Don’t Add Batteries To A 3-Phase Home Before Reading This

3-phase homes and solar battery systems

If you buy the wrong battery system for your three-phase home your electricity bill will not go down nearly as much as you expect. And with the economic return of battery systems being pretty marginal in even the best case scenario, it is super important that your battery gives you the best returns possible.

The bad news is: The wrong (or misconfigured) battery system on a three-phase home will only reduce grid electricity use on the battery’s phase. It is therefore essential that you buy a battery system that is capable of offsetting your grid electricity consumption charges on all three-phases.

The good news is: Most battery systems can do this. You just need to check that the one you buy works optimally with your three-phase supply. The difference between a 3 phase battery system that reduces your bill on all 3 phases and one that doesn’t is often 2 current transformers (CTs). They cost about $30 each.

This post will help you buy a solar battery system that plays nice with your three-phase home.

Warning: Some salespeople may look you in the eye and tell you that the battery system will work just fine on your three-phase supply. But you need to dig deeper. You need to make sure that the battery will work optimally on your three-phase supply. Here’s what you need to know.

What is 3-phase?

Three-phase is a type of grid connection. It describes how your home is physically connected to the grid. All grid connected homes in Australia are either:

  • single-phase
  • two-phase, or
  • three-phase

Single-phase: Most Australian homes have ‘single-phase’ electricity. This means that they have one live wire to their home carrying all their electricity. If you have single-phase, you can ignore this post and carry on with your day.

Two-phase: Two-phase supplies are rare, but some people have them. Two-phase means there are two live wires going into your home. If you have two-phase – you need to read this post as 2-phase battery systems have similar issues to 3-phase battery systems.

Three-phase: As people get bigger homes and more powerful appliances, such as large air conditioners and pool heaters, they may need more power than can flow down a single wire. For this reason, more and more homes are getting ‘three-phase’ connections. three-phase means that you get three live (or active) wires instead of one. It follows that you can have three times the power coming into your home. If you have three-phase power, the phases are red, white1 and blue. Your single-phase appliances run off one of those phases. Any large, three-phase appliances connect into all three-phases. As electric cars become common, more people will start to upgrade to three-phase so they can charge the car more quickly.

There are a gazillion configurations to choose from when installing batteries on three-phase

When I first sat down to write this, I thought I’d quickly draw up the possible configurations available. Then it dawned on me that there are about a gazillion. I present 16 different configurations here with their pros and cons.

Don’t worry about understanding every single configuration. But I hope the following list makes you appreciate that it is really important that your solar installer understands what you need in terms of self consumption and backup from your battery and configures your system to suit. I am getting more and more cries for help from people who have dropped tens of thousands on three-phase battery systems that are not giving them the savings or backup that they expected.

Tip: If you are buying a three-phase battery system, ask your installer/salesperson which configuration they’ve gone for, then make sure it has the features you expect.

Tesla tip: Even if you are simply getting a Tesla Powerwall 2 on your three-phase home, make sure that you are getting 3 consumption CTs and your backup circuits will all be on the Powerwall’s phase.

Definition: A ‘consumption CT’ is a little power meter (Current Transformer) that measures your grid imports and exports.

So here are 16 of the possible configurations for a three-phase solar power and battery set up2. If you are buying a system from scratch it could be any of these. If you are retrofitting a battery and want to keep your existing inverter, then you will have a much more limited choice.

Don’t fancy plowing through 16 schematics? I don’t blame you! Go straight to the summary here.

Configuration #1: three-phase hybrid inverter

three-phase hybrid inverter + battery system

A hybrid inverter is a single device that you directly connect both your battery and solar panels into.

A 3-phase hybrid inverter will convert the DC power output of both your solar panels and your battery to 3-phase AC power.

The three-phase hybrid inverter will monitor your solar electricity production and household consumption across all three-phases using little meters called Current Transformers (CTs), which are the green things on the diagram. It will use this information to know when and how much to discharge your battery so that you always use battery power instead of grid electricity imports wherever possible. It does this by instructing the battery to push out just enough power to offset the grid imports in real time.


  • A 3-phase hybrid inverter balances your phases (which helps grid stability)
  • It minimises voltage rises to the grid (because any load is shared over 3 wires).
  • By default, the battery reduces your consumption across all three-phases, optimising your savings.
  • A relatively simple, installation.
  • If the inverter has a backup feature and enough power, it can back up every phase in the house.



Configuration #2: 1 single-phase hybrid inverter with 1 consumption CT

1 single-phase hybrid inverter with 1 consumption CT + battery system

A single-phase hybrid inverter will convert the DC power output of both your solar panels and your battery to single-phase AC power.

In this configuration, the single-phase hybrid inverter will monitor your solar power production and household electricity consumption across only the phase it is connected to. This means you will only get the benefits of solar energy consumption on that phase.

If the inverter features backup, then you can only back up the connected phase.


  • A relatively simple, installation.
  • Cheaper than a three-phase hybrid inverter.


  • A 1-phase hybrid inverter does not balance your phases, so you are often limited to 5kW of exports by your DNSP.
  • All the load is going down a single-phase, sometimes causing voltage rise issues when exporting. This can trip or limit your inverter operation.
  • The battery only reduces your consumption across one phase, reducing your electricity bill savings.
  • Can’t be done for AC coupled systems like the Tesla Powerwall 2 or Enphase batteries. This is for DC coupled batteries only. And the batteries must be compatible with the specific inverter model.


Configuration #3: 1 single-phase hybrid inverter with 3 x consumption CTs

1 single-phase hybrid inverter with 3 x consumption CTs and battery

Some single-phase hybrid inverters allow you to connect 3 CTs, one for each phase. They can then export enough on the connected phase to offset grid imports across all three-phases. When this battery power gets to the 3-phase meter, the meter subtracts the power being exported on the battery phase from the power being imported on the other 2 phases to give you zero net imports as far as your billing is concerned. Nice.

Single-phase hybrid inverters controlled by a Reposit controller can do this.


Configuration #4: 1 single-phase battery inverter with a 3-phase solar inverter and 1 consumption CT

1 single-phase battery inverter with a 3-phase solar inverter and 1 consumption CT

If you want to retrofit a battery to an existing three-phase solar power system, or keep your battery and solar systems on separate inverters, then you can use a battery inverter that ‘AC couples’ into your switchboard. That simply means that it converts the DC from the battery into 230V AC that is wired directly into your switchboard.

If the system only has one CT, then the battery can only offset your consumption on one phase.


  • It can be retrofitted to existing solar systems without touching the solar installation.
  • A single-phase battery inverter is cheaper than a 3-phase one.
  • Your battery system and solar power system are separate making maintenance, warranty claims and upgrading simpler.
  • A three-phase solar inverter allows you to fit more solar panels now or in the future (3 times more funnily enough)
  • A three-phase solar inverter pushes the grid voltage up less when you are exporting solar electricity, reducing the chance it tripping or derating due to grid voltage rises.


  • Your battery savings will only be on one phase.
  • You can only back up the phase your battery is connected to.
  • It is not possible to charge the battery from the solar panels during a grid-outage because the 3-phase solar inverter needs to see 230V on all phases to operate. The battery inverter can only produce 230V on one phase.
  • A three-phase solar inverter costs more than a single-phase one.

Configuration #5: 1 single-phase battery inverter with a 3-phase solar inverter and 3 x CTs

1 single-phase battery inverter with a 3-phase solar inverter and 3 x CTs


This is the same as configuration #4 but the battery inverter allows you to connect 3 CTs, one for each phase. This allows you to have the benefits of battery energy self consumption across all three-phases.

If you have a choice, always choose this over the previous configuration as it will reduce your bills more, assuming you have any appliances connected to the other 2 phases.


Configuration #6: 1 single-phase battery inverter with a single-phase solar inverter and 1 consumption CT

1 single-phase battery inverter with a single-phase solar inverter and 1 consumption CT

This is the same as configuration 4, but the solar uses a single-phase inverter.

Advantages over configuration #4:

  • If the battery inverter offers the feature, it is possible to charge the battery from the solar panels during a grid-outage. The Powerwall 2 does this with compatible units for example.

Disadvantages over configuration #4:

  • A single-phase solar inverter pushes the grid voltage up more than a 3-phase one when you are exporting solar energy, increasing the chance of voltage rise issues.

Configuration #7: 1 single-phase battery inverter with a single-phase solar inverter and 3 x consumption CTs

1 single-phase battery inverter with a single-phase solar inverter and 3 x consumption CTs

The same as the previous configuration (#6) except the battery inverter allows 3 CTs, so you can benefit from battery self consumption across all three-phases.

The Powerwall 2 offers this feature and is simply a battery plus battery inverter in one sleek box. It can be used with a single-phase solar inverter as shown, or a three-phase solar inverter. But with a three-phase solar inverter your battery can’t charge from your solar during grid outages.

Tesla Powerwall 2 battery configuration - simplified diagram


Configuration #8: Three-phase battery inverter with a three-phase solar inverter


1 single-phase battery inverter with a three-phase solar inverter

Here the battery inverter is a three-phase device, which means that it converts the DC input into 3 AC outputs.


  • A three-phase battery inverter pushes the grid voltage up less when you are exporting battery power, reducing the chance of the battery inverter tripping or derating due to grid voltage rises. This is only an advantage if you plan to export lots of battery power to take advantage of high feed-in-tariffs or grid support functions like Reposit.
  • Battery savings are across all phases.
  • Backup is across all phases.


  • A three-phase battery inverter is more expensive than a single-phase one.

Configuration #9: Three-phase battery inverter with a single-phase solar inverterThree-phase battery inverter with a single-phase solar inverter

This is simply the previous configuration with a single-phase solar inverter to show you can mix a 3 phase battery inverter and single phase unit if you need to.


Configuration #10: Three batteries, three battery inverters and an inverter with a three-phase solar inverter

Three batteries, three battery inverters and a inverter with a three-phase solar inverter

If money is no object, this is one way to get lots of solar+battery energy and power into your three-phase home.


  • Fault tolerant. If one battery inverter goes down, the other two will hum along just fine until it is repaired.
  • 3 x the power of a single battery inverter


  • Expensive
  • Each battery can only backup and offset the phase it is connected to.


Configuration #11: Three batteries, three battery inverters and an inverter with a single-phase solar inverter

Three batteries, three battery inverters and a inverter with a single-phase solar inverter

Same as previous configuration, but with single-phase solar inverter – just to show it is an option for those who want more battery power than solar power.


Configuration #12: Microinverters on  a single-phase with single-phase battery inverter and one consumption CT

Microinverters on  a single-phase with single-phase solar inverter and one consumption CT

One for my fellow micro-inverter lovers. Yes, it is easy to add batteries to microinverters. But if you only have one consumption CT, you’ll only get the benefits on one phase.[1. My first battery (Sunverge) was set up like this. The installer, AGL, has decided to replace it with a PowerWall 2, with 3 consumption CTs for free. I’m not gonna stop them. ]


Configuration #13: Microinverters on  a single-phase with single-phase solar inverter and three consumption CTs.

Microinverters on  a single-phase with single-phase solar inverter and three consumption CTs.

If you want a micro inverter system with batteries, make sure you get one that can accept 3 consumption CTs like this.

This is how the Powerwall 2 battery system on my house will soon be configured.


Configuration #14: Microinverters on  all phases with single-phase battery inverter and one consumption CT.

Microinverters on  all phases with single-phase battery inverter and one consumption CT.

If you have your microinverters across multiple phases, then that is not a problem. The one disadvantage is if your battery inverter can charge from solar during a grid outage, you’ll only be able to charge from the solar panels on the battery phase. And, again make sure you have 3 consumption CTs like this…


Configuration #15: Microinverters on all phases with single-phase battery inverter and three consumption CTs.

Microinverters on all phases with single-phase battery inverter and three consumption CTs.

You get the idea.


Configuration #16: Microinverters on  all phases with three-phase solar inverter and three consumption CTs.

Microinverters on  all phases with three-phase solar inverter and three consumption CTs.

Finally – if you have microinverters on all phases and it is important to you that you can charge from all the solar panels during a grid outage, then a three-phase battery inverter with backup function will allow you to do that.


If you have a three-phase supply and want to install batteries your options are vast.

My advice If you are starting from scratch:

  • If you  want to install as much solar PV and battery power as possible, then consider configuration 1.
  • If you are starting from scratch and are happy with 5kW of solar inverter power and 5kW of battery power, then a single-phase battery inverter, AC coupled with 3 consumption CTs is a good choice.
  • If being able to charge the batteries from the solar during a grid outage is important to you, then you need a single-phase solar inverter (configuration 7). Otherwise I always recommend a three-phase solar inverter (configuration 5), as they handle voltage rise issues better.

My advice If you are retrofitting batteries to an existing system:

  • When retrofitting, your choices are constrained by what you already have installed (unless you want to throw your existing solar inverter in the bin). For most people a single-phase battery inverter with 3 consumption CTs like configuration 5, or configuration 7 is a good choice.
  • If you are retrofitting a battery and want bags of battery power available to export because you believe it is your duty to support the grid, then a three-phase battery inverter is for you (e.g. configuration 9).

Or if it all looks a bit too much, simply engage an experienced solar+battery installer, who can decide  the best design for you. Just make sure you are clear in your requirements. Tell the installer:

  1. If you want self consumption on one or all phases
  2. If you want backup on one or all phases
  3. If you want to charge your batteries from your solar panels when the grid is down
  4. How many batteries and solar panels you want now or in the future

Then your installer will know which of the 16 configurations to work with, or might invent a whole new one just for you. You can engage 3 great installers for quotes on battery systems and retrofits here.


  1. shown as black on the diagrams
  2. I haven’t even included DC coupled systems with Solar Controllers or DC Converters
About Finn Peacock

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


  1. Tony Jacques says

    Good advice. However, you need to have a good installer. The guy who put in my system claimed vast experience and insisted my 3 phase system had to be deconstructed and re-configured to single phase to handle the selected inverter and battery. Only after installation when the owners handbook became available was I able to read that both units were configured to accept single or three phase. I feel seriously ripped off, but – buyer beware I guess.

    • Justin Smith says

      You should thank him, not feel ripped off. If you can run your house on a single phase then you should. It is cheaper and more efficient.

      • Ah NO.
        This sparky wasted a heap of time reconfiguring the wiring when it didn’t need to be.
        Did he ensure the cable to the grid can handle the entire load?
        Or did he replace that to the pole/pit too?

        But generally, for any given electric motor of the same size, the 3-phase version will consume less power, start easier and be more reliable.
        Most certainly will not use less power on single phase.
        And for many installations, there is less copper required in 3 small wires versus 2 larger wires to supply the same load.

      • Lawrence Coomber says

        Justin wrong.

      • Hi we have a 10kw system with 38 panels and a 3 phase inverter on a very large house, got talked into it , has anyone come up with a battery
        system that can keep charging so
        we don’t loose power once the batteries have drained when the power goes down?
        Also would we be able to go off grid in the future thanks in advance .

        • Lawrence Coomber says

          Jo Foster:

          You certainly have options going forward to an Off Grid Solution, but of course the devil is in the detail.

          Here is a recommended sequence of step by step activities and actions that you could take that will result in your property being supplied by a fully functional, cost efficient and enduring Off Grid Solar PV + Battery Solution.

          1. Have a site survey conducted by an Off Grid Solutions professional. Above all other considerations, this is the foremost one, and its importance cannot be overstated.

          Based on the results of Step 1: a typical Off Grid Solution implementation: given your existing circumstances might then look like this: –

          2. Install another [PV-Array-B] of around 10 kW: Ground Mount / Elevated Wire [Solar PV Array]. Once again the most appropriate mounting design will be dependent on the findings from Step 1.

          3. Install a 25-40 kW [3 Ph Standalone / Off Grid PV String Inverter] – for use with the [PV-Array-B]

          4. Install a single [but modular – expandable capacity] DC Coupled Design – Li Ion Battery Storage Unit of 28-30 kWh; for use with the [PV-Array-B] and the [3 Ph Standalone / Off Grid PV Inverter].

          5. Apply to the CER for and receive a 10 kW PV System STC’s Rebate. This new 10 kW PV Array / Inverter System constitutes a fully functional Off Grid System and is eligible for STC’s Rebate accordingly.

          6. Mechanically/Electrically Isolate via [Special PV Applications Switching and Control Device] the existing 10 kW PV Array from the existing 3 Ph On Grid Inverter. Once again the most appropriate switching and control and control arrangement, will be dependent on the findings from Step 1.

          7. Electrically integrate via [Special PV Applications Switching and Control Device] both: [PV- Array-A and PV-Array-B] to functionally equal a single 20 kW PV Array.

          8. Via a [Special PV Applications Switching and Control Device] transfer the existing On-Grid 3 Phase Inverter LOADS [MSB] to the Off-Grid 3 Phase Inverter.

          Lawrence Coomber

  2. #17 – 1 battery, 3 Inverters.

    • Hi Finn and Ronald, I’ve been following this thread over many years and it’s fantastic. I currently have 4Kw of solar on Enphase inverters on a single phase and I’m looking to put another 8kw on the roof probably still using Enphase inverters. I have 3 phase power and as Citypower will only let you have 5kw on a single phase the new solar will need to go on other phases I assume? I would then like to add a battery, so would configuration 16 be best so I can still use power in a blackout as well and the solar panels still charge the battery? Does configuration 16 limit the battery options available?

      • Lawrence Coomber says

        Cam you certainly have options moving forward:

        One System Design Solution that you might not have considered up to now is to install a second discrete system of about 10 kW Solar PV using Enphase IQ8 3 Phase Micro-Inverters.

        The IQ8 Micro-Inverters have an important new intrinsic function that can be fully exploited as they are Grid-Forming Inverters in their own right, and when used in conjunction with Battery Storage and configured for 100% Backup Supply, this system can be designated as a fully functional Stand Alone Off Grid Installation, which is fully isolated from the Grid and also the existing On Grid 4 kW System.

        The Premises Load Circuits [including Battery Storage] can now be switched from the Grid to the new Off Grid Stand Alone Solution Supply whenever you choose, whilst the existing On Grid 4 kW System remains intact; unaltered; and exporting its full 4 kW potential to the Grid without servicing any load circuits.

        This Solution can be further optimised in the hands of an experienced System Integrator through well designed Switching Logic Controls that effectively manage dynamic switching between the Off Grid and the On Grid Systems and various Load Circuits based on multiple and complex boolean scenarios regarding loads; Battery SOC, and System Autonomy for example.

        Well worth discussing this subject with your Solutions Designer, and all the best with your project Cam, and timing is on your side for this project for sure.

        Lawrence Coomber

        • Thanks Lawrence for the quick reply, this solution definitely sounds interesting. Will I still be limited though by Citypower only allowing 5Kw on each phase for export or do the IQ8’s use the 3 phases so I don’t have to worry how much is on each phase. Apologies if I haven’t got it technically right. Are the IQ8’s available in Australia yet?

          • Lawrence Coomber says


            You have misinterpreted the key point of my comments [quite understandable however] because most RE System Designers unfortunately are not experienced with multiple system designs at the one premises, and even less familiar with the important details of the Renewable Energy [Electricity] Act 2000 as it relates to this subject.

            The 10 kW solution I described Cam is NOT a Grid Connected Solution; it is a Stand Alone [Off Grid] System. That means it has NO interaction or connectivity capability [ever] with the Grid and it is also isolated from and has no connectivity capability [ever] with the 4 kW On Grid System: it follows then that it has no relevance at all [ever] to City Power or the Consumer Mains Supply.

            Further, all premises [for STC’s purposes] are entitled to have any combination of up to a maximum of 100 kW of RE Power Generation Solutions installed. For example a typical Rural premises might have the following combination of installations: A. 10 kW 3Ph On Grid [general home supply]: B. 50 kW Stand Alone [machinery workshop]: C. 35 kW Stand Alone [refrigeration cool rooms]; D. 5 kW Small Scale Wind Turbine [connected to a VFD and irrigation pump system]: for a combined RE Solutions Capacity of 100 kW. This format also applies to any other premises with the important proviso that the On Grid System [only] must comply with the On Grid System Limits Rules and they vary from place to place, which in your case is 5 kW as you mentioned.

            There you go Cam – some new stuff for you to think about and discuss with your RE Solutions Design Engineer.

            Lawrence Coomber

          • Hi Lawrence,

            I have a 3-phase connected property, wired for solar, but have been dragging my feet re installing solar for a number of reasons.

            Re your earlier comments, in summary, does this mean you can have separate installs for each phase? E.g. off grid, on grid mix

            Cheers Tony

  3. Lawrence Coomber says

    Ron thanks for that, you have put a lot of effort into this very well prepared report.

    You have also brought into the frame another (unintended) consideration for some new potential solar PV customers at least; and that is going directly Off Grid at the beginning without traversing the inefficient and uneconomical route of On-Grid then to Off-Grid moving forward, which will soon become a commonplace consideration.

    I am referring to fully featured commercially focused Off Grid solutions though, for modern energy centric lifestyles, not the energy starved and problematic systems from past eras.

    Typically a modern domestic premises (starting point) Off Grid solution would be one of around 12 kW+ of Solar PV and 100 kWH+ of Battery Storage; DC Coupled to a 15 kW+ 3 Phase Standalone Inverter. A maximum efficiency well oriented design with minimal power conversions; operating at higher voltage therefore much less current, requiring much reduced lighter cabling and circuit protection. Importantly these designs are modular systems that are easily scalable up also.

    The PV component seems at first glance to be the sticking point for many domestic premises but this is not always the case. New Domestic Off Grid solutions PV mounting technologies are already available that offer alternative options to being totally beholden to inefficient oriented rooftop structures.

    Lawrence Coomber

  4. Thanks for this – how can I tell whether my home is 1, 2, or 3 phase – it it stated in the fuse box or elsewhere?

    • Finn Peacock says

      Carefully 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 you’ll have 3.

      e.g. I have 3 phase:

      • Ted Green says

        Thanks Finn, checked and I’m single phase. Similar labels to yours – “Normal supply main switch”, and there’s only one of them, and one for my PV too.

      • Dennis Mitchell says

        Can you get 3 phase 240/480v off a large solar array off grid? Just curious.
        I have an off grid situation with no chance for grid tie. I would like to have 3 phase power for motor efficiency. I know 3 phase motors have no start windings and are generally about 1/3 the physical size of the same hp single phase motors. I’m thinking 50-75 kw solar array with 200+ kwh batteries.

        • Lawrence Coomber says

          Dennis The answer is yes.

          Your Off Grid [Standalone System] design 50-75 kW with any capacity storage as required, can easily be integrated with CEC approved 3 Phase Standalone Inverters [along with single phase Off Grid inverters and Variable Frequency Drives as well]. Experienced system design will determine the optimum configuration.

          Off Grid [Standalone Systems] start with a Solar PV DC Power Source as the Common DC Supply Backbone for the power plant; which any number of Inverters, VFD’s, and other DC input PCE for specific purpose circuits; can be connected. Other ‘power conditioned’ DC supply sources [Wind – Pico Hydro – Compressed Air Storage for example] can also easily be integrated with the power plant DC Supply Backbone.

          Off Grid Standalone systems can be any size, and your spec for 50 – 75 kW is easily managed. The key metrics for Off Grid Standalone Technology/Systems are reliability and functionality.

          Some links with details about approved [Standalone and Microgrid] inverters that suit your situation:-

 Search for: SAA181890

 Search for: Manufacturer: AQUILA POWER

          Lawrence Coomber

  5. AndrewATA says

    Nice article Finn. How about a grid-connected 3-phase system using three Selectronics SP-Pro inverters, ac-coupled? Where would that fit in your list of configurations?

    • Finn Peacock says

      I’m not a SP Pro expert, but I think that would be Config #10a which I left out to see if you were paying attention 😉

      The SP Pros are the Battery Inverters.

      SP Pro and Fronius 3-Phase Integration

      • AndrewATA says

        Thanks! It’s slightly better than that though, as it doesn’t require 3 separate batteries. One battery inverter is designated as the “master”, controlling the entire battery as single unit across all phases.

        • Finn Peacock says

          So the 3xSPPros are essentially connected together and act as one 3-phase battery inverter? Effective but very expensive way to do it. Especially with 3 x Fronius single-phase solar inverters too.

          • Nicholas Parker says

            Hi Finn/Andrew,

            I want to build exactly what is shown in #10a, with the common battery across three SPPros as noted, a three phase Genset for backup, and a three phase airconditioner that requires 7kW to power it.

            The question…….The property only has 2 phase electricity. Is it possible to connect mains to the first two SPPros, and leave the third SPPro supported only by battery, solar and genset? The aircon will only be run during the heat of the day so the third phase should have ample power available when called upon by the aircon load. i am concerned the SPPro master will sense no mains on the third phase and keep starting the genset though? Can you configure this?

          • With the 3 x SP:-Pros you can use 3 phase Fronius inverters or Select Sun as well for bigger arrays.

      • Matthew Young says

        With regard to your Config #10a, I cannot see how 3 single phase battery inverters can maintain 120 degrees phase to phase. I suspect that it is not possible to do so. With that in mind, can such a configuration damage a Tesla Gen 2 wall charger, connected in a 3 phase configuration? I have been trying to find a 3 phase battery inverter, without success, to set up a battery backup configuration as per Config #16. Do you know of any 3 phase battery inverters that I can use in a backup configuration as per Config #16?

        • Anthony Bennett says

          Hi Matthew,

          Conventional hybrids aren’t capable of being coupled for phase rotation but a Selectronic SpPro system does for instance.

          Have a read here and bear in mind that things went pear shaped at Redback recently so they’re no longer an option.

          • Matthew Young says

            Can you provide me with an installer who can give me a quote for the design and installation of a Selectronic SpPro system configured for 3 phase battery backup on an existing 3 phase Enphase microinverter system. The configuration must be able to allow continued Solar panel charging of the batteries when disconnected from the grid during a grid failure.

          • Anthony Bennett says

            Hi Matthew,

            Please email [email protected] with your postcode and he can make recommendations from there.


  6. Hmm, it is interesting? You always said “don’t put batteries! Wait! They don’t pay for themselves!”
    Now you already have a battery and even trying to update it..Thanks for the advice!

    • Finn Peacock says

      I do have a battery and it does not pay for itself. I bought it to play with.

      • Dawn Browne says

        I have a question, I would like to ask you if possible.
        I am looking at changing to solar, but have a heap of questions???
        I am about put 50? solar panels on tin/colourbond roof 20 degrees from north,
        3 Phase Power connected to the 2 story 7 years old home.
        Sick husband so power bill is high approx $1,350 per quarter, usage is both day & night.
        1.Who installs Australian solar panels & approx cost?
        2. Amount of solar panels need to cover all electricity costs plus extra usage if needed with nothing going back into the grid & approx cost?
        3. How & what do I need to stop energy from the solar going into the grid & approx cost?
        4. What type of Inverter & brand will I need for 3 Phase power approx cost?
        5. What type of Tesla Battery will need & approx cost?
        6. Will that cover everything that I will need except an installer & approx cost?

  7. Hi Ron – fabulously useful post. It’s so hard to find this kind of detailed info anywhere on the web. Thanks!

    A couple of questions:

    1. “Configuration #5 & #6”: I don’t see how this provides “the benefits of battery energy self consumption across all three-phases.”. It looks to me like only one phase gets the battery’s input. Or have I misunderstood something?

    2. I am building a house with 3 phase and we hope to put in a solar system with battery (maybe a small modular one for now, and a larger one later). We will have a heat pump running on 3 phases, otherwise everything else will be on one phase (unless there is reason to spread the load?). I want to know if there is any point spending extra for a 3 phase hybrid inverter and connecting both the panels and battery to all phases, or if it is just as good to leave the heat pump running on 3 phases (we’ll never want to run that from battery) and put everything else on a singe phase? I don’t know the cost difference between a genuine 3 phase set up and a single phase one (do you?) but I imagine it is quite a bit extra for little gain. Thoughts?

    BTW, I have read about the IMEON 3-phase hybrid inverter: (add this to your other two available in Aus!). It sounds smart, but no idea what the cost is compared with their 2-phase inverter. No idea of their reliability, etc. either.

    Keep up the great posts!


    • Finn Peacock says

      Bloody Ronald – always wallowing in my glory!


      1. It is explained in Configuration #3:

      “They can then export enough on the connected phase to offset grid imports across all three-phases. When this battery power gets to the 3-phase meter, the meter subtracts the power being exported on the battery phase from the power being imported on the other 2 phases to give you zero net imports as far as your billing is concerned.”

      2. I’d go for a single phase battery system with 3x consumption CTs, unless you have an enormous heat pump and want to run it off battery power.

      • Ronald Brakels says

        Heh heh heh… The glory is mine now!

      • Philip Roach says

        On April 26, 2018 Jon wrote about wanting to instal 3 phase in a new build on Sapphire Coast NSW. I am wanting to do the same so I can run Stiebel Eltron hot water heaters in bathrooms and kitchen. Instant hot water, no wasted water waiting for hot to arrive. Any advice regarding solar set up and battery? Love your work, Finn.

        • Ronald Brakels says

          Hi Philip, Ronald here.

          Looking up the Stiebel Eltron hot water heaters I see one model can draw up to 19.4 kilowatts while another can draw up to 28 kilowatts. With a normal hot water system it is possible to heat the water using solar power during the day, but with these most of the power will come from the grid. A way around this would be to have the water to the Stiebel Eltron units come from a conventional hot water system that uses solar power during the day, but you would probably be better off using the money to install a larger solar system than you would otherwise.

          With three phase power you can install as large a solar system as will fit on your roof. I recommend putting as much solar as you reasonably can. The return is good even if you only use a small portion of the solar electricity yourself. Just make sure you get a decent feed-in tariff on your electricity retail plan.

          At the moment batteries won’t pay for themselves but you can add a system once they are cost effective. If you are concerned about blackouts, unless they are a very common occurrence, a small generator should be enough to get you by.

      • A Hypothetical “laboratory” operates at night and draws 3kW from a 3 Phase system set up as per Configuration #5.
        At night, the battery supplies 1 kW to the Lab and and 2kW to the grid.
        The lab draws 2 kW from the other 2 Phases connected to the grid.
        How would this be charged? How about in Perth WA?
        1. “Net metering” – no charge.
        2. Import/Export metering – 3c/kWh out, 28c/kWh in, Net 25c/kWh
        3. Something else. I tried to calculate the power factor for this system and my head started to hurt due to the negative Phasor. Will the meter have a similar migraine and still charge for usage?

        I found a 2015 article written by Finn hinting that there may be some shenanigans in how power utilities do this. Has this been resolved?

      • Thanks Finn,

        I purchased a house with solar set up that i believe is config 5. I need to replace my air conditioner and I was weighing up the benefits of a 3 phase or single phase air con with a view to using my batteries to supply some of the power required at night. My understanding is that the larger (over 15kw) aircon units are more reliable and quieter as 3 phase rather than single and therefore this would be my preference.

        Is the role of the CT’s to monitor the imported power across all 3 phases so that the batteries can then release power to balance the amount being imported?

  8. Ian l Gittus says

    Sonnen and Imeon are other options.

  9. Dave Ritson says

    OK, so what 3-phase battery inverter options are there available? (Or 3-phase hybrid all-in-one)

  10. Hi Finn,
    Is that red sign correct. Do you have only 1 solar panel connected?


    • Finn Peacock says

      I have 24 x 250W panels connected. I don’t know about you but my screen is not wide enough to put them all on the diagram!

  11. Scotty’s question related to the first picture you put up which shows the “Warning dual supply” label and Voc is shown as 37.4V which surely can’t be more than one panel.

  12. Maria Gardiner says

    Hi Finn

    Thanks for this. It is much appreciated. I am about the get a Tesla powerwall 2 installed on the AGL VPP (replacing the sunverge) and am on 3 phase. I don’t have much that runs on the 3rd phase – my aircon (which sucks the power like crazy so rarely use it at night – just run it during the day), the stove and a couple of outside powerpoints.

    I have found that i probably use around 50-70% of the battery just with usual overnight consumption. I wonder if it is worth it to have the third phase on the battery as well so that stove can draw from the battery? I guess it depends on how much they slug me to do this. Also in terms of having the 3rd phase on the backup, i only have a small bit of the 1st phase on the backup (just the fridge, the lights and a couple of powerpoints). Would there be any need to have the 3rd phase on the backup?

    Am i understanding this all correctly? Which option do you think i should push for when they install the powerwall? Assuming they will let me have any options at all!


    • Finn Peacock says

      The Tesla Powerwall 2 is a single phase battery system that can be used with 3 consumption CTs. That means it can be configured to give you the benefits of battery self-consumption across all 3 phases despite only being physically connected to one phase.

      Next time you talk to AGL, just say this:

      “Please can you confirm that I’ll get rewarded for self consumption across all 3 phases?”.

      • Maria Gardiner says

        Thanks so much Finn. I just rang and asked and they confirmed yes! But I will be hovering when they do the changeover to make sure.

        I have another question that is not a three-phase question so not sure if it is okay to ask here. And if you have addressed it elsewhere I’m very happy to look there if you point me in the right direction. But have you discussed or thought about or calculated the optimal amount of power to leave in the battery to use for backup? It seems if you leave a higher percentage (20%?) then there’s all that wasted power just in case there is a blackout. But if you run the battery down to its permitted lowest point and there is a blackout you will be kicking yourself because the one time you needed this bleeping backup (that you paid $900 for!) it is not available.

        • Finn Peacock says

          Excellent question – and it is totally up to you. I just leave mine on the default setting and hope that any blackouts are not in the morning before 11am! But if your PW2 is set up to work with your panels when disconnected from the grid, then even if you are blacked out from sunrise, the solar will recharge the batteries as the sun rises.

        • Hello, thanks so much for the really detailed article.

          I currently have a single phase system with Tesla Powerwall 2 and 7kW of panels with Enphase micro inverters. I’m just about to upgrade to 3 phase as current set up can’t handle power requirements of oven, water heat pump, AC, etc and install of new electric induction cooktop is going to take us over the limits of 1 phase. From what I have read here, what I need to do is ensure that the Powerwall gateway “connects” to the two new phases with consumption monitor so that when using power from one of the new phases, the Powerwall gateway will push power back into grid to balance.

          Do I need to get a specialist in to reconfigure my Tesla gateway?

          If I were to add more solar, would you have any recommendations on how to do this post install of the three phase? I believe that upgrading to 3 phase means I can generally get approval for a higher kW grid connected solar install. I’d like to install it all onto same phase as my battery, but not sure that is allowed given the Powercor/Citypower limitations. Do you have any advice here?
          Thanks in advance! Chris

          • You will hopefully have an easier/cheaper course than me, as you chose microinverters over the optimisers and inverter setup.
            There are other considerations apart from the DNSP requirements.

            I have recently upgraded to a 3-phase supply, around a 5 year old 6.27 kW SolarEdge system installed on a single phase with panel level monitoring and full consumption monitoring.
            I now wish to upgrade my solar to cover the 3-phases to get some export balancing across phases and perhaps, add a battery at a later stage.
            But the main problem encountered is the age of my system. As I understand, any upgrade or alteration (not repair) that involves my single phase system, requires that it be recertified to current AS/NZS Standards and CEC Approvals – effectively meaning it is easier to junk it and install a completely new 3-phase system. STCs are another consideration – it would be easier if I didn’t need to claim them. Older panels and inverters drop off the CEC Approved list and no installer is interested in going through the process of certifying another installer’s work and taking on the risk of liability for warranty or catastrophic failure.
            Apparently the best that installers can do for me is to add another single-phase 5kW SolarEdge system and retain the old 6.27kW system untouched.

  13. I realize you were no doubt trying to keep the schematics simple, but if we are talking about backup, don’t we need to also include some auto transfer/isolating switch/contactor arrangement. Please discuss.

    • Finn Peacock says

      Yes – you absolutely need a switch if backup is required and to also think about:

      Which circuits are backed up
      Backup circuits sub-board
      Battery bypass switch in case of battery fault
      If system can charge from panels during outage – and how? Comms or Frequency shifting
      Solar array size relative to battery inverter power for charging

      I think that is a whole other blog post!

  14. Thanks – I look forward to it 😉

  15. Jim Raleigh says

    A very useful article but does not actually cover my specific (admittedly unusual) situation.
    I have a 28 panels (8.96kWp) connected in 2 strings (16 &12 facing in 2 directions) to 2 single phase (Solar Edge 6500) inverters each of which has one of the larger (RESU 10H) LG batteries attached and are connected to 2 separate phases of the 3 phase supply. Both inverters are configured to give me backup power on the relevant 2 phases.
    I am told that if one battery is charged and the other is not, it has been configured so that the second battery will be charged from the first string by feeding through the smart meter, and that consumption on the third (no solar) phase is taken care of by the smart meter using output from the solar connected phases.
    I have certainly seen a dramatic drop in my imported power and am exporting quite a lot, enough production to run my air conditioner through the recent summer and still get a negative bill.
    I do expect that it will not be so good in the winter as I have a large house and heating (in Canberra) can be a significant cost, but am waiting to see.
    Is my configuration as optimum as it could be or would I be better with changes.?
    PS: A side impact of my configuration that may interest you is that although I have a Reposit box installed, it is no longer connected. The reason is that to handle my situation I am told (by Reposit) that I would need to have it changed to a Reposit Infinite, but that if I did so, I would have to separate the two phases into 2 totally independent Solar systems rather than run the Inverters in a Master/Slave configuration as at present. This would prevent me monitoring the entire house as a single entity which I see as important.
    Secondly although it was originally connected, we discovered quite by accident that it was interfering with the Solar Edge monitoring, such that I had no visibility of consumption data, a fairly fundamental requirement. Once it was disconnected the Solar Edge monitoring worked just fine.

  16. mark wilson says

    awesome article and great discussion too, thanks guys

  17. Thanks for the helpful article.

    I am in the process of building a 3-phase house including an off-grid Solar system. Solar panel capacity 12.2kW in two strings and planning 2 LG Chem Resu 9.8kWh batteries. Originally Fronius Symo 10kW inverter proposed, then 3 Fronius Primo 4kW; both with 3 Selectronic Battery Inverters 5kW 48V. Questions are now (suddenly, after almost 8 months) around the suitability of both the batteries and the inverters. I am now starting to query the advice I have been given.
    Has anyone got helpful ideas or experience with this type of system that I can use to assess the info I have?

    • Lawrence Coomber says

      Hi Joan.
      If you are considering a 100% Stand Alone Solution Joan (not a hybrid solution) then the most cost efficient, reliable and enduring option for you to consider might be a DC coupled single 3 Ph inverter system.

      2 x LG Chem’s; 3 x Froniuos Primo’s and 3 x Selectronic Battery Inverters sounds about the opposite of simplicity; functionality and endurability. Can I ask Joan what has prompted you to now start to query the advice you have been given?

      Lawrence Coomber

  18. A helpful article. I have a question or two. I’m considering battery storage. My system was installed in Dec 2017. It’s a 3 phase Fronius inverter (not hybrid) was advised at the time not to spend extra money on this type of inverter as not needed for adding battery storage later. So what are my battery storage options I assume I have more than one.

    • Ronald Brakels says

      Hi Pas, Ronald here.

      The easiest way to add battery storage to a home with an existing solar system is to AC couple it. This involves installing batteries with a battery inverter that provides DC power to charge them and changes DC power from the batteries into the AC power homes use. The most well known AC coupled system is the Tesla Powerwall 2. It has a built in battery inverter. But other batteries such as the LG Chem Resu can be AC coupled with a separate battery inverter. If you check out our battery comparison table:

      You will see there is a row which says “ÄC or DC Coupled?”. You can use this to see which are specifically made to be AC coupled. Where it says “N/A” it generally means it can be AC coupled using a separate battery inverter.

      As you have 3 phase power you are unlikely to have problems with inverter limits when you install an AC coupled battery system. (Unless your solar system is very large.)

      At the moment batteries won’t save you money, but so long as you are fine with that, good luck getting a battery system.

  19. Hi Finn,
    Reading Jim Raleigh’s post above interested me (no one has replied to him yet!). He is wrestling with large systems on a 3-phase supply – as I plan to too. My question relates to choosing between 3-phase and 1-phase inverters. I don’t know the relative costs of these inverters, but is there a “sweet spot” in terms of PV size and how to manage 3-phase or 1-phase inverters? E.g one could presumably install 2 small 1-phase inverters, or one larger (more expensive?) 3-phase inverter. I am contemplating 20 kW, so should I just be doubling up and using a separate inverter for each phase, or looking for a large 3-phase inverter? And presumably there is an optimum PV size that gives you most bang for the buck as far as available inverter sizes go.

    BTW, I will have most usage on only one phase, the 3 phases only being used for heating which I don’t expect to be able to manage from the solar anyway, even with 20 kW of PV!

    • Finn Peacock says

      In terms of solar inverter cost you’ll save about $1000 total with a good 15kW 3 phase inverter compared to 3 x 5kW single phase inverters (perfect for 20kW of panels).

      A great solution for big 3 phase solar and battery systems is the SP-Pro + Fronius (AKA Spronius).

      There are lots of factors to consider with 3 phase and batteries, as you can see, such as how you want your backup and self consumption to work, the resistance of your grid connection etc. So you really need a clued up installer with lots of battery experience to have a good look.

      • Thanks Finn. But I am confused by Spronius! Why do I need SP-Pro as well as Fronius. Aren’t they both inverters? I only plan to back up one phase, but want the solar to feed in on two phases. Does this make a difference?

        • Finn Peacock says

          The SP Pro is an AC coupled battery inverter. The Fronius is a solar inverter. The SP Pro talks to the Fronius inverter so the solar panels can be throttled when there is not grid available. This allows the solar to charge the panels without a grid.

          If you don’t have that comms link – the system will work fine, but if the grid is disconnected, once the batteries are flat they will not be able to recharge until the grid is reconnected.

          If you only want backup on 1 phase then…

          Advantages of 3 phase solar inverter:

          Cheaper hardware (about $1000)
          Cheaper installation
          Lower voltage rise to the grid (may or may not be an issue – depends on your local grid and how thick your grid connection wires are – you need a good installer to advise)

          Disdvantages of 3 phase solar inverter.

          Can’t use solar panels when grid goes down, because inverter needs to see the grid on all 3 phases to fire up.

          Advantages of 3 x single phase inverters

          Redundancy – if one fails you still have 2 phases
          You can run the solar panels on the backup phase without the grid.

          If ‘apocalypse proof’ backup is not an issue then I’d personally go for a 3 phase solar inverter and a single phase battery.

          • Hey Finn.

            Redundancy depends I guess on where you are. Energex requires single phase inverters on multiple phases be interlinked so if one goes down they all do.
            At the time of writing I think Fronius Primo with additional software from Fronius can do it, but everything else needs a combiner box.


  20. Thanks Finn, very clear! So presumably a 3 phase *hybrid* inverter (e.g. Imeon, Solax) will do everything, including powering and charging from solar when grid is down? But it seems they don’t come with higher power levels.

  21. Hi Finn, thanks for the good article and advice! I have answered most of my questions by reading the article and previous questions and answers, but I would like to double check this last question.
    Our new system will be a 13Kw solar + PW2 on 3 phase power. I believe the inverter quoted is the Solaredge SE10K 3 phase inverter. CTs to each phase. Configuration #5 or #7 (but with a 3 phase inverter).

    From the 3 phases, I think we will request to use just 2 – one for the running everything in the house (with different circuits – PW2 connected to this phase) and the other phase dedicated to the Sanden HWS (with a timer to operate from about 11am to 3pm from the solar system). – The extra phase will have a CT installed just in case we need to use it in the future.

    In case of a blackout, the PW2 will be set to power a couple of circuits from the battery phase such as lights and dc ceiling fans and maybe one area of powerpoints.

    Is there any way that we can configure this system in a way that if we do have a blackout during daylight hours the system will be able to:

    Solar panels to continue charging the PW2?
    Solar panels to power the house if the PW2 is full or if the second phase requires power (HWS startup times)?

    Thanks for your help and great advice!

    • Ronald Brakels says

      Hello Nico, Ronald here.

      The Powerwall 2 has full backup capability and, according to Tesla, during a blackout it can be charged by your solar panels. During the daytime during a blackout power produced by your solar panels will first go towards meeting household electricity consumption with any shortfall being make up by the Powerwall 2 storage and any surplus will be used to charge the Powerwall 2.

      Unfortunately, unless you have a Powerwall 2 lined up, it may be hard to get your hands on one. Tesla says they won’t be available until early 2019.

  22. Mhanks Finn

    That is a great help as I can now show my installer what I need. Little understanding of three phase by most of them! For Config 7 are there other battery inverters that are available apart from Tesla?


  23. Not sure if you are still reading these posts, Finn, but here goes just in case…

    I plan to have 3 phase power, with a 3 phase 16 kW hydronic heat pump plus the rest of the house on either just one or all 3 phases. We’ll have a battery set up to run as backup for grid outages (need to pump water, sewerage, etc.). But, if the power goes out, I don’t want the battery to power the heat pump as that will flatten the battery in about half an hour! Is there any way to prevent the heat pump from being powered by the battery?

    • Ronald Brakels says

      Hi Jon, Ronald here.

      First off, I’ll mention that it can be much cheaper to use a generator to get through blackouts than batteries. So if cost is a consideration you may want to hold off for a while and see how much they fall in price.

      A 16 kilowatt heat pump is enormous and so I am thinking that might be its heat output and its electrical power draw would be 4 kilowatts or less. But that’s still enough to grain a battery.

      When you get your battery installed you can just have all your vital loads on one phase which your battery is connected to. Your 3 phase heat pump wouldn’t be able to run off that. But your installer might have a more elegant solution for you which will depend on what hardware you are getting.

  24. Andrew Hunt says

    Is it possible / practical to have the current SolarEdge 3 Phase 5KW inverter easily connected to a battery. Asking for future proofing of a quoted system. I have heard mixed reports. Some saying it is easy. Others saying it is not feasible.

    Thanks in advance

  25. One other possible configuration I am planning to implement is as follows:

    My house has 3 ph and I’m on a high FiT and limited to my initial/legacy install inverter sizing, in my case 3Kw. I have 22 panels in 2 different orientations NE and NW on a dual MPPT inverter To maximise export and FiT revenue, I have removed all internal house loads off the solar phase L1 (my inverter is single phase). and put those load on the remaining two phases.

    I have a further 45 panels ready to connect up mounted on a rear shed. These will feed through a single phase 10kVA off-grid inverter and charge my EV which will also be a storage source for my house supply. The two phases servicing the house are disconnected from the grid and become common (joined) serviced by the single phase inverter which at 10kW has adequate short time overload capacity for all internal house loads. Fall back to the grid is automatic by a transfer switch. I plan to wire the panels in a 5x per string format which means the EV battery can also be charged directly from the panels in an emergency (ie if the inverter ever failed.

    • Lawrence Coomber says

      Ian you have strong options from what you have on hand.

      A simple generation solution to consider – why not use your 45 panels to their full advantage and connect them to a 20 kW 3 Phase Stand Alone Inverter and “dedicated selected premises load circuits” to this Off Grid Strategy which is totally isolated from your existing On Grid System that is on a high FIT.

      This is a common strategy particularly for rural premises where pumping and irrigation circuits (or high current low duty cycle machinery) for example, are independently serviced by a second (and isolated) Stand Alone PV system.

      The extra bonus with this strategy is that you can easily connect a very efficient DC coupled battery stack to the Solar PV DC Bus and through “dynamic smart controls” exploit the battery stack to full advantage for the entire premises night time loads.

      Something worth discussing with your energy systems design engineer for sure.

      Lawrence Coomber

  26. Jason Dickinson says

    I have installed a few AC retrofit inverters with battery storage on single phase houses with no issues.

    Now I have 3 phase costumers with existing PV systems (dc and enphase) that want batteries.

    Is the financial benefit that same if…..

    I use a single phase retrofit inverter and install 3 CTs, this will discharge into the connected phase and then subtract the excess into the other 2 phases.


    Do I wait for a 3 phase retrofit inverter to be released therefore discharging to each of the 3 phases evenly as required by the loads.

    Finn, be good to hear your point.

    I know goodwe are releasing a 3 phase retrofit this year.

  27. Finn,

    Hoping you are still replying on this topic.
    I am going through the quotes process and two installers propose Fronius 8.2 based system. We have 3 phase and want all 3 phases connected. That would mean Fronius Symo. Plus consumption metering. Considering just under 11kw system.

    Although we dont want the battery now I’d like to make the system is designed with it in mind and with ability to charge battery as well as power all phases, not only emergency circuit when grid is down. We are not heavy users of electricity at around 10kw per day so we might get away with this.

    My question is, which configuration would you recommend for this? The suggestion in your main post above is Configuration 5 but, as this does not refer to gear that disconnects the solar system, it does not compute for me with the advice you provided in the blog here:

    I guess, all I need at my stage to determine if Fronius Symo 8.2 is good (go with something like PowerWall 2 in the future via AC coupling at switchboard) or is a hybrid version of an inverter (DC coupled) a better choice in my case. Don’t even know if there is a Symo hybrid version.

    Would appreciate a POV on this.

    • Finn Peacock says

      If you want an AC coupled battery (like the Powerwall 2) that can provide backup AND charge the battery from the solar panels during a grid outage then do not buy a 3 phase solar inverter:

      (I’ve updated the support post to point this out!)

      If you want to power all 3 phases of the house with your battery during an outage then I would look at a 3-phase Fronius Symo Hybrid inverter. They are now compatible with BYD B-Box batteries, and together would be a good system.

      • ‘”an AC coupled battery (like the Powerwall 2) that can provide backup AND charge the battery from the solar panels during a grid outage then do not buy a 3 phase solar inverter” – I think I need to buy a 3 phase inverter as battery is a future option only and we would like the PV connected to all phases. May never buy a battery, who knows.

    • Ronald Brakels says

      Hi Tony, Ronald here.

      If you are not planning to install batteries for a few years there may be no point in doing anything to prepare your home for them. There are likely to be major changes in the home battery market in that time. But no matter what you should still be able to AC couple a battery to your home. (With 3 phase power you should have no problems with inverter limits.) I expect there will be more 3 phase battery options available in the future.

      If you want your solar system to immediately be ready for batteries you could install a Fronius Symo Hybrid but this only goes up to 5 kilowatts and at the moment, as far as I am aware, is only compatible with the expensive Fronius battery or LG Chem RESUs. It also only has 1 MPPT which means all solar panels will need to face the same direction and have the same orientation.

      If you keep your current plan of installing an 8.2 Symo then in the future you could get a battery using configuration 5, 6, or 9.

      If you instead decide to install a hybrid inverter now then you will be limited to getting a battery which is compatible with that inverter in the future. And that may not be the best battery available then.

      • Finn Peacock says

        Good point – I forgot the biggest Symo Hybrid is a wimpy 5kW.

      • “Fronius it Symo Hybrid but this only goes up to 5 kilowatts and … also only has 1 MPPT” – both constraints would not work for us. Especially 1 MPPT as we are installing on panels on 2 degree roof sides towards east and west.

        OK, it means the hybrid Fronius is out.

        It would otherwise be a great option, as in my opinion, you could still AC couple any AC battery (its an inverter anyway) and still have another option for inverter compatible batteries. Win win… but not with these constraints.

        So my only option are only to install Fronius Symo 8.2 and in the future look for a decent 3 phase battery setup.

        Am I missing anything?

        • Ronald Brakels says

          There is the option of installing a three phase hybrid inverter from a different manufacturer that’s of suitable size, but it may not be as reliable as a Fronius. If you’d prefer not to do that then you can wait and see what 3 phase battery options are available in the future or settle for a single phase battery system.

    • Jason Dickinson says

      Hi tony
      I have just completed an installation using a solax x3 for a three phase house. Complete with batteries and EPS. This and the Fronius were the only 2 options I could find on the market for 3 phase hybrids.

      I have pics on my FB page of the install.

  28. Hi Tony,
    For what it’s worth, I have similar needs to you (3 phase, want PV on all phases for voltage balance reasons, want battery in near future, but not yet, etc). I have decided to add 15 kW of PV (mad not to max out roof space, esp. since government gives STCs, which will be worth less if we decided to add more PV later instead) and am planning to install a SolarEdge 8 kW 3 phase inverter on 10 kW of PV, and a 5 kW SolarEdge hybrid inverter for the remaining 5 kW. Will attach a battery later to the hybrid. I figure 5 kW should be sufficient to charge a future battery (probably a 10 kWh LGchem).

    Is that mad I wonder? Comments welcome!

  29. Lawrence Coomber says


    If you are seriously contemplating moving forward with a ~15 kW Solar PV Power Plant, and you are in a domestic circumstance (rather than an industrial or commercial one with heavy duty cycle power consumption circuits and equipment) then you have sufficient Solar PV available to consider installing a fully functional Standalone Off Grid 3 Phase Solution at the outset, and abandon the grid service connection entirely. You will receive all of the same Government benefits on offer; STC’s etc for Standalone Installations as On Grid Installations.

    15 kW of PV as a primary power resource is about the right value for a substantial (domestic) DC bus system when coupled to a ~10,000 AHr battery (480 V nominal) and a 3 Phase Standalone Off Grid Inverter (25+ kW), and this would prove to be a very efficient, reliable and endurable ‘smart’ power plant with 24/7 x 365 autonomy.

    Open ended Solar PV DC Bus systems importantly allow for simple system upgrading by adding more Solar PV at any time in the future as changing load circumstances might require, including connecting efficient and cost effective Variable Speed Drives (VFD) for specific motor driven equipment circuits such as pool pumps, irrigation pumps, watering system pumps, and surplus power water heating automation for example.

    Something certainly worth discussing in more detail with your local RE systems design engineer Tony I would suggest.

    Lawrence Coomber

    • Ronald Brakels says

      While many people like the idea of going off-grid, economically Tony will be far better off staying on the grid and receiving a feed-in tariff for exported solar electricity. If desired a generator can provide backup during a blackouts at much lower cost if required. It’s also far better for health and the environment. Staying on-grid could easily lower CO2 emission from electricity generation by over 16 tonnes a year.

    • “15 kW of PV as a primary power resource is about the right value”

      Lawrence, when we started thinking about PV years ago that’s exactly what the initial idea was… be self sufficient and do the right thing. Move fast forward to today. We have a new house now with decent amount of roof space. We are in United Energy, Melbourne area so feed limits are not crippling. I am also more aware of what’s the solar ideas practicality perspectives are. Putting money forward is not an issue but eventually that needs to stand an economic sense; e.g. we could buy a PV plus batteries today but, that batteries bit, is that makes no sense to me in a domestic situation (today).

      Maybe in a micro-grid situation it would be a super fantastic idea. Why wouldn’t the energy industry, for example, connect say a 1mwh battery to substations? There are typically biggish buildings with empty space around them… a bit of wasteland… opportunity for lots of storage for everyone to benefit (not just people with money for PVs). My (and others) PVs could help charge this storage during the day to be ready to shift or eliminate the peak at least partially. And to help us accommodate the EVs, when we all can afford them as commodity (you would have no chance to charge an EV from your domestic battery overnight)

      If one had a chance to attend the Australian Utility Week yesterday, you would have heard a CIO from a distributor saying they wanted to do something like this already (Transgrid in Sydney) but the regulation prohibits them from connecting such facility (they built it)…. because they only have a license for distribution… and connecting storage would require them to be … a generator. Call it whatever you want but it just shows how lagging is energy regulation in this country. Not going to happen in Victoria too as the regulation in our “deregulated” market also prohibits distributors to have “generation” abilities. Retailers can.. so they can self justify energy prices increase… but Finn has discussed that elsewhere already.

      Anyway, to cut the story short. Our electricity monthly bill is $90 as we have a number of energy saving things in place like builtin split system aircons instead of one monster duct-ed system and poorly insulated buildings the builder are pushing and producing.

      To Ronald’s point, I can see a return on my money in maybe 7 years with current FIT and my considered 11kw system. Maybe in 5 or sooner if electricity keeps going up. What would be economics of the off-grid?

      Not to mention that all these batteries will die (even with so much Tesla marketing spin and super sleek, but heavily obfuscating, software in them) and you will face a piece of junk you have to get rid of and replace. Will there be a system here to recycle these batteries or will we be still shipping our recycling to China to bury them at our expense?

      So, in my simple mind, a grid connected PV without battery is both the most economical and environmentally friendly option in a suburb.

  30. Lawrence Coomber says

    How you have managed your energy plant project so far is a good example to others. You have done your research, asked meaningful questions of others involved in the sector in a variety of ways, evaluated all the feedback and drawn the best conclusions that suit your vision going forward.
    Well done and all the best with your future installation.

    Lawrence Coomber

  31. Hi Finn,
    I have an Enphase solar system connected to a single phase of 3 phase power. So at the moment if the appliance I’m using isn’t connected to that phase I can’t self consume during the day. I want to be able to use as much power as possible and export little. Also I would like it to backup and the solar panels still work in a grid outage. What’s the best solution?

    • Ronald Brakels says

      Hi Cam, Ronald here.

      Your electricity meter takes the total of the power being exported from your home and subtracts that from the power from the grid being drawn by your home to determine how much power is being consumed or exported. This means, as far as your meter is concerned, you can self consume if you use power from a phase your solar system isn’t on. For example, if the phase your solar system is on is exporting 4 kilowatts while appliances are drawing 2 kilowatts on both of the other two phases, as far as your electricity meter is concerned your aren’t using any grid power at that time.

      If you are looking for back up power the most cost effective option is to get a generator. This is because at the moment battery systems can’t pay for themselves without a subsidy. If you do want a battery system you may want to wait a year because, depending on who wins the federal election, a $2,000 subsidy may be available.

      If you do want a battery now you can see if there is something that suits your needs on our battery comparison table that has off-grid capability:

      • Hi Ronald,
        Thanks for the quick reply. Thanks for clearing up the consumption and export on 3 phase. Understand your thoughts on waiting. If I did want a battery would configuration 13 be best so as you could use the battery power on all 3 phases and still have solar operating in an outage?

        • Ronald Brakels says

          #13 would be good. You will want all your essential loads on the phase with the battery as anything on the other phases won’t be able to make use of battery power during a blackout. At minimum that would be refrigeration, lights, and at least one power point.

          • Ronald is there a battery that can be on all 3 phases, to have whole of house backup or do you then loose the ability to have solar generating when the grid is down? I also noticed this article

            talking about Tesla releasing a battery for 3-phase households.
            Thanks again for your insights,

          • Ronald Brakels says

            Here’s an article I wrote on the current Australian price of the Powerwall 2:


            You are looking at about $15,275 by Tesla’s figures. I don’t know if a three phase solution for the Powerwall 2 is available at the moment.

            As odd as it may sound, you could install a hybrid 3 phase inverter with additional solar panels and connect a battery to that. Because of the way the STCs that reduce the cost of solar work, the additional solar panels will cost you very little while the hybrid inverter will be able to provide power from a battery to all phases during a blackout — although the total amount of power will still be limited. The batteries will be able to charge off the additional solar panels during a blackout and if you also connect a small generator to the hybrid inverter you will be pretty blackout proof.

          • Finn Admin says

            I believe the new Gateway for the Tesla Powerwall 2 improves the way it handles 3 phase. I’ve been told it spreads the battery power across all three phases in normal (grid connected) operation, but can still only power 1 phase in backup (no grid) mode.

          • Ronald Brakels says

            I just spoke to a Tesla rep who confirmed that. He said there is currently a 12 week wait for the Powerwall 2 and was unable to confirm if the wait period would be the same for the 3 phase version.

      • John Peterson says

        Hi Ronald
        Does that extend to solar on two phases only of a three phase system? In other words if two single inverters are feeding two individual phases does a 3p smart meter do a similar calculation for instantaneous consumption? IE if the only phase without solar has the 2 kw load and each solar phase is producing 1 kw load is that a zero net consumption?

    • Finn Admin says
  32. Hi Finn,
    This is a great article, well done.
    Just a quick question.
    In our case, Configuration 5 would be appropriate as we have a 3 phase solar inverter working well.
    It might be me, but I’ve had difficulty locating an AC coupled battery inverter/charger that has 3 CT inputs.
    Can you please advise what options are available?
    Many thanks.

  33. Hi I have a system that consists of 2 x fronius symo inverters 1 x symo 15 with 13300 kw of panels and 1 x symo 6 with 5890 worth of panels im looking towards battery power and configuration 8 is what im after

    However i cannot find a manufacturer that make a true 3 phase battery inverter to suit my system i would like to run 2 x resu10 batteries as these are starting to become cost competitive can you recommend an inverter that would be able to keep up and suit my system ?

    • Ronald Brakels says

      A Selectronic 3 phase multi mode-inverter should work well. While Selectronics products are considered high quality I’ll let you know they’re not cheap.

      • just looked at their pricing def not an option @ 45,000 for a 3 phase inveter to suit was ideally looking around the 4-5k mark techs just not here yet and cost affordable

        • Ronald Brakels says

          They’d be a lot less than that but probably still a good way above your 4-5k budget. Contacting Selectronics would probably be the best way to get a solid figure.

  34. Lawrence Coomber says

    Jason at those PV values, you may have generation plant options you haven’t yet considered.

    It all depends on your premises circumstances of course, which you haven’t described but nevertheless 19 kW of PV is a sweet spot with some extensibility for a 30 kW Standalone (SPS) 3 Phase String Inverter suitable for any combination of DC Inputs (typically Solar PV; Battery and or Capacitor Storage System) but other DC input sources are also suitable.

    Understanding how to design for the best use of a robust and enduring multi input source DC Bus backbone for renewable systems is well worth learning about.

    Three phase supply is of course necessary for three phase motors which may include irrigation (surface or bore pumps), welders, ovens, and a host of other multi phase equipment.

    Single phase services are important also and most people get lost on this subject because from an efficiency and cost effectiveness standpoint, any PV System can be designed as a common DC Input source to both 1 and 3 Phase conversion equipment to power dedicated 1 and 3 phase circuits. This also opens up the question on using VFD’s for rotating machinery applications where appropriate (most applications can benefit from VFD use).

    I would be interested to know a bit more about your situation Jason and maybe have some more tailored advice for you to discuss with your energy engineer.

    Lawrence Coomber

    • 16mm2 incoming consumer mains x 3 underground SDI’s approx. 20m run
      We have the ability to go to around 26150 of PV panels once our rear house extension is complete and we gain some extra roof space all north facing.
      Have also tossed around the addition of wind generation as we are in a gully and get quite consistent and strong winds this would be added to the symo 6 as it is at capacity for roof spacing and panels where it is right now.

      Current best production to date has been 110kwhrs in 1 full sun day in saying that we are having issue with incoming line voltage tripping the inverters SAPN are replacing the transformer in April to mitigate this a tap the new one down on blue phase

      House is well balanced load wise and somewhat equal have 3 x split system AC and 1 x reverse cycle ducted all single phase

      Only 3 phase equipment is in my workshop have a compressor and hoist on 3 phase so not overly large drawing equipment hoist is used infrequently along with compressor.

      Monitoring my smart meter we use approx. 7kw overnight taking into account a 12hr period of no usable sun or 9.6kw if we run our bedroom split system during summer so would like to mitigate this usage overnight and also feedback into the grid to profit even more from our excess generation.

      Very interested to discuss options on how to maximize as i feel it is really going to waste at 10c feed tariff although it produces excellently (when its on Thanks SAPN)

      Jason Bretones

  35. I am absolutely delighted to have found this discussion.

    I have asked a lot of people the same question, and I continue to get different opinions, and this site makes it clear why this is the case with so many possible installation options.

    I have a 3-phase home using a 3-phase FIT tied SolarEdge inverter with optimizers due to siting and shading issues, and after several years I would like to explore the possibility of adding a NiFe (Nickel-Iron) battery bank.

    My installer tells me that this inverter will only accept a Lithium chemistry using the StorEdge box.

    Other installers tell me that I will require an AC coupled installation using three inverters with a battery bank tied to each inverter allowing me to leave my current installation alone.

    Neither of these ideas suits me. The first one uses the wrong battery chemistry for me, and the second is too expensive.

    I am hopeful that perhaps someone here can share an alternative idea.



    • Ronald Brakels says

      A Victron Multiplus inverter/charger can apparently handle nickel iron batteries. I presume it would be connected to one phase and you would need to put all the loads you wish to be battery powered on that phase.

      If nickel iron batteries are what you want, that’s fine. But if the economics of the battery system are important that’s fine you should be able to find a more cost effective battery option. (I generally recommend waiting as battery systems should continue to fall in price and more information will become available about which are reliable. There also may be a federal subsidy of up to $2,000 starting in 2020.)

  36. Ronald,

    Thank you. This sounds like a promising idea. I am assuming that this would be AC coupled with my existing SolarEdge inverter.

    Would this correspond to one of the above configurations previously described?

    I chose the NiFe chemistry based on some of the properties it offers:

    1- More lifetime cycles than lithium or lead batteries
    2- Sturdy performance through a larger range of temperature swings
    3- More tolerant to over charging
    4- More tolerant of deep energy discharges
    5- No acids or corrosive liquids
    6- Easy maintenance by topping them periodically with distilled water
    7- Low cost, replaceable electrolyte (easy to manufacture in the bush with ash)
    8- Proven, tested techniques for reconditioning in a residential garage shop
    9- Cost

    This last point needs a bit of explaining. This battery will nominally last 20 to 30 years. However, in some cases it may be opened up, cleaned up, and reconditioned to work for another 20+ years. Sounds a bit far fetched until you realize that there are batteries in use from around the time of WWII.

    This means that you buy it once. Lead batteries may with luck last 7 to 10-years. Lithium batteries about the same. Perhaps they may be lengthened to 15-years in some cases, but I doubt if this will happen in a hot climate.

    Therefore, lead and lithium batteries need to be replaced about two or three times to reach the nominal lifespan of a NiFe battery. This is sort of like the race between the hare and the tortoise. In the end, less glamour and a steady performance will win this race.

  37. Thank you.

  38. Hello Finn,
    Great article, really useful info. My situation is that I currently have a single phase supply and I have 32 PV panels on the roof with a Solax X-Hybrid inverter (5kW plus Solax Battery charger and 2 new LG Chem Resu 6.5 kWh batteries connected plus the Reposit Mgt system.
    We are changing to 3-phase power supply because we are putting in a new kitchen and the large free-standing stove my wife wanted requires a max 45amp supply – we were strongly recommended to change to 3 phase supply.
    I am guessing Configuration #3 would be my best option, which I assume would mean 2 new CT clamps for the Solax inverter and 2 new CT clamps for the Reposit system; unless I purchase a new 3-phase inverter and battery charger.
    Is there anything else I should be aware of in changing to 3 phase power with an existing system?

  39. Lawrence Coomber says

    Hi Eric.

    If what you said here is about sort of accurate: “after several years I would like to explore the possibility of adding a NiFe (Nickel-Iron) battery bank”…

    Then I recommend that you do nothing at the moment re: an efficient and contemporary energy plant design for your premises at the time.

    Even now it looks on the surface that you may have some other more cost effective and efficient energy plant deign options available, that will most certainly be more in focus with system design engineers moving forward.

    Talk with your system design engineer about this subject before you commit to your ideas is sound advice at this stage Eric.

    All the best for your energy project as you move forward.

    Lawrence Coomber

    • Hi Lawrence,

      I have some options that seem attractive; however, they are not ideal at the moment, and for this reason your advice is indeed ‘weighty.’

      I found a Fronius inverter, the Symo Hybrid. It is a 3-phase inverter which reduces the cost by requiring only one inverter rather than three inverters.

      It can be AC coupled to the line and DC coupled to the battery. It will supply simultaneously excess energy to the batteries in the event that the grid does down as well as house loads.

      In addition, it has an impressive energy management software to increase self consumption.

      The downside (not confirmed at this moment) is that it does not appear capable of working with NiFe batteries.

      The NiFe batteries are attractive since they would be on the left side of the battery chart (for cheaper storage costs per kWh) from this site.

      Finn has his bearings pointing in the right direction when he says that battery costs are still to expensive. I agree with him that they still need to drop further to the left on his chart.

      I am,also, keenly aware that nanotechnology, glass batteries, and ultra capacitor breakthroughs could be around the corner at any moment.

      The future promises exciting moments in our lives.



    • Thank you for sharing.



  40. Lawrence Coomber says

    Thanks Eric.

    And if passion for the subject amounts to anything (and it does) then you have that in spades, and we need more Eric’s contributing their ideas.

    Your learning will never be complete though: and I always recommend that people like yourself interested in exploring self-sufficiency options for powering their lifestyle (domestic, rural or commercial) going forward, get connected with an energy solutions design engineer early in the process rather than relying entirely on product and systems sales people. There is a difference in skill-sets at play and this difference is becoming more important as the industry demands more resilient, efficient, and smarter solutions moving forward.

    Best practice system designs focus on: Load Diversity, Specific Load Duty Cycles, PV/Battery DC Coupling and Charging Algorithm Controls, Battery Types and Chemistries, Energy System Smart Controls for example, and expecting that these fundamentals to be expertly implemented in and fully configurable in a single PCE unit is unrealistic.

    A case in point: your system concept so far:
    (1) Has stalled on your preferred battery type and chemistry (NiFe) with your chosen inverter type, without any solution available “out of the box” it seems, except to abandon your NiFe preference and go with something compatible (charging, discharging, battery management, battery input 150 – 400 VDC) with the inverter such as Fronius Solar Battery, LG Chem HV or BYD BBox HV.

    (2) DC coupled battery storage. Out of the box there is no battery “emergency backup” capability available through inverter configuration to do what you describe here: ”It will supply simultaneously excess energy to the batteries in the event that the grid does down as well as house loads.” This functionality will require a hardware addition/modification and has important strings attached also:

    (A) Only the designated “emergency circuits” will be supplied and these are separate (and relay-controlled circuits) to the “normal “main switchboard circuits;

    (B) Being a 3-phase unit, emergency backup controls are sensitive to phase current imbalance and managing this situation across the 3 phases for the “emergency circuits” is problematic;

    (C) Being a 3-phase unit implies rotating machinery circuits may be in use, and the inverter is sensitive to inrush currents with strict limits imposed before shutdown, this is also problematic.

    So just a couple of minor points of interest here Eric to illustrate my original suggestion that it is worthwhile discussing your ideas with an energy solutions design engineer, along with your preferred products sales person earlier in the system design process rather than later, to ensure your ideas are well represented or alternative concepts are brought to your attention.


    Lawrence Coomber

    PS. There are better battery storage options for you than NiFe now and looking forward.

    • Dear Lawrence,

      “And if passion for the subject amounts to anything (and it does) then you have that in spades, and we need more Eric’s contributing their ideas.”

      Thank you for your encouragement.

      My background is on the the business side of things. So learning the technical aspects of solar installations has become both a necessity (helping my kids to learn a different way of accomplishing daily things and lowering costs) and a challenge (wrong head for the physics and engineering involved in understanding solar and storage energy).

      Many years ago, I was fortunate enough to be blessed with two wonderful children, and when I stopped and looked around a bit I was concerned of the world I was leaving for them.

      I was contributing to consume things at a non sustainable rate, and smarter people than me were claiming that we had to change course, and worst of all I was teaching my kids to continue doing exactly same as their dad.

      For this reason, I sat down for a year, and I learned as much as I could to change my ways.

      In those days solar energy was still very expensive, but the one thing I could do was to lower my energy demand, and I did this with a vengeance by replacing inefficient water or electrical appliances with efficient appliances.

      This saved me money, and it reduced my level of energy consumption considerably.

      I, also, took the time to learn how to place things in my kitchen table that would both lower the number of trips required to go to the store and could be done sensibly at home.

      Both of these things (energy and food) have changed my approach to many things.

      What does this have to do with my children? Well I believe that you teach by example, and my kids learned along with their dad that two refrigerators that did the same thing consumed different amounts of electricity to do the same thing.

      We learned that a fresh loaf of bread made at home tastes different than a loaf of bread bought in a bag.

      We learned that efficient appliances require a much smaller solar system, and they require a much smaller battery bank.

      These little things really do add up. Today, if we needed, we could mange without space conditioning equipment, and our average daily energy consumption would amount to between seven to eight kilowatts per day without missing a thing on the use of modern lights or appliances.

      Our space air conditioning amounts to about 12-kilowatts of energy per day if left on 24-hours a day, and our production of energy could be accomplished with a 5-kW solar array both for house appliances and transportation (local driving).

      Twenty years ago I had no idea that this was possible, and my kids have learned along the way that their dad is sort of a solar nut.

      I will follow up on your solid advice for an energy system design engineer, but I still need to first find a battery bank for my project.



  41. Look at Configuration #3: 1 single-phase hybrid inverter with 3 x consumption CTs.
    I would suggest using 3x single-phase hybrid inverter each with single consumption CT. Single solar array supplying all 3 inverters. Each inverter has it’s own battery.

  42. Hi community,

    I found an interesting product when a low voltage battery is desired, but the inverter is not designed for them.

    If the inverter sends a high voltage to the batteries from the PV panels and the battery bank has a low voltage, a DC to DC converter is required.

    The DC to DC converter should take the high voltage from the inverter and convert this to a lower voltage.

    I am curious if the inverter could bulk, absorb, float, and equalize the battery bank.

    I am, also, curious if this product would be agnostic of whether the inverter is single phase or three phases.

    Anyone has experience with this product?



  43. Ross Chapman says

    Hello Finn,
    Great article, really useful info.

    Just realised that my recent post seems to be attached to other comments (probably hit the “Reply” button by mistake).

    My situation is that I currently have a single phase supply and I have 32 PV panels on the roof with a Solax X-Hybrid 5kW inverter (plus Solax Battery charger) and 2 new LG Chem Resu 6.5 kWh batteries connected plus the Reposit Mgt system.
    We are changing to 3-phase power supply because we are putting in a new kitchen and the large free-standing stove my wife wanted requires a max 45amp supply – we were strongly recommended to change to 3 phase supply.
    I am guessing Configuration #3 would be my best option, which I assume would mean 2 new CT clamps for the Solax inverter and 2 new CT clamps for the Reposit system; unless I purchase a new 3-phase inverter and battery charger.
    Having spoken to Reposit I now realise I need 2 new Reposit boxes (probably about $2000 installed) (and possibly 3 new ones as my current Reposit box is disconnected because it is sending out incorrect signals and thus running my inverter and Feed-in totally incorrectly).
    So, am I better off buying a new 3 phase inverter (probably around $3,000 to $4,000) and ditching Reposit, or buying the new Reposit boxes and letting them control the 3 phases and grid input and output?
    Is there anything else I should be aware of in changing to 3 phase power with an existing system?

  44. Brian Knight says

    A very helpful article which told me that configuration 5 is the appropriate one for us if we want to install batteries. We already have a 6.4 kWh solar panel system with a Fronius 3-phase inverter, necessary because our air-conditioning system is 3-phase. It did leave one question unanswered: what happens during a power cut? At present we have some power because Power Networks SA only shuts down one side of the grid. How do batteries handle this situation?

  45. Michael Oberhardt says

    I keep wondering why there isn’t a simpler option – available to any house with just a meter box / board upgrade

    Single phase house with solar, with an inverter with balanced 3 phase grid output. So you have your house and inverter and battery all on a single phase / circuit, but the grid output and input is balanced three phase. That way energy companies wouldn’t be worries by limiting output to keep phases balanced.

    • David Ritson says

      The problem is usually the other way around. Most houses only have a single phase connection.
      Slowly there are more options in or coming to market. As you say, it would be good to see better integrated, whole of system packages instead of the collection of components that may or may not even work together.

      It is something I intend to address, although it’ll be a few years to market yet.

      • Michael Oberhardt says

        I know most are single phase. But I’m saying with my idea, you would still need to get the powerline connection upgraded to 3 phase, but leave everything in the house single, so you aren’t trying to balance internal loads evenly across three phases (which in reality is impossible and inefficient). So the inverter (or a secondary inverter) handles the three phase export to and import from the grid, so when importing, it’d convert 3 phase to single. I mean the trick is the DC side, going in both directions, DC to single phase, DC to three phase, or 3 phase to DC to single phase

  46. Michael C says

    Hi Finn question on Tesla Powerwall 2, I know the units are single phase input, but in the event of a power outage can the unit power circuits on different phases.

    • Ronald Brakels says

      Hi Michael, Ronald here.

      The Powerwall 2 will only provide backup power to a single phase when the grid is down. They have updated their gateway box, but it apparently it still only allows backup on a single phase.

  47. Michael C says

    Thanks Ronald for your reply, the reason I ask is that in a few days I am having one installed as part of AGL VPP and I have 3 phase power. The contractors did a site inspection and looked at my board. All they said was I had to make room for their breakers as I am a qualified electrician I replaced the old style RCD’s with RCBO’s to free up some space. They said I can nominate any 3 circuits for backup, they did not say that they had to be on the same phase. So i’m a little confused, 2 of the 3 are on the same phase and 1 is on another. Im thinking is it their issue and they can sort it out as they have inspected the job or do I move the circuits around?

    • Ronald Brakels says

      I presume they will put everything that will be backed up on one phase. As this is a common thing to do when installing a battery system I expect they won’t have a problem. It probably wouldn’t hurt to double check to make sure both you and the installers are clear on what they are doing.

      But if you are concerned, since Finn has a Powerwall 2, I can check what he thinks tomorrow.

      • Michael C says

        Thanks Ronald I have a written quote that says 3 Phase integration so I might leave it as I have sent them pics of what I had done and they were happy with that. But still would be interested on Finns opinion

  48. Cam Muir says

    Hi Ronald,
    How would you determine if your solar microinverters are on one phase or split across the three phases. On my switchboard there is only one switch to isolate solar, so am I right in assuming it is only on 1 phase?

    • Ronald Brakels says

      That single switch may be the main switch for the inverter supply which, after that point, could potentially be connected to more than one phase depending on how it’s wired up. If you have documentation for the system it should tell you. Generally, if the system is small, it is usually only connected to one phase.

  49. I am having an additional system installed (fronius single phase inverter and tesla 2). This will run on a separate phase to my existing solax inverter.

    Does configuration 7 work with the CTs if you also have an existing inverter? (does that just connect to one of the other phases on your diagram?)

  50. michael Jj says

    I’ve pretty well thrown my hands in the air and given up at this point in time Finn.

    We installed an 8.7 kW (solaredge) system almost 2 years ago to complement our existing Rudd era 2 kW system.
    At the time I insisted that the size of the system required a 3 phase inverter but the installer told me I didn’t know what I was talking about. When the voltage continuously clipped the output and the single phase inverter shut down up to 20 times a day I fought for almost a year to get the installer to replace the inverter with the 3 phase inverter which was required.
    I also had to fight with Ausgrid for some time to reduce the street voltage as it routinely exceeded the maximum allowable.
    Its been an ordeal and a half but the system now works like a Rolls Royce on steroids. One step forward!

    I’ve been eyeing off batteries but as you routinely write ‘not worth it’. I agree.
    We’ll take the plunge eventually but I’ll need something which does not require an entire system rebuild or years of battling to fix what should have been done correctly in the first place .

    I was hoping you might be able to extend your analysis to cover my unique situation….which will become common place as households start putting in systems to cope blackouts and modern living standards.

    Hope you can weigh in on this one. Thanks

    • I empathise with you Michael. I installed at 15 kW SolarEdge system early this year. It’s an SE8000 8kW 3-phase inverter plus a SE500 5kW single phase hybrid (for a later battery). During summer we had a lot of drop outs – the voltage reported by SolarEdge was frequently over 255 volts and as high as 260! Not so bad during winter. I’m with United Energy. I made numerous calls to them and they did send out a team to monitor voltages, but I haven’t been able to find out the consequence of their data logging (after 3 phone calls!). They advised setting the cut-off voltage much higher on the inverter (I think it is now set as high as 255). Maybe that helped, don’t know. I await the summer sunshine with anticipation!

  51. Finn, thanks for this informative article – i watch your youtube video’s diligently.

    I have a 6.6kw LG system with enphase micro inverters. The house has three phase power. I’m having AGL install a Tesla Powerwall 2 with the new Gateway 2. I assume the best configuration for me would be configuration 15. I have the panels balanced over 3 phases with a Enphase 3 Phase Q Relay.

    AGL informed me that;-

    1. The battery can only be charged using 1 phase? Is this accurate? So as an example if my panels are generating 21kw of excess power – only 7kw will be used to charge the battery?

    2. Furthermore, they also informed me that during an outage my panels will not be able to charge the battery, is this accurate? I thought the battery would be charged using the single phase it is connected to.

    Is this accurate?

    In hindsight it may have have been batter for me to have all panels on the same phase.

    Your assistance is appreciated.

    • Ronald Brakels says

      Hi Guhan, Ronald here.

      I’m afraid that with your Enphase microinveters split between the 3 phases only one-third of your solar electricity will be available to charge the battery, as the Powerwall 2 can only charge from one phase. The best solution is likely to be to put all your solar on the phase the Powerwall 2 will be on. If you have over 5 kilowatts of inverter capacity then it will normally need to be export limited to 5 kilowatts.

      My understanding is, with solar on 3 phases the Powerwall 2 will not be able to charge the battery during a blackout because the solar system will have to shutdown to prevent electricity being sent into the grid on the phases the Powerwall isn’t on. Getting all your solar put on the Powerwall 2 phase will fix this problem.

      Hope this helps.

  52. HI Ronald, thanks for the prompt response – it was greatly appreciated. The Tesla Powerwall 2 has been active for well over a week.

    Tesla Charging over 3 Phases
    For the last week, the Tesla Powerwall has been able to charge at the same rate as the energy generated by the Solar panels over 3 phases. As an example – currenty the panels are generating 5.3kw over 3 phases, the house is using 0.5kw, the battery is charging at 4.8kw.

    I think this is due to the smarts in Tesla Gateway 2.

    Lets’s assume the Solar Panels are generating 1.4KW on each phase (4.2kw in total), and the battery is only connected to the red phase. The gateway monitors all phases and detects 1.4kw being exported on the white and blue phases – i.e. 2.8kw exported to the grid. The gateway gets the battery to draw down an additional 2.8kw from the grid on the red phase to offset the exports on the blue and white phases.

    The meter netts out the exports and imports across all phases at any given point of time.

    The reverse happens at night when i’m using a 3 phase device. As an example – say the device consumes a KW each on the red, blue and white phase. The battery exports 1kw on the red phase directly to the device and exports 2KW on the red phase to the grid. Thereby zero’ing exports and imports.

    Tesla Charging from the Solar Panels during a grid Outage.
    We had a two minute outage in the Adelaide eastern suburbs yesterday afternoon. The battery was able charge from the solar panels during this outage, I have a snapshot from the Tesla app with this scenario. I can’t explain how and why it worked.

    Thanks again.

  53. Hi all,
    Hoping to get some advice on connecting 2 Alpha ESS batteries into a my 3 phase system.
    System specs
    3phase fronius Symo 15
    3 x Strings of 12 modules on MPPT1
    3 strings of 12 modules on MPPT2

    I’ve been looking at configuration method #10 for Battery connection and wanted to ask if it’s possible to connect just 2 batteries, one to phase one and one to phase 2 without causing any issues?
    Why you may ask?
    There’s a good deal on down here in SA for the Alpha ESS batteries but I can’t stretch the budget far enough for 3.
    Id love to achieve blackout protection and charging during blackout, is this possible using this config?

    • Brian Knight says

      I have much the same question as Paul, a 6.5 kW 3-phase system using Jinko panels and a Fronius inverter. The 3-phase power is necessary to run our hefty air-conditioning installation. Getting straight answers to the questions around battery economics is proving extremely difficult, so I am looking forward to an expert reply to Paul’s post.

    • Ronald Brakels says

      Hi Paul, Ronald here.

      The Alpha ESS VPP is offering batteries at a particularly low price.

      As far as I am aware you can attach an Alpha ESS to two out of three phases. These systems will only be able to supply back up power if solar capacity is attached to their built in hybrid inverters and they will only be able to supply back up power to appliances on the phase they are on. If solar capacity is only attached to the Alpha ESS hybrid inverters then I believe they will be able to charge from the solar panels during a blackout.

  54. Lawrence Coomber says


    3 phase “hefty AC systems” can be good candidates to take off the grid and create a specific appliance/equipment off grid circuit for servicing this specific load.

    This can be a very economical and efficient design solution for those domestic/industrial/commercial scenarios where high demand electrical equipment(s) such as an irrigation pump or metal cutting press or hefty AC unit for example, set a high maximum demand tariff for the customer, but where those equipment’s duty cycle (largely daytime usage) is such that a standalone PV circuit plus controls, can reliably supply the equipment(s) load.

    This solution though requires experienced evaluation of the specific circumstances of the customer of course.

    Another example: A fish farm had a high dependency on many growing pond aerator motors equating to over 90% of a very high total annual electricity bill. The duty cycle of the aerator operations was daytime use only. The RE design solution was to take the aerators supply circuit off grid as well as installing process timing controls to ensure that a maximum of 4 aerator motors only ever ran at the same time, which reduced the system size due to a known and controlled maximum demand on that single supply circuit.

    The customer remained on grid but only to supply some very low demand loads (fridge freezer standard power circuit). The solution saved over $50,000 per annum in electricity costs and achieved a very low system ROI for the customer.

    Not all RE practitioners though have a working understanding of designing RE systems and including equipment duty cycle and circuit load diversity into their calculations.

    There may be something above though for you to consider Brian and have properly evaluated regarding your specific circumstances.

    Lawrence Coomber

  55. Coert van Calcar says

    This is a master piece of work, many thanks for that, the only piece that would make it 100% complete would be a matrix with the options. in the last part you give a series of best recommendations that are also covered in other scenarios that you highlight. if you would be able to complete your conclusion with such matrix it would help me, like

    Configuration 1-14 and then highlighting if it would support Y/N
    Consumption Battery 1 phase grid connected
    Consumption Battery 3 phase grid connected
    Consumption Battery 1 phase grid outage
    Consumption Battery 3 phase grid outage
    Battery Charging 1 phase grid outage
    Solar consumption 1 phase grid outage
    etc, etc

    the way I see it, only config 8 provides charging, solar consumption in grid outage (am i right ? )

  56. Jeff Lats says

    You said that people with 2 phase houses need to look at the issues as carefully as 3 phase houses. Rural NSW has a lot of 2 phase houses. I have 2 2.5kW SunnyBoy inverters connected to the net smartmeter, one on each phase of the 2 phases. When looking at batteries, it is a problem and there are next to no 2 phase batteries in the market and when talking to suppliers I am told that 3 phase batteries can’t be connected to 2 phase systems. As a layman it would seem that not connecting a phase would be similar to not consuming power on a phase.

    All the single phase battery examples in the article seem applicable to 2 phase systems.

    Is there any particular advice you can give on a 2 phase setup?

    • Finn Peacock says

      Simply add a single phase battery – the only issue can be getting permission to do this. If you have a single meter, then your battery can work with the other phase to self consume as if it was physically connected to the other phase (because the meter nets it out).

      If you have 2 meters then the battery can only self consume on the phase/meter it is attached to.

  57. Phil Schmidt says

    Hi,I have 20kw of panels and a 15kw 3 phase Fronius inverter.
    Since this thread was started in 2018 is there a way that I can make an apocalypse proof 3 phase battery system yet before the SA battery scheme is cut?

    • Ronald Brakels says

      Hi Phil

      I know one person who got a Fronius Symo 3 phase inverter with a BYD battery from NRG. Unfortunately, they haven’t given me the run down of how it works so I can’t give advice about it. But you may want to look into it and see if it’s suitable for you.

  58. Great article Finn

    when we installed the PW2 with a Fronius single phase inverter in a 3 phase house it wasn’t possible to have a 3 phase inverter as I don’t think there was one around at the time. A really simple solution we used was to put as many circuits on the solar linked phase in the switchboard as possible, and that means those circuits are backed up in a blackout as well. I think. We haven’t had a really long blackout yet to test

  59. Hi Finn,
    Thanks very good article. I have a single story 3 phase house which has a swimming pool and refrigerated central cooling system. I want to go with 10KW system with a hybrid inverter. As there are no 10KW 3 phase hybrid inverters available yet technician suggested 2 x 5kw Huawei hybrid inverters install as two seperate 5kw systems. What are the advantages and disadvantages of it? any other suggestions?

  60. Lawrence Coomber says

    Chuck learn more about grid tie solar systems and how grid tie inverters function.

    If you have 10 kW of solar PV you can exploit its full generation capacity potential by connecting it to one or more inverters totalling no less in overall rating of 10 kW. Inverters work at their most efficient at full power rating and can handle a moderate overload continuously also without any problems.

    Visualise the solar PV as a simply a day light available DC bus for you to exploit in first class modern power electrics circuits design, that you can hang any quality equipment off.

    If you have a 3 phase mains supply, you can connect both 3 phase and single phase inverters powered by the DC bus to the grid.

    Adding a variable frequency drive water pump if useful is fine also. A fully isolated stand alone battery bank solution for independent services circuits in event of a blackout can be a good design addition. You can install up to 90 kW of fully isolated standalone solar solution at your premises in addition to your 10 kW grid tied system for example if you want, which can be a very efficient design depending on a customers individual circumstances. Very common in commercial factory situations. Talk with your electrician.

    It’s your call within best practice design limits and standards and regulations. Only you know what you want to achieve, and what level of extensibility you want moving forward.

    Talk with your electrician is best though, and be clear on what it is you want to achieve from your solar; don’t be tempted to solve all the design options yourself though, there is a lot more that can be achieved with Solar PV solutions designs than we are currently seeing offered.

    Lawrence Coomber

  61. Have a three phase system, and about to install a GW10KL-ET inverter connected to a 10kw solar bank.. but before i sign up, need to ask has anyone out there installed one of these inverters? and if so, have you connected any batteries to your system? if so, what type? I am looking at getting 8 tesla battery car modules to reach the minimum voltage of 180v – also giving me 40kw of storages..

  62. Lawrence Coomber says


    Have you read and understand the manufacturers specification?

    The GW10KL-ET is a compliant On-Grid Inverter and it needs the grid to function. There is a backup option meaning it will supply selected circuits in time of blackout, but you need to fully understand the battery connectivity requirements to move forward safely and with compliance Dominic.

    Read the Inverter Specification (20 pages) and learn about the DC battery source power limits and requirements. Particularly maximum charge and discharge parameters. Assuming 192 (say 200 V) Battery Source and maximum allowed DC current of 25 A; well you can do the easy maths mate regarding battery capacity.

    You are in the grey zone already by not opting for a BESS. And compliance will be an issue for you to connect this proposed system integration to the grid. Also, AS3000 will have something to say about compliance and the Electrical Safety Office will have a close look at the installing electrician involved based on this proposal.

    Good luck moving your design forward Dominic, but you don’t sound to confident about it all, and safety, functionality and compliance will all jointly be your biggest headache.

    Lawrence Coomber

  63. we have recently been quoted on a system that claims to provided 3 phase with ups / backup off grid capability using a Goodwe ET Series inverter. so has the technology overtaken this article from 2018 ? Or am i being optimistic thinking the product can deliver on its claims ?

    • Ronald Brakels says

      Hi Daryl, the Goodwe ET series of 3 phase inverters came out a few months after this article was written. Goodwe are lower cost but reliable inverters and I certain it will meet its specifications, so I presume it can deliver on the claims. But it is important to be clear on just what it can and can’t do, as there are definite limitations on the amount of backup power any hybrid inverter can provide.

      Update: That should be “…it was announced a few months after this article was written.”

      • good to know – we arent looking to host a party in a blackout but we do want to keep the fridge , freezer and water pumps running when the grid is down for a few days (as has happened in our area) . What would be the critical question to ask ?

    • Finn Peacock says

      Yes – finally there is a 3 phase hybrid inverter that appears to do everything – I’ll be publishing a deeper look into the ET series soon…

      • hopefully very soon 🙂

      • Michael B says

        Any update of the Goodwe ET series review? I’m really interested in it, particularly the unbalanced output which is a bigger deal over here in NZ where we dont get the advantage of summed metering over the phases like you guys do.

        If the ET can do unbalanced output WITHOUT requiring a battery it sounds like a great option for us 3 phase kiwis 🙂

  64. Stuart Evans says

    Hi Finn/Ron. You might like tochange ‘solar inverter’ to ‘battery inverter’ for configuration # 12.

  65. Hi Finn,

    Please make the following changes to Configuration #1:


    * It is expensive. There are only two-three-phase hybrid inverters currently on sale in Australia. A 5kW Fronius Symo Hybrid retails at about $4,000 just for the inverter3, and a SolaX X3-HYBRID-5.0T costs just over $3,000.
    -> Sungrow SH5.0/6.0/10 RT 3 phase hybrid inverters costing around $3000 is also now available.

    Can’t be done for AC coupled systems like the Tesla Powerwall 2 or Enphase batteries. This is for DC coupled batteries only. And the batteries must be compatible with the specific inverter model. Above Sungrow hybrid inverters are compatible with LG CHEM RESU 10H.

    I know this as I did a bit of ground work for my needs and I am getting this combination.


    • Ronald Brakels says

      There is now a little more choice for 3 phase hybrid inverters in addition to Fronius and Sungrow. At the lower end of the market Growatt have a 3 phase hybrid inverter. Huawei has one, although their inverters are generally not capable of providing backup power. And the SolarEdge 3 phase AUB hybrid inverter will hopefully be available in December.

  66. Currently looking at a solar system and would like to connect a battery in the future and so want a system that would facilitate this. The house is 3P and I am offered a 3P inverter in one quote and a 1P inverter in the other. My hardware preference was for a Fronius inverter and HV battery (Tesla).

    For the 1P inverter I can see how diagram 7 fits and power in/out is balanced for a net neutral cost. In an outage I believe the inverter shuts down as there isn’t 240V across all phases and the battery can’t supply power to the house – true?

    I believe that it is preferred to have a 3P inverter with a 3P house but I don’t see a diagram including a Tesla battery that covers this option (is there a new diagram ??) Also heard that the Tesla battery can’t work across 3 phases at present (fact or fiction?)

    Should I be considering other options eg LG battery? Love some feedback

    • David Ritson says

      If I were to be buying now, I’d have a close look at the Sungrow hybrid 3-phase inverters and pairing it with the BYD HVS or HVM series batteries.

      With that inverter you get the works on 3-phase including full backup with no interruption. For me the only question is whether 10kW is enough to run some bits of machinery in my workshop. Which I don’t have to use if the grid was down, so likely a yes.

  67. Lawrence Coomber says


    PV modules are cost effective so why not install another 5+ kW of PV plus 1/3 phase inverter as a Stand Alone System design, which will also entitle you to STCs for this separate and additional install.

    System[s] separation is critical though, and achieved through a separate Stand Alone System MSB (including separate MEN and other factors that must be considered) and single circuit MCB load circuit wiring for example; in your case possibly servicing another CB distribution board in your workshop.

    With appropriate Solar PV Array controls design in place, PV Array reconfiguration (whilst maintaining system separation) can also be beneficial for individual customers needs.

    Domestic like Commercial and Industrial RE Power Solutions design, is broad ranging and very versatile in the hands of experienced professionals, and will depend entirely on the customer’s requirements, and importantly the circuit/equipment duty cycle and demand [and duty cycle management controls] required for individual or collective load circuits.

    Single and multiphase solutions, and similarly, Grid Tie and Standalone Systems alike (plus storage or VFD perhaps also) can be properly dealt with in robust and reliable compliant RE system(s) design, to give you precisely what you want moving forward.

    Talk with your local RE engineer for a detailed heads up on these points David.

    Lawrence Coomber

    • David Ritson says

      Agreed. Lots of options with configuration. Just not many options with bigger hybrid inverters. If there was bigger units available I’d be on them. But there is a big gap in the market between 10 and 50kW.
      And yes, also thinking of VFD’s for my lathe and mill, both have 10hp motors. The 300Amp welder is another matter. Not sure how well that will play with an off-grid inverter…….
      But like I said, if the grid is down I can find something else to do. The grid is pretty reliable here anyway.

  68. Lawrence Coomber says


    My comments were not referring to a hybrid system, rather dual power systems isolated and operating independently of each other at the one premises, with one being an Off Grid system and the other being an On Grid system, which constitutes power systems compliance satisfying both the network regulations and the Clean Energy Act regulations regarding STC’s eligibility.

    There are high quality CEC listed approved Stand Alone inverters (10-100 kW: 1 phase < 30 kW – 3 phase 30-100 kW) which cover the full range up to the CER limit for STC's of 100 kW. Over 100 kW systems leave the STC domain and move into LGC's.

    Regarding the 300A welder. This is easily (and cost effectively) accommodated in Stand Alone designs via battery storage, and the system designer having experience in designing systems/controls suitable for specific high demand equipment's/circuits based on daily Duty Cycle.

    Lawrence Coomber

  69. David Ritson says

    Yes there is a range of stand alone inverters.
    Show me a range of mid size (10-30kW) hybrid inverters though! Preferably ones that can change over between grid / off-grid without interruption.

  70. Lawrence Coomber says


    Often not commercially viable for manufacturers to invest in certification for use in AU for this hybrid type model you describe. Network regulations and broader compliance issues such as (isolation and controls) are keypoints, and being a small market determines what products manufacturers will see as commercially viable here.

    A quality design 30 kW hybrid inverter similar to what you describe that I have experience with, is popular in some parts of rural California for over 3 years now.

    Lawrence Coomber

  71. Priscilla Fiedler says

    I have 3 phase set up at home. Built this way just in case i ever decided to get a pool installed or a spa etc. I wanted options. I have 2 x SMA Sunnyboy inverters each on their own phase and a 5kW system set up of solar panels. I am about to purchase a Tesla Powerwall 2 with the install date set for 12 days time.

    Western Power have just sent me this info with my application approval. “This approval expires on 29/06/2021 

    Please read the important conditions applying to this approval.
    Your electricity retailer will update your meter – please contact them for more information.
    We may inspect your system to ensure compliance with the conditions of approval.

    Special operating conditions
    • As at 14 Feb. 2020, the Tesla single phase AC Powerwall 5kVA battery/inverter when installed on a three phase connection is not compliant with Western Power’s balancing requirements. To address this non-compliance, Tesla has implemented software changes that limit the charging/discharging capability of the AC Powerwall inverter to 3kVA on three phase connections. Your application is approved on the condition that the AC Powerwall inverter is software limited to 3kVA and time-based operation is implemented.
    • Battery inverter is not to generate between the hours 10:00 to 15:00 inclusive.”

    Can you please advise what I should be advising my installer or western Power? I have zero knowledge in this space but feel for a $16k unit I need to maximise storage and use. Long term plan is to get a Tesla Car.

    • Ronald Brakels says

      This means your Powerwall won’t be able to supply your home with power from its batteries during the day from 10:00am to 3:00pm. On sunny days this may not be a major problem as your solar system may be able to meet most of your home’s consumption, but it will be a problem on cloudy days and when your home’s power consumption is high. If there is usually no one at home during the day this is less of an issue. It will be able to charge its batteries during the day.

      When your Powerwall is allowed to supply power, instead of providing up to 5 kilowatts of power it will only be able to supply 3 kilowatts. For a typical household this is not a disaster as power consumption is usually below 3 kilowatts, but it does mean you will use the Powerwall at least a little less and so its return will be less.

      My advice is to only go ahead if you are happy with these limitations and understand they will make it even more difficult for the Powerwall to pay for itself. You may decide you’d prefer to save your money and put it towards the Tesla car and I expect there will be more cost effective battery options in the future. But if you’re not worried about the financial return, then you’ll still be able to get a lot of use out of the Powerwall despite the limitations placed on it and I presume and hope that in a blackout it will be permitted to provide a full 5 kilowatts of power.

      • Priscilla fiedler says

        Thank you. I work during the day most of the time so that time limitation isn’t too bad. Although for now am able to work from home two days a week. As with anything during covid times that can change at any time. The house is predominately just 1 adult and on occasion my adult son is with me on R&R so we don’t draw a large load. Fortunately perth is mainly sunny days.
        The return isn’t of high concern either. My biggest concern is no aircon during blackout as it’s spread over all 3 phases.

    • A different solution could be a flywheel and ultra capacitors working together.

      A bit more expensive upfront, but you buy them once, and you never buy them again.

      They provide plenty of life cycles with little degradation, and modern flywheels are basically maintenance free since there is very little friction due to magnets.

      Response time of capacitors is not too shabby with the ability to absorb or provide large rush of energy at once thus acting like a buffer between loads and flywheel(s).

  72. Michael Paine says

    I have single phase power, a Powerwall 2 and a swimming pool heat pump. Looking at my usage, I wouldn’t expect the Western Power conditions would affect my situation significantly.
    I would rarely exceed 3kW consumption from the Powerwall and, of course, (expensive) grid power is always available to cover excessive consumption. During a blackout I turn off high consumption devices to conserve power for the fridge etc.
    I rarely draw significant power from the Powerwall during the middle of the day, including cloudy days. Most of the time it is used for powering devices during the evening when peak rates apply in Sydney (2pm to 8pm in summer).
    I have noticed that the Powerwall sometimes charges itself from off-peak electricity at night – It seems Tesla are trying to predict cloudy days ahead but have some way to go.

  73. Matthew says

    There are also 3 phase hybrid inverters from MPP Solar. Running 2 of them and works well.

  74. David hukin says

    My spouse runs a small business from home, so I am looking to add a battery solution that includes full backup of all phases during a grid outage. The ability to charge the battery from the solar panels during a grid-outage would be nice too.

    I currently have a 6.6kw of solar panels with a Fronius Symo5 3-phase inverter. Although I noted the advice about 3-phase inverters before installing, unfortunately the WA regulator no longer allows single phase inverters to be fitted to a 3-phase supply – “Any application for a single-phase inverter on a 3-phase supply over 3 kVA will not be approved as the voltage rise on the service lead will exceed 1%.” ref:

    It seems like the best option is #8: Three-phase battery inverter with a three-phase solar inverter. Unfortunately, from what I can see, Three-phase battery inverters are crazy prices. I know I should have done this at the same time as the initial solar install in late 2020, but I balked at the price. Now I am retrofitting a battery and it will be far more expensive than if I had done it all at once. An own goal.

    Can anyone recommend a good 3-phase battery inverter? Alternatively, are there any newer or creative solutions that have arisen since this article was published?

  75. Michael B says

    With config 1 (or config 8 for that matter), when the battery is discharging does it discharge evenly across the 3 phases?

    i.e. If there is only 1kW of load on one phase does the battery just discharge that 1kW? Or does it have to discharge 1kW on each of the 3 phases so 1kW being consumed and 2kW will be going back to the grid?

  76. Lawrence Coomber says

    Michael B:- [Ref: Battery Storage]

    A discharging battery storage is a simple DC power source supplying DC current to a connected LOAD.

    Battery storage is configured to have 2 wires only as an Output. One being denoted Positive and the other one Negative. Battery storage can only ever exist in one of two states: (1) Charging or; (2) Discharging.

    Don’t get confused by Batteries, they supply (discharging) or consume (charging) DC current only in a circuit [or network of circuits] and have no relationship to AC phasing of the connected load (Inverter) whatsoever

    In your case that connected load is simply an Inverter or PCE. The Inverter or PCE AC Output specification is totally irrelevant to the battery. Whether a 1 Phase or multi phase Inverter or PCE is also irrelevant.

    Learn more about Kirchhoff’s Laws. They are immutable and accurate for all DC circuits.

    Lawrence Coomber

    • Michael B says

      Hi Lawrence,

      Not really what I was asking. I understand what batteries are and how they work, my question is more about the typical behavior of 3 phase hybrid inverters. I’ll rephrase my question….

      If a battery (simple DC power source) is discharging to a 3phase hybrid inverter (connected load), does the inverter treat it just as it would DC coming from a solar array and convert it to AC over 3 phases (i.e taking 3kW from the battery to cover a 1kW load on 1 phase, with the other 2kW going back to the grid on the unloaded phases)?

      My assumption is that it would.

  77. Lawrence Coomber says

    Michael B:

    Your assumption is wrong.

    What you have described is how a typical Off Grid Standalone Inverter functions which does not differentiate between whatever the DC source [or combined DC sources] input is {example: Battery, Solar PV, Rectified Wind Generator, Rectified Pico Hydro Generator, Rectified Genset etc; as long as the Inverter DC Input Voltage is within the Inverter DC Input Voltage specified low/high limits.

    When the Grid is involved though as in your case; there are network and other Government Authorities regulations that the customer must legally abide by regarding embedded generation systems connected to the network, or be prosecuted.

    The regulation that applies to your question is that embedded generation systems that include a battery must include intrinsic controls that prevent battery generated power from be discharged to the grid.

    These controls functions are in-built into the On Grid Inverter design functionality and need to be to obtain CEC approved inverter approval.

    Lawrence Coomber

    • Michael B says


      So if I boil down what you are trying to say…

      – An Off Grid Standalone Inverter doesnt care if the DC input is battery or PV and will split AC output evenly across 3 phases. So in my example of a 1kW load on a single phase the inverter would draw 3kW DC from the battery and output 1kW+1kW+kW (1kW AC going to the load, 2kw AC going to some kind of dummy load since there is no grid)

      – A Grid Connected Hybrid Inverter is not allowed by regulation to take DC input from a battery and export it to grid. So the battery draw from the inverter could only ever total the lowest load from each of the phases, multiplied by 3. And in my example that would mean that there would be no draw from the battery at all (0kW x 3 = 0kW).

      I dont understand why there would be legislation preventing battery stored power being discharged to the grid when solar has no such issue, but if thats the case so be it.

  78. Lawrence Coomber says

    Michael B:

    Passion for any subject means everything in my book, and I admire your obvious interest.

    1. In your previous posting though, your assumptions [Off Grid Standalone PV/Battery 3 Phase Inverter System Functionality] and [On Grid Hybrid Inverter System Functionality] are both wrong:-

    A. Modern 3 Phase Inverters don’t ‘split AC power across phases’. There is no such power electrical technology concept in play. All 3 Phase Inverters accept a DC Power Source Input and according to the Inverter DC-AC Conversion Circuit Topology – produce a 3 Phase near sinusoidal AC Output up to [or nearly] the power capacity of the DC Input Power Source at any given time. This functionality will continue un-interrupted whilst the DC Input Parameters specified for the Inverter are maintained.

    B. What determines the AC Output (Current and Voltage – for each phase) is the size of load; type of load; and power factor of each load connected to each phase. Loads can be many and varied types and parameters; such as variable impedance; power quality; and power factor:- for example, varying types of resistive loads connected to any/all of the three phases; or motor loads; either single phase or multiple phase motors, etc.

    C. Your 1 kw load example connected to 1 phase of the 3 phase inverter output is exactly that:- a total of 1 kw load on the inverter output – no more no less. If there are no loads connected to the other 2 phases, then there is 0 kw output on those 2 phases. There is no such concept of ‘dummy load’ as you have mentioned.

    D. Your example though Michael does raise an important 3 phase connected loads concept, and that is the subject of Balanced or Unbalanced 3 Phase Loads. It is a very important topic for power electrics circuits designers, and best practice for system owners is to minimise Phase Unbalance to less than around 4 percent to maintain high system efficiency; and manage IR losses; power quality; and voltage and current stability.

    E. A reasonable approach to your example 1 kw load circuit [if practical] might be to rewire the load circuit into 3 circuits of roughly equal load value to ensure the inverter operates at maximum efficiency with minimal losses.

    Note on Battery Charging and PV Systems:

    Battery Storage charging is a simple concept Michael and can be easily integrated into any RE System Design in a number of ways, but the same key point will always apply whether charging is by a PV-DC Coupled Charging Circuit [typical Off Grid Standalone design] or a GRID-AC-DC Coupled Charging Circuit; and that is the charging circuit will include IC controls, that prevent over-charging the battery storage stack, and manage the charging algorithm as defined by the particular battery stack designer/manufacturer.

    Lawrence Coomber

  79. Michael B says

    Hi again Lawrence, I appreciate your replies.

    My statements are queries not assertions, and you say they are wrong (which they likely are), but you then dive into technical details and terminological nuances without appearing to answering the root question.

    I am really just trying to determine how the battery on a typical (balanced output) 3 phase hybrid inverter behaves when presented with a phase-unbalanced load.

    I think I’ll have to quit here and assume my question is either nonsensical or beyond my ability to explain 🙂 Or perhaps another reader can decipher what I am trying to ask…..

    Oh, I’ve found a diagram which shows how the unbalanced output works on some inverters.

  80. Richard Allan says

    Hi Guys
    Have a rural property with single phase power
    About to do some renos and extensions and also plan for a couple of cabins for rental accommodation.
    I believe we will need to upgrade the incoming power supply with the load we will use or spend money on solar + batteries and kinda be off grid but with grid supply for charging when the suns not out or we have consumed too much and batteries getting low.
    I would also like to have the ability for charging EV’s for the cabin guests.
    The cabins will be 200 or 300meters apart and away from the main house so may need to charge a car closer to the power source rather than at the cabins.
    I believe this should be three phase to charge the cars otherwise it takes a very long time on single phase and a car in one charge could take 40 to 80kwh in one charge as this will be a holiday destination after a bit of a road trip!

    So is the above scenario achievable with high peak loads for a house with three families using it for holiday accommodation plus two or three other rental cabins with a 3 phase off-grid system for car charging with the single phase grid supply as a backup?

    Or do I just go with single phase car charging?


    • Lawrence Coomber says

      Hello Richard – you certainly do have options.

      1. You are heading down the right track with your thinking, but you need a bit of tweaking to be able to fully visualise the functional parameters and concepts to achieve an optimum design solution to fully satisfy your specified requirements.

      2. Maintain your current Grid Service as is. It does not need any capacity upgrade. And revise how you see the Grid supply moving forward from the Main Supply Source [which it currently is]; to a Secondary Supply Source [which it should and can become quite easily and cost effectively].

      Your System Solution will end up something like this: –

      3. Install a single ground mount [or SS wire mounted] Solar PV Array as DC Power Source [1] to create an Off Grid DC Bus. This DC Bus should be visualised as the ”backbone” of your Standalone Power System which can seamlessly have any other DC Power Sources easily and simply added as required, and at any time or capacity, from other power sources such as: – batteries and/or ultra-capacitors in combination as a DC storage stack; small opportunistic wind power source [DC]; pico scale hydro power source [DC] if the key requirements for pico hydro can be exploited at the premises; etc.

      4. The DC Bus is then able to simply and effectively have any number and type of Power Conversion Equipment connected to it, and be reticulated around the premises as required to supply all of the premises specific load circuits; for example in your rural situation: – VFD’s for irrigation management and general water services pumping; 3 phase Off Grid inverters for 3 phase machinery and equipment as required [including Car Chargers]; single phase Off Grid inverters for general domestic supply and lighting services. Etc.

      5. The critical first step in your decision making though is a site inspection by an experienced Standalone Power System Design Engineer who can quickly identify the key design criteria for your property and ongoing requirements.

      6. Learning about Load Diversity and Control Logic for Smart Integrated Off Grid Power Solutions Design would be a good start for you as you go forward Richard. Understanding Load Diversity is the single most important design consideration for power engineers involved with modern cost efficient SPS solutions.

      7. It is a good time to be thinking about cost effective SPS power systems designs particularly for rural applications, and also energy intensive farming applications. PV costs are low and STC’s are available for SPS systems up to 100 kW capacity on any rural or domestic premises.

      8. All the best as you move forward with your project Richard and if you need any advice at all contact me at any time.

      Lawrence Coomber – Power Systems Engineer [CEC Licence: A8765474]

      • Richard Allan says

        thanx for the info Lawerance and great to know my thinking is on the right track, with my very limited knowledge.
        1. Why would you suggest a single ground mount Solar PV Array?
        We need to build a shed so I assume this will be sufficient and we have the ability to orientate in the best possible direction.

        2. I dont currently understand some of your terminology but great to have these words for some research 🙂

        3. Yes there is a couple of creeks although not much fall, so something Hydro to contribute will give me something to think about, although while these creeks may only be about 200mm deep, I have seen debris in the trees about 4m higher than the river from March flooding so it could be costly to see that get washed down the river ever decade with big rain events!

        4. We wont have to much in the way of energy intensive farming applications, its the humans that come and go will be the biggest users!

        5. the idea of adding as we go is very appealing to use just enough cash on the initial setup upfront then more components as we develop our plans over 2 or 3 years

        • Lawrence Coomber says

          Hi Richard.

          1. A Rural property Off Grid Solar array should always be a ground mount design given sufficient available area.

          In your case you mentioned distances of 200/300 metres so your property appears to be a good candidate for a ground mount array. Ground mount designs are more robust; less costly; and more extensible than roof mount designs.

          Importanly a ground mount array can offer a dual use structure design option for other Off Grid system equipment e.g Storage and PCE.

          2. Regarding Pico Hydro generation, the first thing an Off Grid Power Solutions Engineer will evaluate at a rural site survey, will be its potential to exploit gravity through the availability of a reliable permanent water resource (spring, stream, river). Flooding and rising/falling water levels are of no consequence to small scale Pico Hydro designs that rise and fall with changing flows.

          3. Having a water resource on your property opens doors for you to quantify and think more about Richard. For example a simple V notch weir introduced into a low flow rate/capacity watercourse or stream can provide useful power 24/7 to charge a storage battery stack for example.

          4. Please keep us inforned as you progress your important project Richard.

          Lawrence Coomber

          • David Ritson says

            With all due respect Lawrence, I’m going to disagree with your point 1.

            Just because a rural property may have plenty of area to spare for a ground mounted solar PV array doesn’t automatically mean that should be what is done.

            Easily the most cost effective and sensible option is to mount it on a rooftop. Especially, as in this instance, the building can be sited and oriented to suit the array. With a bit of forethought and planning the shed structure can be made to suit supporting the array. The mounting rails are little more than an mechanical adapter. As opposed to a ground mount system where an entire purpose built structure is also required.
            Plus the added benefit of “dual purposing” that roof area, reduced temperatures in the shed, and likely to be on top of the system hub – less cabling.

            And any decent rural shed could easily accommodate 50kW or more of solar. Far less likely to have the constraints of complex house roof shapes.

  81. Hello.
    I have enphase gridtie microinverter system(3phase). I would like do add some battary but I’m not shore is it working? Enphase battary is unavailable in my country. What would you suggest?

  82. Andrew McDonald says

    Hi Finn,
    Thank you for this brilliant article. I learned heaps. Regarding system number eight, is is possible to connect an ten-year old 3Ph 5kW solar inverter in parallel with a new 8kW 3Ph inverter to feed this battery system?
    Many thanks in advance.

    • Ronald Brakels says

      Hi Andrew.

      If you have an existing solar system with a 5 kilowatt inverter you can leave it as it is and install a new 8 kilowatt 3 phase hybrid inverter with a battery. You battery will charge when your new inverter detects the home is exporting excess solar power to the grid, so your old solar system will be able to contribute to feeding the battery. But since your existing solar system is so old, you may want to consider removing it and installing an even larger new solar system.

  83. Andrew McDonald says

    Hi Ronald.
    Thank you for your reply. It was very helpful.
    Best wishes for 2022.

  84. Ashley Garnett says

    Great article, really helped me understand how solar, three phase and backup solutions work.

    I’ve got three phase with 15kw of microinverter capacity spread across the three phases (17.8kw solar system – 43*Maxeon 5 panels).

    I’m planning on getting a Powerwall 2 to minimise grid use overnight. If I got an additional two Powerwalls, I could back up all three phases and utilise my entire solar system in the event of an outage rather than just go down to the power produced on the battery’s phase. The main reason would be to utilise my full solar production capacity in the event of the grid going down and to allow 3-phase car charging to continue during this outage.

    To do this, do I need 3 Tesla Gateways or is one Gateway 2 able to coordinate all this?

  85. Peter Sie says

    I have read all of your comments and I do believe that someone out there might be able to offer me a bit of constructive advice.

    How I should configure the perfect off- grid three phase plant using 6 x LG RESU16L batteries? What I need to know is what you would recommend is my best matching DC coupled to a 15kW+ 3 phase standalone inverter?

    I have not decided how to size my Solar PV capacity, but I might add that my power use involves:

    • Charging a Tesla X Plaid EV (75kWh battery) on a regular basis.
    • Running a MXZ-5E100VAD – 3 head/10.0 kW air conditioner.
    • Heating water using a Rheem 410 L twin element water heater.
    • Using a Samsung QB98R 98″ 4K UHD 24/7 TV Commercial Display.
    • Running appliances in a standard kitchen (oven, cooktop, micro wave oven etc).
    • Operating 20 Roller Shutters.

    I am planning to build very soon a new 1 storey Dwelling and is therefore unable to offer any useful historical electricity use data. I need plenty of power ALWAYS and think I need to get close to 100 kWh battery capacity (96kWh).

    I have eliminated my first choice of battery (performance and software are perfect) which is Tesla’s Power Wall 2 because the production backlog is in excess of 90,000 batteries and Power Wall 3 is not yet announced, there is a long wait.

    My second choice is RedFlow’s Gen3 battery, however, I have not yet met a dealer who has enough experience with installing them.

    My third choice is therefore 6 x LG RESU16L Prime which currently can be purchased for $86,580. Hope someone can help me to design the perfect configuration for me.

    • David Ritson says

      There is a gaping gap in the market for 3-phase hybrid inverters over 10kW.
      This would fit the bill easily:-
      50kW is more than necessary but would allow you to install plenty of surplus solar, and it would have the punch to start larger electric motors etc (a reason I’m looking at it). The battery capacity can be varied when you order it.
      So who is going to be brave enough to order one of these?

    • Lawrence Coomber says


      You certainly do have options for a fully featured 24/7 standalone power plant solution, but as is always the case, the devil is in the detail.

      You need to take a breather though and seek professional advice before proceeding.

      The details you have discussed as is, do not guide anyone to instantly ‘hang their hat’ on a world’s best practice system design to suit your circumstances.

      Yes: advice for high reliability and fully functional 24/7 Off Grid systems design, based on genuine experience in this space, is not easy to find.

      The Australian Off Grid engineering industry is light on contemporary skills and experience, particularly in higher voltage integrated systems, and equipment manufacturers are not in the business of acting as systems integrators of other manufacturers complex technology; but high reliability equipment integration is ultimately what a long life and fit for purpose system design is all about.

      The design outcome though starts with an in depth site survey; and from that, an experienced off grid solutions engineer can systematically move forward with design options.

      A Site Survey is not a critical requirement for On Grid Solutions but the reverse is true for Off Grid Solutions: in fact, it is so important for Off Grid accreditation and licencing for future Renewable Energy Apprentices and Engineers: a new Skill Training Unit specifically dealing with Off Grid Site Survey Engineering Skills Training, has been included in the new 2023 National Electro Engineering Training Syllabus.

      I am a member of the Government RE Technical Advisory Committee that has just finalised the new National RE Training Syllabus; and the Off Grid Site Survey Unit was considered by the committee to be one of the most important new skills training units to be included in the overall training package for apprentices and engineers wanting to operate in the Off Grid industry.

      Back to some of your dot points:

      1. The information listed does not translate at all towards an Off Grid Solution being reliably worked towards.

      2. One point being that you have not described anything about the location and the premises and property characteristics. This is critically important. From this site survey, all things downstream unfold and evolve.

      3. You have misinterpreted the term DC Coupling in this scenario. A Standalone Solution incorporating Solar PV and Battery Storage [both DC power sources] are by definition DC Coupled [via appropriate software controlled monitoring and control hardware devices]. Standalone DC/AC Inverter’s; Variable Frequency Motor Drives; and other DC Input equipment as required will be connected [via controls] to the Solar PV and Battery Storage DC sources [one or more DC Bus].

      4. $86,580 [just for PCE and Battery Storage] makes no commercial sense at all for a small scale Standalone system [<30 kW] and you should definitely seek alternative advice.

      All the best for your project Peter and carefully work through it step by step.

      Lawrence Coomber

      • Peter Sie says


        Your comments are highly valued Lawrence. Unfortunately, my IT senior management background is not helping me here and I began with a misinterpretation, not good. Site survey. Of course, site and building characteristics are important, so let me open that door.

        205 sqm single storey dwelling with flat roof on 10 acres+. Site is slightly south of Newcastle. Building designed by me will be built in 280 mm ZEGO FireFORMS (100 mm polystyrene on the outside, 120 mm steel reinforced concrete at the core and 60 mm polystyrene on the inside). Flat roof design using ZEGO’s ZlabFORMS (again highly insulated). Double glazing doors and windows with BAL-40 roller shutters. The dwelling cannot burn and is highly insulated.

        I am open to alternative battery brands and capacities. My first choice of battery (performance and software are near perfect), is Tesla’s Power Wall 2, but because the production backlog is in excess of 80,000 batteries and Power Wall 3 is not yet announced, there is a long wait, so I move down my list.

        My second choice is RedFlow’s Gen3 battery, however, I have not yet met a dealer who has enough experience with installing them and their marketing people are not interested in discussing potential orders. It appears to me that RedFlow is not production scale ready.

        This is why I elected the LG batteries, but I am open to other brands provided I get a good match between Solar PV, Inverters and battery efficiency.

        I forgot to mention on the consumption side, that I also should include a washing machine and a dishwasher.

        I will try to reconsider my battery capacity, but essentially, I want as an off-grid person to have power at all times, and I could cut down on my battery capacity by taking my Tesla car recharging elsewhere, which I am a bit reluctant to do.

        Peter Sie.

  86. Lawrence Coomber says

    Thank you Peter:

    Your update illustrates perfectly what I emphasised in my earlier post about the critical importance of a professional site survey, and how engaging an experienced Off Grid Solutions engineer/integrator at the project outset, might reveal system design opportunities not possible to be envisaged at all without a professional survey.

    Here is a 2021 Rural Off Grid case study conducted in Southern Qld that amplifies this point: –

    1. The site survey comprised two bare bush rural blocks adjoining each other, bordering the Condamine River totalling [12 + 7 = 12 acres], along with a brief to design an Off Grid Solution for these properties for their development with dormitory style Air B&B cabins to accommodate weekend fossickers around the local 1880’s era gold fields.

    2. The larger block is lightly bushed flat land with 150 meters of river-bank frontage about 14 metres above the river. The smaller block is a very deep ravine 200 meters long scoured over the centuries as a watercourse from the surrounding hills at 90 degrees to the river. The high point of the ravine is 30 meters above the river.

    3. Searching historical records revealed that the water source was permanent, and even in drought when the river is not flowing, there is a deep sump along the length of the property, being replenished from a spring under the riverbed that maintains the sump at a near permanent level.

    4. I will not go into the detailed design specification here Peter, but to summarise that sufficient stars lined up for the final Off Grid Solution to include some cost effective earthworks in the ravine to create a dam sufficiently sized to support [1] a closed loop pumped pico-hydro secondary power source [16 hour duty cycle] combined with [2] a solar PV primary power source [10 hour duty cycle].

    5. Importantly this solution provides for a very cost efficient, high reliability autonomous Off Grid power generation system involving ground mounted Solar PV arrays, plus rotating electric motors operating as both pumps and generators, 24/7 x 365.

    6. There are several other knock-on ecological and environmental benefits from this design also, including a halt to further land scouring of the deep ravine due the dam construction and smart water control systems put in place.

    7. I will leave it at that for now Peter and I am not suggesting that any of the above applies to your property, but we now know that you have a rural property of 10 acres, and that is important news.

    8. Starting your Off Grid project with a site survey is still my considered recommendation.

    Lawrence Coomber

    • Peter Sie says

      Thank you for this Lawrence. A site survey is not going to come up with anything I have not already mentioned apart from using water off the roof. But I agree that a site survey is important.

      My dwelling is a stand-alone Dwelling where we are taking enough water off the roof to cover our water needs 100% (and storing in a 100,000 L tank). There will be no other contributing factors from the land, and we will therefore have to create a power plant which can cover our power needs.

      My biggest question mark is how big a margin should I allow for battery capacity? This website offers at least 15-16 on-grid models, but not a single off-grid model and that was why I hoisted my flag and asked for support sharing as I have no idea of sizing my battery needs in an off-grid model and I do believe that my question still meets the brief “Don’t Add Batteries to A 3-Phase Home Before Reading This”.

      So my questions still stand.

      Peter Sie.

  87. Brett Davis says

    Hi Ronald, Finn and other Learned Pundits,
    My 9kW Enphase System is nearly three years old and I have recently upgraded my house to 3-phase power. In the (hopefully) not too distant future, I plan to get an EV that I want to connect via a bi-directional charger. That way, it can also act as my household battery as per Finn’s ABC Radio interview back in February. The blog of which can be found here:
    In the immediate future I plan on getting the installer to come back to connect the two extra current transformers. But when they do this, I want to ensure my system is configured correctly to enable easy connection of the EV bi-directional charger at a future date. Would I be correct in saying that Configuration 13 is the way to go in my circumstances?
    Other considerations I should mention are that I run a 20kW 3-phase reverse cycle ducted A/C as well as a 19.5 kW heat pump for my pool. The heat pump is only ever turned on during peak power generating times, while the A/C probably runs more than half the days of the year.
    l would greatly appreciate anyone’s thoughts on the matter.

  88. ramesh iyer says

    Hi. Finn – was pointed to this article by one of the Solarquotes customer service staff. A great article. Well compiled and explained?. Thank you.

    Some of my doubts have been clarified after going through the article. A few still remain though. I have a three phase supply coming into the house. MY DNSP is Ausgrid and current retailer is AGL. The Solar system installed back in Dec 2017 comprises of 20 x LG Neon 2 – 335w panels, Single Phase SolarEdge SE 5000H inverter, MODBUS SE-WNC-3Y400-MB-K1 and three CTs. The system has been performing reasonably well till date. I am now considering a battery option for the two main goals are 1) protect against grid supply failures & still be able to generate solar power for self consumption and charging the battery and 2) use battery backup to power all the three phases (i.e. the entire power load) during non solar generation times which may not be more that 10KWh (guesstimate). Of course, I do understand that there will be situations where the battery storage may not be sufficient enough to service the load and therefore will draw power from the grid or face a blackout if there is a concurrent grid outage.

    What are my solution options to be able to achieve both the goals? If these have been addressed before, happy to be directed to the resources.

    • Ronald Brakels says


      There are battery systems that can provide backup power to 3 phases. One example is a Fronius Primo Gen 24 Plus inverter with a BYD HVM battery. Unfortunately, this will only be able to supply up to 6 kilowatts of power from the battery. If you instead require around 10 kilowatts, you can use an installer who designs battery systems and have them provide a system that will meet your requirements, but if you can get by with 5 or 6 kilowatts of backup power you are likely to save a considerable amount of money.

      I would normally recommend expanding your solar capacity to ensure you have enough solar energy to fully charge your battery on most days, but how important this is will depend on your household electricity consumption.

      • Thanks Ron for your reply. Much appreciated. Apologies for this delayed response. All things remaining the same with my current Solar Installation, I have put down a deposit for a Tesla PW2. No ETA as yet and could take a few months. As a part of the battery install, they are expected to to rejig the backup based on our priorities and practicality. Once installed and running for a few months, will review with the installer the efficacy of the solution and make changes as required. Will also check back with the experts in the forum like yourself.

  89. Morning Solar Pundits,

    I have recently moved into a new place, which has 3 phase power. I had a solar system intalled 3x Solaredge 6kw, 50x Jinko N-type panels. Roughyl a 21.8kw system.

    Looking at the usage im averaging 100kw use a day. 50kw self consumption and 50kw grid consumption. selling roughly 25kw back to the grid.

    My place has mutlple pool heat pumps, a massive AC system amongst 100’s other things. Average base rate usage when we are all asleep is 1kw (unsure why)…

    What battery configuration would work best for this scenario? I would essentually like to charge the batteries during the day and completely use them up after solar production stops. Also in a power failure scenario is there a way to get the batteries to charge from solar and for the house to use solar to stay on if there were a power outage?

  90. Lawrence Coomber says

    Your question was:

    I have a 3-phase connected property, wired for solar, but have been dragging my feet re installing solar for a number of reasons.

    Re your earlier comments, in summary, does this mean you can have separate installs for each phase? E.g. off grid, on grid mix

    Cheers Tony


    An On Grid System means it is connected to the GRID.

    A Single Phase Inverter therefore must be connected to 1 Phase of the Grid [Single Ph and Neutral – Consumer Mains Supply].

    A 3 Phase Inverter must be connected to the corresponding 3 Phases of the Grid [Ph A, B, C and Neutral – Consumer Mains Supply].

    You can have many On Grid Inverters in your premises connected to the Grid, up to the capacity permitted by the Supply Authority and in accordance with your approved system design applications.

    Off Grid Systems mean they are NOT connected to the Grid. They have nothing to do with the Consumer Mains Supply. Ever.

    Off Grid Systems can exist though, side by side on a premises with On Grid Systems for a variety of cost effective specific purpose applications; but they remain at all times COMPLETELY SEPERATE OF EACH OTHER IN EVERY WAY and do not share any electrical connectivity.

    As independent Power Sources though, On Grid and Off Grid Systems can through Smart Switching Controls, supply similar load circuits including Battery Storage: and this is the real strength of considering installing an Off Grid Stand Alone Solution along side an On Grid System because there is effectively no size limit for Off Grid Systems like there is for On Grid Systems. Caveat: for STC’s purposes the maximum PV/Wind/Hydro kW installed on any one property, cannot exceed a combined total of 100 kW to remain eligible for STC’s.

    It’s a complex subject for non specialists though. Talk to somebody experienced in this subject who can interpret your unique circumstances into a worlds best Power Generation Solution.

    Hope this helps a bit Tony.

    Lawrence Coomber

  91. James Winters says

    So I’m in a right old bind.

    I currently have 7.62kw Panels with a single phase 6kw Solaredge coupled to a LG Resu 10H. I am wanting to upgrade to 3 phase at the house as I’m getting a pool in and an EV. So I want to add more panels to the roof at the same time.

    The LG battery is under recall, and has been for some time and I note now I can ask for a refund, which I’m probably going to do.

    So what is the best way forward to get another 7.6kw on the roof and a 13kW/h battery when I convert to 3 phase?

  92. Dennis Monamy says

    Nearly all my customer are going OFF-Grid.

    Most are purchased one or two 5kW Hybrid inverters, and one is currently looking to purchase Three inverters, as they want to have an inverter for 3 separate buildings (3 Phase Power)

    All customers either purchase Two or Three 10.24kWh Meritsun or YiY LiFePO4 Battery’s connected in Parallel to One Solar Array & Charged by just one Inverter.

    So, what System Configuration would you suggest ?

  93. Finn Peacock is clearly a Microinverter lover!
    Why? … because they are the very best.

  94. Alan Pegler says

    Hi all at solarquotes, We are looking at putting batteries on our house. We currently have 32 x 330w seraphim panels with a 10 kw 3 phase Solis inverter (sunboost ). The panel array currently is 24 panels are on a East facing roof and 8 are on a North facing roof ( this is the best we could do with our roof configuration ). Have you or anyone had feedback on LifePO4 battery packages? What I am looking at is (3 ) 48v EVE 280ah 13.44KWH battery pack kit with 200A Deligreen smart BMS with 1A active balancer & 5A parallel module, (1 for each phase). I will get a cabinet made up to house these in next to power box. This was installed 5/2020 and we used to enjoy zero bill with a credit every quarter but since Endeavor energy had a price restructure 2022 this no longer happens due to an increase in feed in tarrif and a major decrease in export tarrif, needless to say I no longer export. I am not going to make electricity to virtually give to my provider so they can make a profit off our investment. ANYWAY, I am not an electronics whiz and do not understand about the different voltage kits so what else would I need to buy with this to step up 48v to 240v ? Should I need more solar panels to charge batteries up I have enough room on the west facing roof to put another 32 panels. Please, all and any feedback would be greatly appreciated and if what I have proposed seems feasible a contact of someone who could hook it all up for me once I install. Thankyou Alan.

    • I would suggest you stick with 10.24kWh Battery Modules, as they are approx. 100kg each. The YiY or Meritsun are two good batteries.

      Make sure you order with a Wall Hang Bracket, as it makes mounting easier.
      With the AU$ so low 30kWh will currently cost you approx. AU$16’750.

    • Ronald Brakels says

      Hi Alan.

      It’s great you have a 10.56 kilowatt solar system, as you can expect to regularly fully charge a typical home battery. I’m not familiar with the batteries, so I can’t say what they are like. LiFePO batteries are one of the most popular types of lithium battery to use for household energy storage, but quality and reliability can vary greatly so it pays to be careful.

      For a household with typical electricity consumption, your 10.56 kilowatt solar system should be large enough to meet all your needs except in periods of extremely bad weather, but if your electricity consumption is high you could benefit from installing extra solar capacity.

      I definitely recommend investigating different battery systems that are currently available to see what may suit you. For many households, 10 kilowatts of solar and 10 or so kilowatt-hours of battery storage is more than enough to become mostly independent of the grid. But going fully off-grid is a much larger step and much more expensive and so I don’t recommend it for currently grid connected homes.

      If you like, you can get up to three quotes from battery installers through SolarQuotes. Just go here…

      …and enter your postcode. Then select “Upgrades” and then “Add batteries to existing solar system”. After that, answer the questions that come up as best you can. An installer can look at your consumption, suggest what type of battery system may suit you, and answer questions specific to your situation.

      If you have any other questions, please don’t hesitate to ask.

      • I tried your quote system but it’s not what I was expecting. I wanted to know if our 38 panel 10 kws system on 3 phase would be able to support a battery on it to run if we had no electricity from the grid and also charge if we had no electricity from the grid to keep using it. So far no one has been able to do this and it’s frustrating to say the least … how do I find out this information. We unfortunately got sucked in when we bought it only to find out it’s not available in Australia at this time. Gots to show how unscrupulous some solar providers are. Thanks

  95. I was wondering the same before I installed my solar battery. If the grid is down, you cannot charge your battery. Apparently, there is some regulation about that…more knowledgeable people can chime in.
    As concern the rest of your question it will all depend how much electricity you consume. It is nothing to do with one phase or three. It will all depend on your inverter. If your inverter is 5 KW, you will not be able to use more than 3 KW from your battery at the time…check with the battery manufacturer. We consume a lot of energy at home and I changed my inverter to 10 KW and now we can use up to 8 KW discharge from the battery. However, if we do this we will deplete the battery in few hours…Hope this helps

    • Hi thanks for your reply . We have a 10KW system. And 38 panels . On 3 phase . We were duped into thinking we could add a battery at a later date which would give us ongoing electricity in a power failure and it would also charge while the electricity was off. But at present I’ve just changed providers and our bill is still not high but in these times we are starting to look at battery instillation and going off grid if prices increase too much , hence my original message . Thanks for your answer cheers Jo

      • A Battery Bank will Power a Hybrid Inverter to supply 240V Power, if the Inverter is able to be Set to First Draw Power from the Battery, then Solar & Grid become Secondary Power Options !

        Solar only (Grid-connected) Inverters, can be AC Cabled to an Off-Grid Hybrid System, like in above modeling.

        I recommend you Invest in a Hybrid Inverter that can Start a Generator when Batteries are Drained & there is No Solar &/or State Grid Blacks-out.

  96. Ian Stuart says

    Great article, helped explain a lot to me, thanks!

    I’m looking at installing a PW2 and PV array. My installer is recommending a 3-phase invertor (which I understand) but I’m concerned that this will mean that (a) the PW can only charge from 1/3 of the array and (b) I lose the ability to charge the PW at all if the grid is down (which I can cope with).

    Have I misunderstood and should I go singe phase invertor if not?


    • I don’t think you can charge the battery from the Solar if the Grid is down…at least I was told this before we installed our battery.
      I think the importance of the inverter is how much will allow the battery to discharge. With the PW, I think is 4 KW. The three phase is more helpful how to distribute the back-up power when the Grid is down. You can set how the battery is charged when you charge it. Our is 3 KW during the day..the rest is used or exported back to the Grid.

      • Darryl Winder says

        i think that might have been true once but it appears there are inverts that can provide power from the PVs in a blackout w/wo battery

        • Thank you for the info. I wasn’t aware about Delta. I have Fronius Gen 24. Since my system was made of LG panels and Fronius inverters and I had to make sure that everything was compatible with the battery. I think this info will be more suitable for new built solar systems.
          I have been using BYD battery already for 2 months and haven’t had any issues. Fronius Gen24 is awesome apart of the delay switch over of 30-40 sec at blackout, no any other issues. Much more quite and efficient that the Fronius Primo and Sumo. BYD Battery is not compatible with Delta and/ or Enphase inverters.

          • Got it, so the constraint is that you can’t charge the battery whilst in blackout (unless you have one of the newer invertors). But I’m not restricted from using all of my PV to charge the PW with a 3 phase invertor?


          • When the system is installed the installer will set how to charge the battery. My is set on 4 KW during the day. So when you produce the solar, first the house needs are covered, than the battery up to 4 KW. If you produce more, goes back to the grid…again the inverter plays very important role..hope you started to have more clear picture…took me awhile to understand how it works…

    • Ronald Brakels says

      Hi Ian.

      Here’s a helpful video on the complications of using a Powerwall 2 with a 3 phase Australian home:

  97. Thanks for the article!

    I have an issue with three phase system that I noticed after I started to monitor the system. (The inverter is SOLAX X3-Hybrid 15kW)

    I have set the work mode to “Self Use” and programmed to charge the battery during the night from grid and discharge during daytime to power the loads. The problem is that some of battery´s power is taken to the grid. I would like to use all of battery power for the loads (self-use).
    For example, at 4:45 yesterday the power taken from the battery was 1857W. The loads used 1097W of it and 724W was transferred to grid. I have already enabled the phase unbalanced in the advanced settings, but it doesn´t seem to make a differnece. Are there any other settings I have missed or what could be the solution?

  98. I currently have a maximum of 10kW coming from ebphase microinverters into a tesla power wall 2 providing whole house backup as a single phase installation. 3 phase is available at the meter box but only one phase is connected.

    The battery doesn’t quite cover us overnight. We have only had the system since November so have not gone through a winter with it. I am considering getting a 2nd powerwall but don’t think the 10kW inverted power will be sufficient to supply my needs and charge both batteries especially during winter. I am limited to 10kW inverted capacity on the single phase with ausrid in NSW.

    Using configuration 13 with 3 cts, would this allow me to increase my inverted capacity beyond the 10kW as I am allowed 10kW per phase, so 30kW? Doe this also mean I am able to backup my entire house including possibly adding 3 phase consumers down the track, charge the batteries during an outage, consume on all three pased from the battery?

    Ultimately I want to increase my solar and storage whilst not having to go off the grid.

  99. Probably you could but instead to spend money on another PW and inverter isn’t it wiser to add extra panels? You worry about the winter but is 10 KW will be sufficient to charge 26 KW PWs? Do you worry about return on investment? If you keep charging the PWs how much export will make to receive some money back for repayment? Just a thought…

    • I want to add more panels, but at the moment configured as single phase I am unable to add more than the 10kW that I have. I was/am looking to see if I can use the other two phases to add up to 30kW of panels. But if I go to the 3 phase, I don’t want to lose the whole house backup. Looking at my December data, I have only had 4 days where I sent less than 13.5kW to the gird, so it should be able to keep two powerwalls charged up each day, noting I wouldn’t deplete the entire capacity of both each night. I am happy with the investment if I can run entirely on self-generated energy and take whatever feed in I can get.

  100. Andrew McDonald says

    Sounds like an exciting proposition and I wish you all the best.
    I’ve been online for a month watching a friend’s 10kW of solar panels power his new 28.8kWh of batteries. He gets a lot of sun and little rain, so the batteries are fully charged by lunch on most days. There is also plenty of electricity for his family to use during the day or sell back to the grid, not that anyone is getting much for doing so. He usually buys just one or two kWh once a week, which he feels is great.
    The Tesla Powerwall 2 is regarded as the best, but they are a little pricy. Even in the more expensive places for grid electricity, do you think that you will breakeven over the length of the ten-year warranty? Great if you are purely environmentally conscious or have an unreliable grid connection, but the outlay for another Tesla is a concern.
    You may also like to have a look at the anticipated life of LiFePO batteries. If they are only expected to have 60% of their original capacity after ten years, you might be drawing a lot more from the grid in 2033 and at a much higher price than what you are saving in 2022.
    I’d also ask about the circuits to be backed up by the batteries. From what I’ve seen, you should be able to back up most of them, provided you do not exceed the 5kW Tesla output limit. Giving the oven and hot water tank circuits a miss, is probably a good idea, given their load and length of time of draw.
    Let us know how you get on.
    All the best.

    • My systems seems to be consistent with you friend’s. I have set the pwrwall to supply until it reaches 10% reserve capacity.

      For December (daily) [max], [min], [ave], [month total], {kWh}:
      Energy Used: 73.2, 11.9. 31.8, 984.6
      Solar generated: 79.9, 24.4, 59.6, 1846.2
      Used from pwrwall: 19.3, 5.3, 10.7
      Used from grid: 12, 0.1, 1.6, 50
      Sent to grid: 58.2, 0.1, 28.1, 871.2

      I think we are likely to break even, especially if energy prices keep increasing, as well as it will still have at least 70% capacity at the 10 year mark. With a second pwrwall, I think we would be able to get up to 10kW out, 5 from each at a time, but I may be incorrect. There definitely is times around dinner when I am not generating much solar energy that I exceed 5kW, like when multiple of the the oven, AC, electric wok, kettle, hot plate etcetera are running.

      Having the battery has given us the carefree ability to use more energy than we would have before, like leaving the aircon on indefinitely unless away for most of the day or longer it gives me confidence that everything will remain on in a power outage (unless we have already consumed the entire capacity) and keep charging if in the day.

      Noting this is all summer data, I think the best idea is to wait until I have a year of data and see if the new government starts rolling more incentives for residential batteries, or perhaps higher time of use feed in tariffs. Another idea might be to hold off on a second pwrwall until the current one is further through its life. Two full capacity pwrwalsl will definitely exceed our needs at the moment, a brand new one and one with 70% (or 50%) of its original capacity might make more sense.

  101. Andrew McDonald says

    Hey Paul,
    Like your thinking. Lots of options and a well thought-out timeline. Still worried about the breakeven.
    Thank you for your electricity usage numbers. May I put this proposal to you?
    Looking just at December where you drew 50kWh total from the grid, and using it as a typical month, which may not be accurate, then …
    Even if electricity prices rose to $2 per kWh, you are still paying only $100 a month for electricity, ignoring the daily supply charge. That’s just $1200 per year. Even after fourteen years, you still would not have covered the cost of a new Powerwall 2.
    Uninterrupted power whilst the rest of the street is in darkness due to blackout; yes. The comfort of knowing that you didn’t burn coal to illuminate your home; yes again. But breakeven, I’m not sure.
    Honestly, I suspect that LiFePo batteries are just a temporary technology interlude whilst the world gears up for hydrogen. It will be as ubiquitous as current petrol stations. Homes will have solar power that generates hydrogen which is stored and used in fuel cells for overnight power. Lavo are offering residential units in Australia now.
    Either that or the new Graphene/Sodium battery technology.
    Enough of my prophesising.
    Best wishes

    • Hi Andrew.

      I think you are correct, economically it is hard to justify a second battery at this stage, I will wait see what the future holds re: battery costs and new technology.

      I am not so sure about the current offerings from Lavo especially after looking at reviews from this site. I am impressed that the technology exists to store hydrogen and use it to generate electricity and even more impressed that there is a domestic offering. This may be something that improves over the next decade when I will start to need to look at adding to a degrading battery.

      Fully onboard the hydrogen train though, I think it will play a massve role in the future, at least for heavy industry and transport but hopefully domestically. Since getting the solar and battery installed I have realised the limitation of it with respect to an electric car. The battery in the vehicle will be much larger than the battery for the house which I mostly deplete for the home each night and when I am generating excess after the battery is charged, the majority of the time the car will not be at home. It would still be cheaper to charge it on off-peak rates and through solar on the weekends, but it is disappointing that I won’t be able to charge it entirely off my own solar.

      I look forward to where hydrogen goes over the next decade. Thank you for your replies.

  102. Patrick Weir says

    Finn Peacock’s configuration #5 is what I have at my place with 3 CT’s in the meter box (on the house) and 3 CT’s on the 3 Ph inverter outputs (in the garage, 40 metres away), but I cannot see how my single Powerwall 2 (in the garage) can help on the other 2 phases, because it is physically wired to only one of the phases.
    (The house meter box CT readings are relayed by Wi Fi (Neurio) to the Tesla Gateway box in the garage).

  103. I’ve had powerwall 2s on a 3 phase install since 2019. The sparky moved most loads to the ‘Powerwall phase’ and I’ve not had any real issues, other than

    – if the load on a non powerwall phase goes above 3.3kW while there’s little to no solar production ( that’s the amount the powerwall can offset by exporting on its phase – Energex QLD), then it will import the shortfall.

    – no blackout prevention on the other 2 phases, which for me is minimal anyway

    – Three phase appliances won’t work during blackout/backup.

    • Patrick Weir says

      I am subject to Ausgrid here, and I am not sure if my Powerwall 2 is offseting for usage on the other 2 phases.. Does the Powerwall 2 do that automatically, or do I have to start offseting by connecting (by Wi Fi) to my Gateway and making changes?
      The smart meter that Ausgrid gave me is the Atlas Mk.10D, which is not a net reading meter, so Ausgrid only get a reading of the sum (usage – solar generation).
      My Powerwall Companion (software) graphs tell me that I got 98% self powering on the phase connected to the Powerwall 2 for all of 2022.
      My Energy Australia electric bills tell me that I sent 2149 kWh of electricity back into the grid during 2022.
      The Energy Australia feed in tariff is 7.6 cents per kWh, and my (fixed) plan usage tariff will go up to 36.07 cents per kWh on 1st March 2023.
      I need to get my head around this stuff, so I can decide if the Powerwall 2 can feed into the grid (offsetting, if it is not already doing so) and replace usage tariff (at 36.07 cents per kWh), while still being able to charge up sufficiently.


      • Ronald Brakels says

        Hi Patrick

        When configured normally your Powerwall 2 will detect if your home is importing power from the grid on the phases it is not connected to and will then export an equal amount of power on the phase it is connected to — until the Powerwall 2 reaches its maximum continuous power output of 5 kilowatts. For example, if there is no solar generation and your home is consuming 1kW on each phase then the Powerwall 2 will provide 3kW of power. One kW will be consumed by the home while the other two will be exported. The electricity meter will consider the home’s net imports of electricity to be zero. If you want to test this you can turn off everything at night and then turn on devices connected to different phases and see that your electricity meter doesn’t consider your home to be consuming electricity until the load exceeds 5kW.

  104. Hi I recently got a quote for a battery solar system for my 3 phase home , the sales person said I would need 3 separate batteries of 3kw each being the best way to do it which of course is going to inflate the cost ,is this true i would need 3 batteries and is there a way to only use the one battery by way of certain modifications?

    • Finn Peacock says

      You can put a single-phase battery on one phase of a 3 phase home, no problem. Here’s an FAQ I wrote about doing it with a Powerwall, but the same concepts apply to any AC coupled battery.

      If you want a DC coupled solution – there are a number of 3 phase hybrid inverters now available which can run 3-phase from a single battery.

      I’ll ask Anthony to do a longer blog post on this.

  105. Hi there,
    Thanks for this. I think I finally understand how single phase batteries work in a 3-phase home! Based on what I have read, one advantage of single phase batteries like the Tesla PW2 is that you can charge it from your solar during grid failure. I was under the impression that you can’t do that with a 3-phase battery, however I have recently come across an installer who says you can. I wondered if anyone here has experience with this? Regardless of that, if you have a 3-phase home and price is no object, would you generally recommend a 3-phase battery over a single phase battery? Thank you

  106. I have an existing 6kW PV array connected to a Fronius Symo-5-3M, (3 phase 5kW) inverter. I export about 9MWh annually.
    Is it possible to retrofit a battery using a DC-DC controller to charge it connected directly to the panels and the input side of the inverter?
    If so then during the middle of the day when the inverter output is clipped at 5kW then the PV over-supply could be used to charge the battery (even better if I had a 6.6kW array as most now are)?
    If it is possible and available then this would be independent of single, 2 or 3 phase systems and get around most of the 16 convoluted solutions presented above.

  107. This Blog shows; Configuration #11 above:
    Shows 3 batteries, 3 inverters and Not sure why a single-phase solar inverter is shown as that inverter becomes obsolete and is NOT required !

    This Page does Not show the Solar Arrays fed into the Master of 3x Hybrid Inverters to Produce 3 Phase.

    With each Inverter having a Battery connected in Parallel or via a Bus-bar to share the load & Charging.

  108. Hi there,

    Thanks for the article, it did help me to understand the designs better.

    I have the below query and hope the forum clarifies it;

    My house is connected to 3 Phase supply.
    I have 2 solar systems, 1)3.3KW system with single phase inverter and 2) 13KW with 3 Phase inverter.

    I am planning to get Tesla Powerwall 2 and most likely will go with Configuration #5: 3CT’s with AC coupling.

    I was told by the salesman that powerwall cannot be charged by panels in case of grid shut down as 3Phase inverter will be turned off.

    My question is as I am having a single phase inverter also, whether it would be possible to charge the powerwall using the panels during the grid shutdown?


  109. I was wondering if anyone has had any experience with tesla power walls with solar across different phases.

    Currently have 10kW with micro inverters on a single phase with a telsa power wall. Limited to 10kW per phase by ausgrid. Recently had a pool and spa built with a heat pump which can heat the spa individually or the pool and spa at the same time, lots of power. The house has 3 phases to it, but only using a single phase at the moment for all household including heat pump consumption.

    Looking in the future to get more solar, another 10kW on a second phase which Currently has nothing on it, I could move the heat pump onto the 2nd phase if desired.

    Mu understanding from what I could see is that the Tesla gateway will essentially treat a second battery as a single battery with doubled capacity at least if it was on the same phase but maybe regardless.

    With 2 batteries and cts for each phase, if I had the 2 powerwalls on a single phase would the solar on a different phase charge the powerwalls before sending to the grid? I understand that the powerwall will use the cts to essentially balance what is being consumed with what is being generated but would solar on a second phase be able to charge batteries on the primary house phase. So say phase A and B are both generatinf 2kw each assume nil house draw, would the powerwalls charge at 4kw? Or would 2kw from phase A charge the batteries whilst the solar from phase B go to the grid?

    Alternatively if a pw was installed on phase A and B, would the stored energy from both A and B be able to provide power to phase A in the event of a blackout? Trying to work out if the gateway can do this or is the balancing of drawing and supplying through cts just mathematically offsetting consumption and genration across phases. Would the consumption on phase A be limited to the battery on the same phase in a blackout with a battery on phase B inaccessibleto consumption on Phase A?

  110. Hi. We are on 2-phase (yes, you read that correctly). We already have 14kW of solar spread (NNW facing @15 degrees) across both phases with separate Solax X1-5 inverters which are limited to 5kW output each. We are on a rural property with the need for ongoing power even when the grid goes off, to support water pumps in case of fire. The alternative would be installing thousands of dollars of generators or complex petrol water pumps. We are now ready to install batteries and are about to purchase an electric car. We could install as much as 15kW more solar on the WSW facing roof if needed. We also run a B&B on the same power. I’ve received one quote which was 2 tesla powerwalls connected separately to each phase without CT’s – so I’m doubting that’s the most efficient. I’m also conscious that the current inverters limit the charging capacity of the batteries in that setup. Your article is fantastic. But given my unique circumstance I’m challenged which setup option would work best for us. Any thoughts?

    • Anthony Bennett says

      Hi Nigel,

      It depends on your budget of course. Do you know is the rural supply on a split phase transformer at your place? Or is it two out of three going down the road? Either way you’ll likely need two single phase setups, only the metering might change.

      For reliability I would bin the Solax. They’ve lasted longer as a company than many of the other cheapies but I wouldn’t call them great.

      Tesla are a good machine and are well known for doing just what they say on the tin. However I would prefer a DC coupled hybrid machine, they’ll happily blackstart if you run the battery flat and offer greater utilisation of solar by charging the battery with DC while simultaneously running AC loads. You couldn’t go far wrong with a Fronius or Sungrow single phase 10kW hybrid.

      If you want the most capable machine, one that will take starting pumps in it’s stride then there’s no substitute for the best.

    • Lawrence Coomber says


      Consider adding an Off Grid System at your rural property. Excellent for specific circuits that suit day time duty cycle operations like pumps, irrigation, battery charging; water heating etc etc. The list is long

      What is not often discussed or well known by installers is that any premises in Australia [space permitting] is able to install an Off Grid System [system 2] up to 100 kW [minus the size of the On Grid System [system 1], and be paid STCs for that size Off Grid System.

      Example: existing On Grid System = 15 kW therefore Off Grid System 2 can be installed up to 100 – 15 = 85 kW. That earns a considerable STC’s rebate.

      This dual system scenario is quite common particularly in industrial applications for Single Circuit Loads that have an appropriate day time duty cycle; for example a metal guillotine; compressor; press; aerator motors for fish farms; water pumps for filling reservoirs on golf courses, mining operations. The list is long and flexible in the hands of an experienced Power Plant Solutions integrator.

      These principles are equally valid for domestic premises; rural premises etc, and of course can be integrated with any size storage stack if required.

      Lawrence Coomber

  111. Grant Dell says

    Morning Finn, I have just switched my home to 3 Phase. My old 5kw solar is working but my AC coupled battery doesn’t seem to charging. I did briefly when system turned on but emptied the battery quickly few hours later and didn’t charge after that, even when full sun and plenty of free solar?

    • Anthony Bennett says

      Hi Grant,

      Speak to your installer. Depending on brand & model some batteries have CT coils on the mains cables to measure energy flow, and if your average electrician has changed the service they may have omitted or cocked them up.

  112. Hi Finn,

    I am writing to inquire about the black start capabilities of the Fronius Primo GEN24 10.0 and the Fronius Symo GEN24 10.0 inverters, particularly in relation to a Tesla Powerwall 2 setup. My research indicates that both inverters possess black start capabilities. However, I am specifically interested in understanding how this functionality operates in a house with a 3-phase grid connection when paired with a 3-phase inverter like the Fronius Symo. Could you please provide detailed information on whether the Fronius Symo GEN24 10.0, when used with a Tesla Powerwall 2 in a 3-phase setup, supports black start capability?

    One of your diagram(#7) says that I should only choose single phase inverter to have blackstart capabilities but just wondering if this is now outdated.

    Thank you for your assistance,

    • Anthony Bennett says

      Hi Fred,

      We are in the process of writing an updated guide to 3 phase hybrid systems because a lot has happened in the last few years.

      The Gen24 being a DC coupled hybrid means that they have voltage available from the roof at sun up and it can be used to charge the battery directly without needing an AC coupled machine to boot up and form a steady AC waveform.

      Your Tesla powerwall isn’t really a proper grid forming machine and they’ve withdrawn support for using them in off grid applications. When you have a powerwall islanded from the mains supply, they use frequency shift to ramp down the AC coupled solar if the battery is full, which is quite effective.

      There are specific requirements for having a maximum of 5kW AC coupled solar capacity online when a Powerwall is operating without the grid.

      However if your Powerwall runs flat overnight it will not form a grid to black start the solar inverter.

      Tesla are also incapable of forming a 120° 3 phase synchronous grid. You can have a powerwall on each phase of a 3phase supply, and they’ll back up individual phases in an outage, but they won’t play nicely together to drive a 3phase load.

      I would want to clarify with Fronius themselves, because one of the unique quirks in the Gen24 is that they run at 53Hz when there is a grid outage. This is a specific design feature used to make sure that any downstream AC coupled solar is shut down. I have not tried putting an ac coupled battery downstream of a Gen24, it might work when the grid is up but wouldn’t cope with 53Hz during an outage.

  113. Hans Prychocki says

    Just had a FRANKLINWH Battery installed a couple of months ago. And the reasons i went with them was, Capacity, Looks, Got a really good deal on Battery and install, which was tied in with the fact that they had just come into the Australian market. I had been looking at them for some time. So i thought i had done my research. Not so; Found out when the grid went down just recently the WH means whole home backup does not mean whole home backup. Duh only parts of the home remain with power. Because it is a single phase Battery. My BADD and my home is 3 Phase. If your home is single phase the Battery is WH. And i have been told and i can stand corrected that the majority of homes in USA are single phase so Wh works. Lesson learnt Regards Hans

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