. Clothes washing.

      Most inbuilt electric ovens and cooktop combos & freestanding ranges usually have a very large current draw (32+ amps) and would be expensive to support during a blackout/grid failure.

      Using gas in the home can be unhealthy and more expensive.

      Hot water heat pumps (e.g. a Sanden heat pumps usually draws around 1 kW) can be programmed to run during the day when solar-PV energy is available, to recharge insulated hot water storage tanks.

      If your residence is thermally well insulated then space heating/cooling may only need to run during the day when solar-PV energy is available and the thermal efficiency of the house then holds the heat in during winter overnight, and keeps the heat out in summer.

      I’d suggest the more things you need to support during a blackout/grid failure and the longer you need to keep then running, then the more expensive the solutions will be.

      The real question is whether the benefits of avoiding the inconvenience of low frequency and brief periods of no power events is worth the expense of a backup power system. Only you can answer that for your own needs – others may have a different perspective for their own needs.

      • John Mitchell says

        The voice of reason Geoff. Although these days i think doing all GPOs in a house makes more sense, rather than just a couple. You can then manually limit usage but still have the option of using a device for convenience. Rewiring GPOs back to the switchboard is expensive.

        I would keep all big power draws off the list. Pool pump, 3 phase air conditioners (or any air conditioner that draws more than 5kW) etc.

        • Matthew Swainston says

          Definitely all good points from Geoff. And apocalypse batteries are all a nice feature to have, it is also good to have a think about what value you place on them to justify the expenditure. Because for a typical person, you will probably struggle to get back even 1/3rd of the cost of a $15K PW2 over its lifetime. The most I have aver heard of someone saving per year on “real” savings from a PW2 was about $700 per year. But he had pretty unusual circumstances AND put those together with a custom control system to absolutely milk the last cent of out of an Amber Electricity plan to eak out the last bit of savings from a usage profile that would be close to maximising the benefit from real world solar battery setup. Most peoples real saving would be substantially less than that without attributing all sorts of other things to battery savings like including the solar savings and calling them battery saving, not considering the opportunity cost of lost FiT, usage pattern changes and picking a better retailer which can all be done without a battery. So even spending $15k on PW2, you will probably be needing to justify at least $10K from other benefits like any blackout protection.

          I suspect if you went the Victron solution and wanted all the bells and whistles it will probably be 2 times the outlay and similar saving so you might need to justify $25K which is big money if you live where power is reliable. And of course you are one of these crazy people not afraid of the pending zombie apocalypse that is no doubt going to happen when 12 months ticks over after your covid vaccination when I have heard on good social media authority it is all tipped to go pear shaped (or was that triggered by the 5G radiation to your brain when you ring to tell your friend about the great zombie movie you just saw???).

  78. Matthew Swainston says

    Quick comments :-

    1. As Szern says, for PW2 or any AC coupled solution, you will need a battery on the same phase as the solar to have any chance of solar charging the battery in a blackout.

    2. There is absolutely no way you will get a 3 phase solar grid tied inverter to work in a blackout without battery that does not supply loads to all 3 phases and can effectively replicate the grid on all 3 phases and solve a bunch of other problems that is unlikely to be solved with current regulations. I am not aware of anything that would be able to do this. So the answer to your point 3 question above is there is absolutely no way to keep your 3 phase solar running in a blackout with a PW2 or any other battery for that matter. Even a seperate 3 phase hybrid inverter battery solution is unlikely to support AC coupling of a 3rd party 3 phase solar inverter (happy to be proven wrong if someone can point me at the products that do this).

    3. Don’t get confused with “3 phase” support which can be used in all sorts of different ways by vendors that mean very different things. Something like PW2 does offset power on 3 phase setups (in meter trickery rather than actually generating on 3 phases in the case of a single PW2). They also support multiple PW2 spread across phases, which will give real power on each of the phases. However for blackout support, it is only backup of 1 phase only, even if you have other PW2 on other phases. But in a blackout these will be shutdown and doing nothing. Because you only keep 1 phase up with PW2 and other similar batteries, you have absolutely no chance of keeping a 3 phase solar grid tied inverter up because rules require that power must be balanced across phases. So is a PW2 a 3 phase product??? I would say DEFINITELY not and only a single phase product, but with some extras that allow them some functionality single phase functionality in 3 phase setups.

    4. There is no strict definition of an “apocalypse battery”. I would call it any battery that is able to run for extended periods with no grid because they have the ability to charge themselves from solar with the grid down is the minimum bar to clear (and lots of battery setups fail to clear even this low bar). But this is the lowest bar, and others might want to include other things in their definitions to raise the bar. Eg running all you solar, running all loads and maybe not just particular circuit, generator input etc etc etc. Your definition is up to you.

    5. I personally would not touch a battery that did not have at least some level of reasonable blackout support. And for me personally, I would not touch something that did not have some apocalypse support. The reason is that this is probably the only “logical” (as apposed to emotional or altruistic) reason to get a battery. The main reason a lot of people consider batteries is to save money. HOWEVER, you probably have close to zero chance of ever getting anything you spend on a battery back, never mind actually saving money no matter what the sales person or anyone else says with the cost justification which will be leaving out the real world things that reduce this to a negative return. So at this stage this leaves the only likely tangible benefit of a battery is some blackout protection. So for me this is why it is critical to actually have it. But if you want it because you like the idea, and want to be part of pioneering this technology that might or might not become an important player behind the meter, happy days.

    6. Don’t feel too much pressure about the expiring 0% finance etc etc etc. You will probably find that is just a pressure selling tool and it is likely that or better will be available to you when you are ready.

    7. don’t get too mesmerised with the promises of VPP somehow leading to battery nevarna and being able to pay back a battery. I have not seen one yet that changes the game of not much chance of getting any sort of payback of a battery.

    8. Your question 4, is probably not valid (depending on what you are asking). But refer to comments above. But definitely forget running existing 3 phase solar grid tied inverters in a blackout with any battery solution. But there are batteries that do apparently support 3 phases in a blackout (usually with some pretty significant caveats with for example the more common ones like Fonius). BUT this is not support for AC coupling 3 phase solar inverters, and usually the solar support will have to happen with AC coupling of single phase solar (if in fact AC coupling is supported which is usually NOT the case with hybrid inverters with DC solar). If you want a higher level of apocalypse battery, you will probably want to look at the vendors with a credible level of experience in proper off grid solutions that can bring that to your ongrid setup. Eg, I would look at companies like Victron and Selectronic. They do have solutions that will give you everything for a proper apocalypse battery, and technically do offer this with on grid support. eg DC and AC coupling of solar, support for 3 phase, generator input etc etc (though I am not sure where they are up to with AS4777 certification for all their products for grid connect here). But none of this changes the fact that you will not get your 3 phase grid tied solar working with this solution for very good technical and regulatory reasons (happy for anyone to prove me wrong by pointing me to the magic product). Also note, that I strongly suspect you will need to find that right partner to delivery this. And it will almost certainly NOT be your typical ongrid solar / battery installers. I suspect you will need to be talking to partners that have a proven track record in off grid solutions and a good understanding of the options available. And finding partners that can bridge the murky gaps between ongrid and offgrid (which is effectively what you need in a blackout) in an optimised way with no compromises to either is difficult indeed.

    BUT as you are not saying anything that leads me to believe a HIGH level of apocalypse support is high on your priority list, I suspect some basic apocalypse support will keep things much simpler and cheaper if you value this. So I suspect if you got something like a PW2, put that on a phase with some single phase solar, and put your critical loads on this phase, you have something which will give you some level of apocalypse battery functionality. Keep it simple and reduce the money will will almost certainly lose on any battery setup including this one. Any decent ongrid solar installer will be able to install you something like this.

    Good luck with your deliberations.

  79. Hey Finn,

    Great article and blog, thank you.

    At our small farm we have a 11kw solar array, a 10kw 3ph inverter and a 10kw battery. Our regular consumption is about 60-70kw a day. We seem to get semi regular outages and want to convert the system to be able to run off grid. At this stage we have several backup circuits setup that run at about 1.5kw/h in an outage, the battery does get depleted quite quickly. What do you recommend the best solution to be?

    Would it be possible to install a 5kw single phase inverter next to the 3ph inverter and just have a change over switch from the solar array? Would this then be able to charge the battery and run the back-up circuits or even run all the circuits? Our system is configured essential as you show in Config #8 above.

    Any help would be great, Cheers.

  80. Lawrence Coomber says

    Alex M:-

    If you are considering installing an Off Grid Standalone System at your premises you have plenty of options. Foremost is to simplify your design and what you have described Alex is not an optimum design.

    Create a DC Bus from your PV and you can connect whatever Inverters or PCE you want to this Bus. You are not restricted to one Inverter and can quite easily have a 1 phase and a 3 phase system supplied from a single PV Bus as separate systems [ie. they have their own MCB and load circuits and MEN system]. DC Bus systems are particularly useful for DC Coupled Storage stacks design, and connecting specific load circuits such as Variable Frequency Drives for irrigation and other water pumping circuits, for example.

    There are both single phase and 3 phase inverters approved for solar system + battery DC coupled designs from 20 – 100 kW on the CEC Approved Inverters List at:- (under Product Type – select ‘Standalone PV Inverter’) and there are 48 Inverter models to choose from, that are all eligible for the creation of Government STC’s.

    Standalone PV Inverters are specifically designed for Off Grid Systems that include any combination of multiple DC source inputs including; Solar PV, Wind Turbine; Micro-hydro; Battery Storage for example.

    These specific for purpose design inverters also offer the advantage of a higher DC voltage input range which translates to lower DC operating current; smaller gauge DC input wiring, and extended battery life.

    Three phase is the better option for Off Grid generally as it can be used for any 3 phase equipment at the premises including; variable speed drive irrigation pumps, and equipment using 3 phase motors for example. If however the premises only has single phase loads to service, then a 20 – 30 kW Single Phase Inverter plus a 15 – 25 kW Solar PV Array (+ battery Bank) will provide a reliable and substantial 24/7 power supply.

    Your first task though is to have your premises surveyed by an experienced Off Grid system designer to identify what would be the most efficient and suitable system design to suit your individual circumstances.

    All the best as you move forward with your Off Grid project Alex M.

    Lawrence Coomber

  81. I have a 3 phase and was quoted a single phase inverter. I did ask the question of whether a 3 phase inverter is more appropriate and the response was that the net solar meter, which would also be updated, would distribute the power flow over the phases as required.


    • Ronald Brakels says

      You won’t lose any solar feed-in tariff from having a three-phase inverter. Generally, we recommend getting a three-phase inverter over a single-phase one because they are less likely to be affected by grid overvoltage problems. So, assuming all else is equal, you are better off with a three-phase inverter.

  82. neil newman says

    Hi Finn, thanks for your article really easy to follow.
    One small clarification though.
    We have 3 phase with a single phase inverter. However, what I am lost by is we are generating electricity on one phase and consuming on all three.
    However let’s say I was producing 1500w on phase 1 and consuming 200w on that phase so exporting 1300w… however couldn’t we also be consuming 700w on phase 2 and 900w on phase 3 so pulling down 1600w from the grid, whilst exporting?
    My impression is the power is only consumed on the phase it’s generated on.
    Is that right or wrong?
    Thanks in advance

    • To answer this question and avoid confusion, it is important to distinguish between what happens physically with the electrons in the wires, and what happens in the meter from a billing point of view, because they are quite different.

      From a physical point of view, what you say is 100% correct. From an electron point of view the 3 phases are completely separate and nothing including the meter joins them together to somehow transfer power from 1 phase to the other (more clarification on this point a little later but let’s keep it simple for now as this probably the best way to think of it from a layman’s perspective). Single phase load or generation is only on a single phase, and electrically each phase really operates on its own. So, in your example, you really will be exporting 1300w on phase 1 and importing 700w on phase 2 and 900w on phase 3. And in truth, nothing in the meter or anything else mentioned changes that.

      But how the meter handles and records that is VERY different. The meter will be recording exactly what is listed above, and on lots of meters you can probably press some buttons and see exactly what is listed here if you can see the power draw on each phase, because as said, this is exactly what is really happening. But in Australia our meters are supposed to only bill of for our usage once it is “netted” out. ie it will look and the export or import on each of the phases and add them together, and them only bill for the “net” usage. In your example, at this particular time this will mean that you will be billed for an import of 300w (ie 600w + 900w – 1300w = 300w). Thankfully for your hip pocket, you will NOT be billed for 1600w with what will usually be a miserly FiT which would cost you a lot more.

      In short, people in Australia do not need to worry about whether they have 3 phase or single phase at all from a billing perspective. As it will be the same whether the loads and generation are installed on single phase, or 3 phase as the bill will be the same irrespective of how it is all sliced and diced!!

      Finn’s article is about the benefits of installing solar across 3 phases for voltage rise. He highlights that one way to do this is to use 3 phase solar inverters which will do this and the big benefit of this over a single, single-phase inverter on a 3-phase connection which is all very true. But presenting this way can be misinterpreted as “3 phase inverters good for voltage rise, and single-phase inverters always bad for voltage rise” which is certainly NOT always true. It should be pointed out, you can get all the voltage rise benefits of spreading solar generation across the phases AND an apocalypse AC couple battery with 3 x single phase inverters. So, I suspect the focus should have been on the benefits of spreading solar across the phases, and less focus on 3 phase solar inverters vs single phase solar inverters.

      Most people do not need to read on, because what follows is more likely to confuse the non-lay people and is probably largely irrelevant to most people. What I have put above is 100% true from a bill perspective and this is all the most people need to consider. But I have added for clarification as mentioned above. Some might argue that the statement “From an electron point of view the 3 phases are completely separate” is not 100% correct. In a 3-phase setup, we have the 3 phases that are separate, but where they come together is they all share the same common neutral. This is where 3 phase will start to get complicated and the explanations confuse people but does bring some benefits that make it better than say 3 x independent single phase setup (not that that is how anyone is connected). If we had some theoretical circuit with all of the 3 phases perfectly balanced (eg ideal 3 phase load), all the current on the return neutral circuit will actually balance itself out, and there will be no current returning on the neutral at all!!! This is due to the nature of AC circuits and the fact that the 3 phases 120 degrees out of phase. When you overlay that, the 3 sine waves cancel each other out at all points across the cycle. Again, most people do not need to worry about this or have any understanding of this. But it does bring a whole bunch of benefits for the transmission network. Too complicated to go into here but notice for the low voltage lines that run in the street, and come to 3 phases houses have 4 wires (3 phases + neutral). But the 11KV lines that usually run above the low voltage lines, only have 3 wires. And that is because the neutral is only generated at the transformed and is not needed in the high voltage circuit on the basis that the 3 phases are balanced. But again, this is probably making people’s heads hurt more than it needs to.

      But what is relevant for us solar owners suffering from voltage rise issues, and what Finn alludes to, but does not fully explain is all the reasons behind why getting generation spread across 3 phases helps with voltage rise. Most people understand voltage rise happens whenever current runs in a wire and is proportional to the current in the wire. And this is proportion to the impedance in the wire. Impedance in the wire is mostly a function of its length and size. So, most people are comfortable with the fact that simplistically, if you go from single phase (1 wire) to 3 phase (3 wires), you have 1/3 of the current in each wire, so you significantly reduce the voltage rise (by about 1/3rd). But if you triple the size of the wire in a single phase setup, or spread it over some hypothetical 3 x single phase setup, you would get exactly the same result (because V = IR or voltage = Current x Resistant) and in this case it is coming about by reducing the “R” in ohms law (note in each solution we use about the same about of copper).

      But there is another voltage rise benefit on top of this in our 3 phase setups related to the common neutral. Voltage rise you see in your home is a combination of the voltage rise in the wires coming to your home (active wire) AND the neutral return wire. In both these wires the voltage rise is a product of current x impedance of the wire. In a single-phase setup, the current is the same, and the impedance probably similar so voltage rise is probably about half in each. But in a balanced 3 phase setup there will be no current on the neutral, so no voltage rise attributable to that!!! So big benefit of properly balanced 3 phase setup that comes for free if you can balance the phases!!! In the real world, they are rarely likely to be balanced. But even a partial balance will give you part of the benefit.

      But it should be noted that you DON’T need a 3-phase solar inverter to achieve some of these benefits. As far as I am concerned, all these voltage rise benefits can also be achieved with 3 x single phase inverters balanced across the phases, or in fact a micro inverter solation with the micros balanced across the phases.

      If I have some constructive feedback of this excellent article from Finn, while he recognises the benefits of 3 phase for voltage rise, he fails to recognise that the voltage rise benefits come from balancing the generation across the phases, and NOT from the 3 phase inverter themselves. So buying a 3 phase inverter is not the only way to achieve this! You can also achieve a VERY similar voltage rise result if you had 3 x single phase inverters, evenly spread across the phases. And this 3 x single phase inverter setup would bring the big benefit of being more compatible with the apocalypse AC coupled battery! So, to some extent, some of us might be in the position to have your cake and eat it, which is something that I really like to do if I can. Finn probably left this out, because it was only likely to further confuse what is already a confusing issue for the lay person.

      There are other benefits of the 3 x single phase solution over the 3 phase solution :-
      1. apocalypse battery as previously stated.
      2. probably supports more solar stings if that is useful (eg more orientations and shadings etc).
      3. Arguably more redundancy (1 inverter fails, the other 3 still working). Though this is a double-edged sword, as all other things being equal, you triple your risk of a failure at any point in time.

      Downsides :-
      1. for small systems you might not be able to fit enough panels to drive 3 strings??
      2. 3 single phase inverters, probably more expensive that a 3 phase one, and takes more space and install etc.
      3. DSNPs might not like it as much as there is more risk of the phases being out of balance as they would prefer all solar generation to go down if they lose a phase which will happen with a 3 phase inverter…..but the average user would prefer to keep operating on any phases that are up for the single phase loads/generations.

      But put simply, if you want the benefits of apocalypse batteries and minimise voltage rise, speak to your trusted installer about 3 x single phase inverter or micro inverter solutions.

      • Just wanted to say, it was a lengthy read but well written ?

        Would like to mention that I made sure my house was designed (and installed) with a 3 x single phase solution, with both AC and DC-based “Apocalypse” batteries. Been running it since 2017.
        I have a unique scenario in which the 2 batteries do contend with each other, but it can’t be helped *shrug*
        Not sure if I would have done it any differently knowing what I know now.

      • neil newman says

        Thanks so much to you for laying this all out. Makes complete sense now.
        Thanks and have a good one.

    • Ronald Brakels says

      Just to reinforce what has already been said, if you were producing 1,500 watts on phase 1 and consuming 200 watts on that phase, you would be exporting 1,300 watts on phase one. If you were also consuming 700 watts on phase 2 and 900 watts on phase 3 and not producing any power on them, then that power would come from the grid. The net amount of power your home would be consuming from the grid would be 300 watts. If this went on for one hour then your electricity meter would record your home as having used 0.3 kilowatt-hours over that time, as it only measures net energy in and net energy out.

    • Lawrence Coomber says

      Matthew: – has provided a good explanation on this subject; and thank you for your insights.

      There is an another important electrical principal though not yet canvased regarding domestic 1-3 phase connectivity with the grid, and that is Power Factor. Very technical yes – but essential knowledge for every Solar Power Generation Plant owner [that’s everybody with Solar on their roof] because soon [2023 is my estimate] grid connected customers will be charged a new fee, named something like: VPFS – Variable Power Factor Service Charge]. This PENALTY charge is already levied on Large Scale Commercial Solar Generators; whilst small scale domestic customers have been spared up to now. That will change though and it will sting system owners.

      The power factor of an AC circuit is defined as the ratio of the real power (W) consumed by a circuit to the apparent power (VA) consumed by the same circuit. This therefore gives us: Power Factor = Real Power/Apparent Power: PF = W/VA.

      Then the cosine of the resulting angle between the current and voltage is the power factor. Generally power factor is expressed as a percentage, for example 95%, but can also be expressed as a decimal value, for example 0.95.

      When the power factor equals 1.0 (unity) or 100%, that is when the real power consumed equals the circuits apparent power, the phase angle between the current and the voltage is 0 Deg as: cos-1(1.0) = 0 Deg. When the power factor equals zero (0), the phase angle between the current and the voltage will be 90 Deg as: cos-1(0) = 90 Deg. In this case the actual power consumed by the AC circuit is zero regardless of the circuit current.

      In practical AC circuits, the power factor can be anywhere between 0 and 1.0 depending on the passive components within the connected load. For an inductive-resistive load or circuit (which is most often the case) the power factor will be “lagging”. In a capacitive-resistive circuit the power factor will be “leading”. Then an AC circuit can be defined to have a unity, lagging, or leading power factor.

      A poor power factor with a value towards zero (0) will consume wasted power reducing the efficiency of the circuit, while a circuit or load with a power factor closer to one (1.0) or unity (100%), will be more efficient. This is because a a circuit or load with a low power factor REQUIRES MORE CURRENT FROM THE GRID than the same circuit or load with a power factor closer to 1.0 (unity).

      To summarise the jargon: The MORE EFFICIENT all Domestic Grid Connected Customers Load Circuits are [as determined by a Real Time Power Factor Meter intrinsic with the Metering Hardware] the LESS CURRENT will be drawn from the Grid.

      And Customers pay for CURRENT drawn from the Grid [given a nominal Grid Voltage being maintained] and expressed as POWER.

      Power Factor correction devices are widely used throughout commercial industry to great effect, and domestic customers may also benefit from their use.

      Lawrence Coomber

      • ” soon [2023 is my estimate] grid connected customers will be charged a new fee”

        Hi Lawrence. Out of curiosity, what is your source of information suggesting this might come into effect any time soon?

        Also, I assume none of this has anything to do with 3 phase vs 1 phase as PF would have same impact irrespective of 1 or 3 phases or am I missing something?

        Now I should preface this with a statement, I am not a PF expert (though do have a very good understanding of what it is and what it effects or does not affect and impacts on the grid, wires, transforms and generators). And I suspect from previous posts, it is not unlikely you are more qualified than me in some of these areas.

        Some sort of PF charge for residential customers has been speculated about since Adam was a boy. And I assume the right modern smart meters technically further opens that possibility. But without any inside information or sources, I would speculate I doubt any of this is likely to come into affect for small residential customers because it would be a complete can of worms. And for that reason alone, I doubt it would be anyone’s interest to open that can of worms and try to push it through (least not anyone that is at the mercy of customers with choice, or a voter). If they do, I suspect it would have to come with a long public consultation period and a whole bunch of new standards that would likely take YEARS to put through. There would be MANY meters that would need replacing, and I assume most that would need reprogramming. My guess is all of this means it has a low probability of being implemented any time soon if ever.

        The main problem I see is you would be charging customers for something that on the whole they would have very little understanding of, and even less ability to control without significant expenditure. Added to that, fundamentally existing devices in the home have not been designed to take this into effect at all as near as I can tell. A good example is millions of smoke alarms, LED light globes, all manner of switch mode power supplies to a greater or less extent tend to have less than ideal PF. And in many of these cases, they have absolutely HORRIBLE PF. I think you will fine most smoke alarms probably have PF of considerably less than 0.1. I have a large and very popular AC unit which when idle probably has a similarly bad PF. Etc etc etc.

        Let’s take the millions of smoke alarms out there. I have sometimes wondered why there are not standards to correct this if poor PF is so bad for the grid?? Designing and building slightly more efficient PS would cost money, but I speculate would not be too expensive. My stab in the dark guess is they could build a more efficient PS for these devices for well less than $1. Now it is true that a smoke alarm is only a very small load, and some would argue small enough not to bother with. But when you consider the millions of these devices out there, added together make a much bigger difference. So why has the government mandated a standard for all these tiny cheap crap PS to raise the bar for all of us??? There are only 2 sensible reasons I can think of that they have not done this :-
        1. Governments are fairly incompetent and this is all below their radar (probably true, but in which case it is unlikely there will be much motivation for getting behind starting to charge voters for this), and

        2. I suspect that the “any device with a poor PF is bad” or “any household with a poor PF is bad” mantra is missing 1 very important point. The house is FULL of devices with less than ideal PF. Some of these loads are inductive and have a poor PF one way, but some are capacitive and have a poor PF the other way. But the important point is that these different loads will to some extent cancel each other out. So I suspect the capacitive smoke alarm, will be cancelling out the inductive fridge load to some extent.

        Taking point 2 at the grid scale, I assume it is not unlikely some households when all devices added together will have a capacitive PF, and some will have an inductive PF (though this is speculation I would like to validate somehow). And in truth, this might be different at different times of the day. So if the grid loads are principally inductive as you speculate, you would not what a household that has a capacitive load to “correct” that, otherwise the grid looses a bit of “free” PF correction!!

        I suspect the big commercial power users are changed for PF because at their scale it is economic to encourage them to make improvements at the source and reduce the number of wires, transformers and generators that need to be upgraded to support them if they left that to the generators to correct. My guess is that large industrial loads, and more likely to be predominantly inductive loads, so their size and fact that they all probably swing one way further compounds this and makes it more sensible to encourage fixing at the source. But I am not sure this scales well to households. To me that suggestion sounds like it would be using a sledge hammer to crack a walnut and it is easier and simpler for all concerned to leave the DNSPs and generators to manage that issue in the most economic way possible and at scale. And this is why I doubt residential customers will ever pay a direct PF charge (of course we all do indirectly, it is just all rolled into the existing charges which reflect the cost for the average customer).

        There is one service I can see that residential solar customers could provide in the fullness of time to help the grid manage PF, which I could see happening (and maybe already does to some extent in some places where the DNSP requests a solar inverter profile with a leading or trailing PF). I think it is relatively easy for modern inverter to generate power with different PFs (my solar inverters are all configurable with profiles today for leading or trailing PF). So with the right setting, these could help statically offset the PF in the grid to some extent. So potentially customers who provide requested “non unity” PF to offset the predominant grid PF should be compensated for this, not charged for this. I suspect today, this would be a set and forget, one size fits all for all times approach. But with the right standards and new inverters with the right management interfaces etc, I could not see why the control of this could not be given to the DNSP or whoever to allow them to adjust this over time to meet the grid requirements. And my guess is that some VPP might already be doing a bit of this??? But again, going to this level across the board for all new solar inverters all requires a long lead time of consultation, planning and implementation.

        Again, I have a good understanding of PF and the principles and where it affects the grid and generators. But I would be interested to get more insight into loads and the grid from anyone who has these insights. eg, is it true that the grid is predominantly an inductive load today?? Are modern households predominantly inductive loads, or has the balance swung to capacitive loads with more little capacitive power supplies etc? Are the switch mode PS used in computers, TVs and practically everything else in modern electronics capacitive loads as I suspect, or is even this way more complicated than can be generalised into a single statement??? Even cheap power meters off ebay measure PF. But does anyone know of a meter that gives an idea if the load is leading or trailing?

        I should also give a little clarification to 1 statement in your post above that I fear some people might misinterpret. I am pretty sure the statement “And Customers pay for CURRENT drawn from the Grid [given a nominal Grid Voltage being maintained] and expressed as POWER.” could easily be misinterpreted. For residential customers, we are charged for Power (kWh) and NOT current (Ah). And for this reason, the primary purpose of our meters is to get an accurate reading for kWh. Our meters read power based on actual power based on actual voltages, and not some calculated power based on a nominal voltage. Our bills are impacted by the kW of our appliances, and NOT the current or kVA we draw. How good or bad the PF of the appliance plays no part in what resident customers pay directly. They are not just Ah meters. Otherwise most people would be being significantly overcharged because our voltages averages in the grid are well over the “nominal” voltages. In addition to that, if they were just Ah meters, people would already being charged for kVAh rather than kWh and there would be no reason to talk about a PF charge as everyone would already be being changed for any poor PF.

        Lets not confuse people. All residential customers are charged for today and have to worry about today is the power draw of our appliances (in kW) irrespective of if the PF is 0.01 and using enough current to melt the wires, or it is unit PF. There is no need for most people to worry about the complexities of VA and PF at all today. We are not charged directly for kVA usage or less than perfect PF and we can leave that to the grid to handle. That might or might not change at some stage in the future. But I suspect for the vast majority of people, there is no point in worrying about that because unless I am missing something, there is little they can do to address (unless they want to read the find print on things like smoke alarm boxes and every other appliance they buy to try and find one with a better PF which I suspect would be a complete waste of time).

        • Lawrence Coomber says

          Matthew great comments – thanks again.

          1. You may be correct about PF Charges never finding their way onto a Residential Users account [as is the case with Commercial users right now] but my ”sniff meter” tells me otherwise.

          2. I agree with you: the maths around it are trivial for an individual small scale Solar PV Generator Owner, but collectively [and predicably] the math gets interesting.

          3. I did a an aggregate 5 MW Solar case study in 2020 comparing Inverters with advanced Dynamic Power Factor Correction capability [the Inverter capable of injecting Reactive Power to the grid as necessary] verses standard Inverters which do not have this same capability].

          4. The aggregate savings for the customer collective was $1,095,000.00 per annum.

          5. PF is the biggest deal in the electricity generation field moving forward and there is no subject more important for researchers and design engineers

          6. The results above demonstrate that Inverters with Dynamic Power Factor correction that can manage VAR injection, can provide real financial benefits to customers, and also help Grid stability and integrity.

          7. If you are interested in Phasors; Vectors; Complex Numbers; Addition/Subtraction of Individual Load Vectors to produce a Resultant Vector Matthew, I have developed some Excel and other documents that you might find useful.

          Lawrence Coomber

  83. koen weijand says

    in the german standard all solar inverter are set to a maximum of PF 0.95. I tried to explain this as a solar tax. your 5kW install is only 4.5kW in germany. you can read it already in the datasheets of the inverters, the german version is alwasy less. nice concealed version of a tax, hidden in the standard.

    • At the risk of creating disagreement in an area that is not well understood, I don’t see this as a tax. And thinking about a generator that puts out a PF of 0.95 as an efficiency loss of 5% is NOT the right way to think about PF. If we ignore efficiency losses for simplicity (because the bulk of these apply anyway irrespective of if you are generating 5kW at PF 1 or 0.95), to generate 5kW at PF 0.95 takes the same 5kW of power to generate 5kW with a unity PF!!! Yes….I know that a lot out there will be thinking this is wrong including some well credentialed electrical engineers, but it is true and suggest you keep thinking about it until this point makes sense to you because until you do, you have not really understood what PF really is. But to generate this 5kW PF 0.95 load, you will need to specify an inverter that is capable of meeting both the kW AND kVA specification. To generate 5kW at PF 0.95 the inverter will need to be able to do 5kW and 5.26kVA. It is true that not every 5kW inverter can do 5.26kVA. But every 5.26kW inverter that can generate FP 0.95 should be able to do 5kW at PF 0.95.

      I should also point out that you need to understand the different between kW and kVA. They are directly related by PF, but when reading spec sheets, should not be used interchangeable. 5kW at PF 0.95 is 5 / 0.95 = 5.26kVA. But an inverter in Australia can do 5kW at unity PF, it will be able to do the same in Germany. So I think any difference in the spec sheet if they are giving a lower kW number, it will be because they are going the maximum kW output at PF 0.95 which might be as low as 4.75kW if the inverter does not have any headroom to handle non unity PF. But it should say that in the specification.

      So poor PF is not an efficiency loss in itself. And it does not require more coal to be shoveled into the coal fired power station, or extra panels to cover this (if we ignore some small transmission losses). Poor PF is caused by either induction or capacitance which effectively stores power for 1 part of the cycle, but that same power is returned in another part of the cycle. This of course is happening 50 times a second. But no power is being used up, it is just being stored and returned. So it is a zero sum gain. The reason that poor PF is not ideal in the grid, is there is more current flowing in all the circuits. This means the wires, transformers and generators have to be sized to be able to handle this extra current (5% extra for PF 0.95). There will be slightly more loss in transmission and other components, so there is some efficiency losses associated with poor PF. But it is a LOT less than 5%, and these efficiency losses at nothing to do with the actual PF number as such.

      Ignoring efficiency losses, if you have solar panels that can generate 5kW on the DC side, you should be still be able to export 5kW on the AC side with a FP of 0.95 with the right inverter. If the inverter was a 5kW inverter, but could do 5.3kVA you would be all good to got and would be generating 5kW AC at 0.95PF with your 5kW panels and still be inside of the 5.26kVA specification required to do this. But if you have 5kW of panels, and the inverter can only do 5kVA, you obviously need to step up to the next sized inverter if you want to get the full 5kW that your panels can produce out. So this is NO different to any other solar inverter sizing issue in design. You just need to size the inverter correctly. But even if you have a 5kW inverter that can only do 5kVA with your 5kW of solar panel, you will only be capped at 5kVA which at FP 0.95 is 4.75kW during the short peak of the day when they can actually do 5kW. So sure in this case, at the height of the day you output is capped to 4.75kW the same as if you just purchased a 4.75kW inverter. But it is not wasted and nothing gets hot with this “wasted” power. But most of the day you would not be capacity constrained, and when the panels are producing 4.5kW DC, the inverter would be outputting 4.5kW AC with PF 0.95 no problems at all.

      But all this is confusing for lots of people and the subject is not well understood, even by well qualified people in some cases. This is why I tell people not to worry about PF as mostly it does not affect them. Just make sure you have appropriately qualified professionals to advise you to buy generators, inverters etc to cover the kVA requirements of your loads, or in this case specified PF requirements. I assume solar installers in Germany would understand this well and not see it as a big deal. And it would not be surprising if this was implemented here (ie PF 0.95 from our inverters) if this was through to be the right value to correct PFs in the grid here.

  84. koen weijand says

    the same installation in a country other than germany gets 5% more paid under the same solar conditions.

  85. Hi, quick question.
    If I get a 3 phase Inverter (SYMO) for off-grid only applications, can I run a dedicated circuit for an air conditioner and the other 2 phases for critical loads.
    I believe the 3 phase distributes power evenly across all 3 circuits. What happens when only 1 circuit is operating, I assume all the power is sent to 1 circuit only.
    Also, if I got a Hybrid and AC coupled it to a Victron Multiplus, can I have the best of both worlds and use batteries on the Multiplus to start with (any brand / configuration) and as hybrid batteries get cheaper, add batteries to the Hybrid inverter (limited selection) or will the Hybrid not operate correctly without batteries connected.
    Hope someone can shed some light on my question.


    • John Mitchell says

      The main reason for getting three phase is if you have 3 phase loads, like a 400V air con or well pump. While splitting the circuits across different phases is another application you can achieve the same result with different circuits running off a large capacity single phase.

      Combining batteries with three phase at the moment is difficult without a dedicated 3 phase hybrid inverter (and they generally severely limit your battery choice). To achieve 3 phase with the Multiplus II and have the battery feeding all three phases (which you’d need to do in off grid), you need three identical units linked together and talking to each other. So that becomes a budget decision.

      I had a quick look at the three phase Symo Hybrid inverter (as opposed to the non-hybrid) and it only has 1 MPPT and 1 solar input which means you’re limited to a single solar array. If I were you I’d get a proper solar designer in to design the best system for your needs.

      Perhaps Lawrence Coomber will chime in – he’s very knowledgeable when it comes to off grid design.

      • Hi John, thanks for your advice.
        I realize now that a 3 phase Symo wont work with only 1 Multiplus (single phase).
        I believe the best option is as you mentioned, to run dedicated circuits for each load using single phase from a distribution panel.
        At this stage I am planning on the Fronius Primo 5.0 AC coupled with the Multiplus 2 48v 5000 as I can use multiple battery configurations. I am only installing 2 strings of 3000 watts each and will limit the fronius to 5000 watts.
        I AC coupled a SMA Sunny Boy with a Multiplus back in 2013 and it worked very well.

  86. John Mitchell says

    I still urge you to get expert advice. The Multiplus II features 2 AC inputs so you can run a second inverter into it and switch that second inverter on and off depending on demand, however you might find you are better off getting Victron’s solar chargers instead of a solar inverter. That would have less losses going into the system as you are charging your batteries directly from DC, rather than going DC-AC-DC. So you could pair the Multiplus II with a solar charger and a second Victron inverter that will run off the same battery bank. Or you could even consider the EasySolarII (which has the solar charger built in to the MultiplusII) and a second inverter.

    PS – I am not an expert – this is just knowledge I’ve picked up from looking at other’s off grid designs.

  87. Ann Hefferan says

    Hi Helpful Person

    How can I know whether our 3-phases are balanced? Someone suggested to us that our electricity bill was very high because the phases might not be balanced.

    I asked one of the installers to come back and check but all he said was that they are – but no details. I want to pay the bill but I’d like to be more sure he actually checked and it’s right.

    Also, there are two metres, not three. It must be right, but I don’t know why.


    I’ve learnt enough here to know that a 3 phase inverter is what we should go for with our upgrade. We only have a 6 kw system (and a Tesla Powerwall 2) – we definitely need more panels. I guess that could have been the reason for the big bill – 6 kw is not a big system and we are talking Adelaide Winter bill – yes, I know, its not Tasmania. But, it feels like it to me. We’ve since had insulation installed.

    Are solar installers all adept and knowledgeable about balancing 3 phases? It was an expensive upgrade, so we want to ensure we use it properly. We do have a big house, so 3 phase makes sense.

    • Don’t worry about “balancing across the 3 phases”. It should make no difference to your bill which phase loads and batteries and solar are installed on. In Australia, the import and export should be netted out at the meter irrespective of what each phase is doing. This of course assumes that the solar and PW2 are properly installed. With that configuration, the PW2 should be measuring load across all the phases, and exporting enough on the single phase it is actually connected to try to net usage to zero, to the extent of its capacity.

      But there are other reasons beside “balance” to consider which phase you have solar, PW2 and loads on. It should make NO difference when there is no blackout. But during a blackout, the PW2 can only keep 1 phase up. So most people will want the critical loads installed on the same phase as the PW2 so they work in a blackout. For good blackout protection, you will also want to make sure that the solar inverter is no the same phase as the PW2 (assuming single phase, because 3 phase solar inverters will never work in a blackout). This is so solar can run in a blackout and extend your PW2 run time.

  88. Thank you!

    That’s reassuring and makes sense.

    However, could you please clarify what you mean by “(assuming single phase, because 3 phase solar inverters will never work in a blackout). This is so solar can run in a blackout and extend your PW2 run time.”?

    Do you mean don’t go with a 3 phase inverter?


    • If you want the ‘Apocalypse Proof Battery Backup’, then you should avoid using a 3 phase solar inverter with a PW2 or any other AC coupled battery for that matter. The problem with a 3 phase solar inverter, is it will have to shutdown in a blackout, because a PW2 is only on a single phase.

      So if an ‘Apocalypse Proof Battery Backup’ is something you want, then you will want to stick to single phase solar inverters.

      If I was getting an expensive PW2, I would be keen to make sure it provides an ‘Apocalypse Proof Battery Backup’, because with the poor economics of batteries, it is 1 of the real benefits you will get from the PW2.

  89. Hi Matthew

    Thanks again.

    As far as I know, our local grid voltage is stable. So, I was going to go with the advice from Finn Peacock and opt for stable solar generation. But, I will check this out further.

    Thanks to this site, to your help and to Finn, I have some important information that I have an understanding about! I don’t feel like I”m working in the dark!


    But all these options are very expensive. So if you are choosing between a three-phase solar inverter and a single-phase solar inverter/microinverters the question you have to ask your self is:
    What’s more important to you? Apocalypse Proof Backup™ or stable solar generation?
    In my humble opinion it is better to have a system that operates well 99.9% of the time (when the grid is available) over one that operates really well 0.1% of the time (when the grid is down).
    But perhaps your grid electricity goes down much more than that and getting through long outages is your priority. In that case you may want to install a single-phase solar inverter on your 3-phase supply. Just make sure that your installer checks your local grid voltage and voltage rise before you get solar installed. And hope that your local grid voltage stays low in the future.
    You could also install a three-phase hybrid inverter instead of a three-phase solar inverter. But bear in mind that any future battery must be compatible with that inverter – often that is only 2 or 3 battery models and they may be obsolete by the time you decide to buy them.
    So choose wisely three-phase dweller. And do the right thing based on your local grid voltage, your local grid reliability and above-all your zombie tolerance.

  90. John Clarke says

    I have 3 Phase connected to my Property
    1 Phase supplies the house
    1 supplies the annex
    3 Phases supply the barn,

    My question is, will a 3 Phase invertor be suitable due to the unbalanced Load, will my solar array be used efficiently or does the invertor supply based on the lowest phase consumption?

    If the answer is yes then I’m probably better of with single phase invertors connected to the phases with the greatest consumption.

  91. Jeremy Keen says

    Seeking some advice on a system that best utilises the 3-phase power that is connected to my home (for controlled load in-slab heating) to maximise the feed-in tariff’s understanding that the most my provider (Essential Energy – NSW) will allow is 5kw per phase.

    I have basically been offered 2 systems;

    10kw of panels with one 3-phase 8kw inverter (older model I think – Sungrow Power SG8.0RT). No consumption monitoring $10,000 (add $850 for monitoring)
    13kw of panels with two single-phase 5kw inverters (newer/current model Sungrow SG5K-D Premium) $15,500 (no monitoring)

    I presume that both systems will output similar power to the grid, dictated by what the panels are generating? i.e. if the panels are generating 8kw and the house is consuming 2kw, then 6kw will be exported to the grid. I think from reading that this export would be balanced across the phases by a 3-phase inverter, but not by 2 x single-phase inverters?

    The cost of a 3-phase consumption meter at $850 seems high – does this sound correct? Also for the 2 x single-phase system – will I need 2 consumption monitors, or just one….and what would be a reasonable cost for this?

    At this stage I’m not considering a battery system but will either of these lend themselves to be better/worse if I do decide to add batteries later.

    On paper the 13kw panels/10kw inverter (@2 x 5kw) system will produce more power over the year – but it’s also 50% more expensive. I’m not too fused to pay the extra if it gives me a better system in terms of flexibility, and feed in tariff returns over the long run.

    More than happy to take comments, suggestions or recommendations about these 2 options (or any other design ideas).

    Many thanks advance,

    • Ronald Brakels says

      Hi Jeremy

      Both systems should be able to export all the surplus power they produce to the grid. The three phase inverter will distribute it over three phases while the each 5 kilowatt inverter will send it down the phase it’s attached to. Three phase inverters are better at avoiding grid over voltage issues, so if you know grid over voltage is a problem in your area that’s an advantage for the 3 phase inverter.

      The 13 kilowatt system is 30% larger but costs 55% more. I recommend getting larger solar systems so will be ready for if and when you decide to get a home battery or an electric car, but only you can decide if it’s worth it. I’d suggest asking the installer offering the 10 kilowatt system if they can offer you something larger.

      PS: At $850 monitoring isn’t cheap. Whether or not it is worthwhile will depend on your personal inclination. Some people love being able to monitor the output of their system and maximize their self-consumption, while others have little interest in tracking their consumption.

  92. Ranjan Agarwal says


    Recently bought a double storey house in ACT, which has 3 phase power supply.

    Main power consuming devices I think are fridge, air-conditioning and car.

    I have just got a quote for 12.865 kW solar power system with SolarEdge optimiser in each panel, Tesla 2 battery and one single phase SolarEdge inverter. The installer does not have the three phase inverter in stock and not sure when it will be available.

    Quote from other places are considerably higher than this installer.

    You have already mentioned that 3 phase inverter is recommended.

    Is it worth waiting for the installer to get the stock for 3 phase inverter or should I go ahead with single phase inverter?

    I am told that with the single phase inverter, there is restriction around how much electricity it can push to the grid.

    Any advice will be be greatly appreciated.

    • Ronald Brakels says

      Hello Ranjan

      If you get a 10 kilowatt single phase inverter in the ACT it will be export limited to 5 kilowatts. This means it will never send more than 5 kilowatts of power into the grid for a feed-in tariff, even if the solar system is capable of supplying more. This isn’t a huge drawback if you have an electric hot water system and or other devices on during the middle of the day to consume solar electricity, but since you have 3 phase power at your home and the system you are planning to install is large, I would definitely want a 3 phase inverter in your situation.

      An installer who is cheaper than the competition is great, but only good if they do good quality work. You can get an idea of this by looking at their online reviews. If people say they have a problem, check to see if it was fixed in a timely fashion to their satisfaction. If you check them in our reviews, you can click on “See Australia-Wide Ranking” to see how they compare to other installers. If you get a quote through us, we will only refer installers who do good quality work and we back it up with our “Good Installer Guarantee”.

    • Ronald Brakels says

      Hi Ranjan

      I received your last comment, but I haven’t made it visible in case you don’t want people to see your address. The easiest way to get quotes through us is to go here…

      …and then enter your postcode and then answer the questions that come up as best you can. If you want a lower-cost system, say you want a budget system when that option comes up. Even if you ask for a budget system the installers we refer you to will supply one that is reliable and well installed. It will also be covered by our Good Installer Guarantee:

      I’ll also send you an email. Hope your future is sunny.

  93. What options do I have for installing a battery when my solar system is mounted on my shed which is about 30m away from the house main switch (heritage area visibility requirements).

    I could supply the shed battery power but the house will be isolated by the Fronius Symo Inverter (5kW per phase system). Wife and child not happy and me cruising along doesn’t seem quite fair.

    Is there no smart phase fail relay that could be installed at the main switch…..?

    Thank you.

  94. Peter Olsen says

    I cannot find a detailed explanation anywhere of how a 3-phase inverter works with respect to distributing the solar power across the 3 phases. Is it hard-wired, a third to each, or can the inverter increase the power to one phase if it is drawing more than one third of the solar capacity?

    Say I have a 10kw system and one circuit in the house is drawing 7kw and the remainder 0. (I am wanting to connect the HWS to solar which will be an immediate 3.6kw)

    Can the inverter (eg. Sungrow SG10.0RT) supply the full 7kw to that circuit, or can it only supply a third of the total solar supply (3.3kw), meaning there will be an import of 3.7kw from the grid.

    If that is the case, will I be charged grid rates for the imported power (32c) while only receiving the feed-in tariff for the exported power (7c), which would seem to reduce the value of a 3-phase inverter, or is there a net usage calculation such that I would not be charged anything extra during that period?

    • Finn Peacock says
      • Peter Olsen says

        Thanks for that. That answers the financial side when using a single phase inverter on a 3-phase supply. I am talking about using a 3-phase inverter on a 3-phase supply. I am trying to determine how it actually splits the solar power between the phases (ie. hence between the circuits in the house). If my assumption above was correct, that it is hardwired, then I guess the answer re charging would be the same as a single phase inverter.

        • Matthew says

          The link Finn has posted really answers your question for 3-phase inverter on a 3 phase supply and it is exactly the same from a financial point of view. ie all that matters is the net power usage across the 3 phases. eg if you are exporting 2kW for an hour on 1 phase and importing 1kW on the other 2 phases, that will net out to 0kW and you will not be charged anything, and won’t get paid any solar FiT, because it all gets netted out.

          From a physical point of view, a 3 phase inverter must spread any output evenly across all 3 phases. So in you hypothetical situation, you will be importing on 1 phase and exporting on 2 phases, even though you are generation more than you are using. But again, that will all be netted out at the meter, and from a financial point of view you would be net exporting and being paid you solar FiT and no import at that time.

          In fact one of the downsides of a 3 phase inverter, is if you loose a phase, the 3 phase inverter must trip off. And for me, that is one of the big downsides of a 3 phase solar inverter and why I would not buy one. If your grid is reliable, then this is not something you need to consider. However, if the grid is less than reliable and/or you want an battery that will run and support solar during a blackout now or in the future, you might want to avoid the 3 solar inverter now. The issue is that a lot of the battery solutions (eg Tesla PW2) only operate a single phase during a blackout. Because of this, the 3 phase inverter can’t run in a blackout. This is why I would prefer single phase inverters in this situation. In fact if you have 3 single phase inverters spread across the phases, you will get most of the benefit Finn talks about with a 3 phase inverter. Yes, if you have a PW2 backup in a blackout, of course the 2 single phase inverters on the non backed up phases will not work, but at least you will get output from the single phase inverter on the backed up phase.

          • John Mitchell says

            I think the question Peter’s asking is slightly different. He’s asking whether 3 phase solar inverters can output unbalanced power across the phases. ie – if house demand on one phase is 6kW and the other two phases 0kW can a 6kW 3 phase inverter output 6kW on that single phase? The answer is – it depends on the 3 phase inverter. Some 3 phase inverters can only output equal power to all phases and some can do various amounts of unbalanced loads up to 100% of their rated capacity.

            This becomes important in an off-grid or grid down situation where the net metering is irrelevant. Example: you have a 7kW car charger on one phase. Can your 12kW 3 phase inverter send 7kW to that phase or only 4kW per phase?

  95. Peter Olsen says

    That still doesn’t explain how the 3-phase inverter spreads the power which is what I am wanting to understand.

  96. Peter Olsen says

    Thanks for the detailed response. I guess it all comes down to cost. Anyone who buys a battery at present is doing so for reasons other than financial ones because they simply do not pay for themselves yet. Ditto for installing 3 x single phase inverters. By the time batteries are an affordable solution those inverters will be close to end of life so I might as well save the extra cost for now and wait until the industry matures.

    After 25 years or so of solar installations it is ridiculous that most sensibly priced inverters still cannot perform basic tasks that most people would assume they could, such as working in a blackout (a simple contactor will keep the linesmen safe) or powering a HWS intelligently.

    I have survived for over 60 years without any power backup in spite of many blackouts over the years. I now have a 3kW petrol generator that I bought for $200 for emergencies – less than the cost of a freezer full of meat, which is what I bought it for. It will outperform any $10,000 battery every day of the week. Totally automatic too for when I am away. (Burglar alarm msgs me. I ring neighbour and ask him to pop in and pull the starter cord and plug the fridge into backup generator-connected power point. A pity the current generation has forgotten how to be good neighbours.)

  97. I have an existing 5kw single phase inverter north facing panels NSW, on my 3 phase supply.

    im going to add another 5kw system with 50% east 50% west panels im torn if it should be 3 phase (recommended) or another single phase ?

    in my mind the new system will not benefit a lot from the 3 phase as it will have a lower outputs at peak generation times, i think upgrading my exsisting inverter or swapping the inverter locations would in my mind make sense but due to different installers could be a warranty issue.

    my thought is too go with the 3 phase and monitor

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