YPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

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: Many battery systems can do this. You just need to check that the one you buy works optimally with your three-phase supply.

Warning: The salesperson 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.

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: 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.

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.

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 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.

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.

Configuration #4: 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.

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

Configuration #7: 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.

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

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

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

Configuration #11: Three batteries, three battery inverters and an 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 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.

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

Configuration #14: 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.

Configuration #16: 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.

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:

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.

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of SolarQuotes.com.au. My last "real job" was working for the CSIRO in their renewable energy division.

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.

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.

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.

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?

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.

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.

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?

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 😉

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.

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.

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!

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

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: https://imeon-energy.com.au/three-phase-hybrid-solar-inverter-imeon-9-12/ (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.

“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.

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.

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.

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!

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.

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!

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.

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.

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.

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.

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

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.

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?

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?

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.

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.

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!

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).

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?

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.

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)

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

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.

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.

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.

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)?

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.

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?

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?

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.

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.

You will need to purchase a StorEdge and have it connected to your 3 phase inverter. Then it will be able to support a high voltage LG Chem RESU battery.

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.

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.

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

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.

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: https://support.solarquotes.com.au/hc/en-us/articles/115001986773-Is-my-grid-connect-solar-system-100-compatible-with-a-Tesla-Powerwall-2-battery-

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.

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:

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.

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.

“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.

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.

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.

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.

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).

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.

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.

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.

Tony: 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.

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? Thanks, Can

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? Thanks, Cam

#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 https://cleantechnica.com/2018/10/12/tesla-powerwall-price-features-new-coming/

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.

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.

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.

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?


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. Cheers, Gavin.

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 ?

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

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.

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.

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)

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.

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.)

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

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.

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?

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.

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.

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.

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.

“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.”

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.

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.

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.

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.

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.

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

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?

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?

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.

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.

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

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.

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.

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?

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.

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

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? Thanks, Cam

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.

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?)

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.

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!

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.

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.

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.

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.

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 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.

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?

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.

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.

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.

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

Download the first chapter of The Good Solar Guide, authored by SolarQuotes founder Finn Peacock, FREE!

You’ll also start receiving the SolarQuotes weekly newsletter, keeping you up to date on all the latest developments on Australia’s solar scene.

4pole Rccb

Circuit Breaker, Solid State Relay, AC Contactor, Surge Protector - Kampa,https://www.kampaelectric.com/