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 founder of My last "real job" was working for the CSIRO in their renewable energy division.


  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.

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

    That should be … charge your battery…

    Mine can, being off-grid 🙂

    • 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.

  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?

    • 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

      • 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

    • 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.

    • 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.

    • 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.

      • 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!

    • 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.

    • 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. 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?

    • Ronald Brakels says

      Both are considered reliable good quality inverters and both should be good choices.

  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. 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. 🙂

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