Best solution for a 3-phase home

Hi All

I am looking for the best solution for a 3-phase home.

My first idea was 2 single phase inverters on a phase each (see attached pic)

But I have been advised that a 3-Phase inverter might be a better solution.

My first choice would be Victron equipment (hence the 2 single phase inverters) with Pylontech batteries, but I am open to other brands. For the 3-Phase solution, SolarEdge seemed to be a good pick, but apparently the battery integration is much more complex??


It seems that you drink a lot of coffee if that machine shares half the inverter with the kitchen :smiley: ! I like your priorities.

Could you give us more detail (if you have it) on how much power you need/use on each phase/db. What is your total consumtion, as well as peaks?
Some equipment like the welding and borehole might need the 3 phase, but it could be that all the rest could run on just one phase and then you only need one inverter for it’s back up. That would save you much and be less complicated, but it would depend on your usage and needs.

Would it also be useful to understand how billing works? Whether he gets billed the net across all phases and whether he gets billed individually per phase? I.e. is it possible to feed back on one phase to cancel out the load on another phase for billing purposes.

Ja thanks coffee IS important…

The 3-Phase thing is maybe a mental-block on my side. If you give it up with our municipality it is difficult and hugely expensive (R100k +) to get back. But to be honest I probably don’t need it. If I keep it I need to try and do phase-balancing to get my COC or so I’ve been told.

Usage wise it will be a biggish household (still renovating) and my medium to long term plan is to be off grid, but Eskom is still there if you really need it. We had a Studer XTH 6000-48 in the previous house and we’ve only ever tripped it once when the dishwasher, washing machine and tumble dryer were running during load shedding (weekend kids in hostel). But our geysers and stoves were not on the inverter. So, I assume one 6000 is not enough even with a solar/heatpump geyser setup.

The billing is prepaid and is the sum of the 3 phases. Feeding back to Eskom sounds like a complicated idea!?

Bear with me! Electricity novice!


Which municipality are you in?

I’m not sure about the phase balancing to get your COC. Someone else will need to comment on that.

If you can put everything on one inverter it will be a very large cost saving. And so much simpler which would meen less things that can go wrong. That would be my suggestion.
If you want to go blue, then the 5kVA Multiplus II is a good option and it has all the certifications to be grid-tied and get a COC. (4kW continuous power with a 9kW peak)

It sounds like you are making things more complicated than they need to be, from what I can see you have no 3-phase devices.

Just convert your house to single phase and get one single phase Sunsynk 8kw (they have a 12kw as well now) inverter. I did it and it works like a charm. I even have a 3-phase pump running of a VSD so 3-phase devices can be accommodated if necessary.

Is really easy for an electrician to do and takes about 5 minutes, does not involve rewiring your DB-Board. They just need to bridge the phases on the supply so you are only running of one phase.

As long as you are not going to be pulling more than 60A (13.8kw) of the phase you will be fine.

My hamster goes to the pub when it comes to 3 phase, however from my understanding you have options.

A 3 phase AC PV inverter like a Fronius on the house and then you put a Victron inverter on only one of the phases for your night time / battery consumption. You split your phases and put all essentials on the Victron phase. The non essentials, borehole, pool pump, oven, aircons etc. doesn’t have to be on the Victron phase.

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Would he be able to reduce non-essential energy consumption if he wires it this way? If the non-essentials are all on a separate phase, surely he can’t reduce his grid usage on those?

Like I said my hamster goes to the pub, come in @JacoDeJongh
But if I understand correctly the essentials and non essentials will still be able to run off the AC PV by day.
The essentials will run off the Victron / battery by night.
And if you want to use non essentials at night they will run off Escom

Yes. When using a Fronius and AC-coupling the PV, the Victron system will limit the PV-inverter so that the total over the three phases is zero, even if the Multi is only on a single phase. You will have to install a 3-phase energy meter though.


Makes sense! I missed the Fronius part (a little under the weather and in bed).

And in getting a single inverter, might even be able to go for one of the bigger Multis.

@plonkster And during loadshedding he will have to rely solely on batteries? Could it be possible to put in a change over to move the Fronius to the critical output of the Multi? And can such a changeover be automated with the relay on a GX?

If it is a 3-phase Fronius and a single-Phase Multi, then no. If three single-phase Froniuses, then yes, you could put one on the output (but the cost of that would be prohibitive, compared to a single 3-phase unit).

The Multi will also feed energy into L1 to compensate for loads on L2 and L3, given that the billing arrangement bills on the total.

Side note: Don’t worry if the phase where you want the Multi isn’t L1. Simply rotate the phases (physically, or relabel for the sake of the installation) so that the Multi ends up on L1. As long as the rotation is correct, the system doesn’t care if it is L1-L2-L3, L2-L3-L1, or L3-L1-L2.

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Maybe then it would be easier to changeover the solar array to an MPPT, sized to the essential loads. However, it does seem like quite an expensive solution for the odd event of the grid going down for longer than the batteries can deal.

You should also bear in mind that most of the 3-phase inverters are in essence three smaller inverters linked together.

So, 12kw3-phase = ±3 x 4kw inverters

Fronius 12.5kw for example, max current is 19.9A = 4.5kw

So, if you go over 4.5kw on one of your phases you will overload the inverter.
This makes the balancing of your phases much more important.

Would be better in my opinion to convert to a single phase. You can run your 3-phase borehole pump of a VSD without any issues and you could then also run it off the solar with a soft start.

Would speak to them to find out if they have a suitable one for running your 3-phase welding machine of one as well

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There is a 16kw Sunsynk single phase inverter that was recently released, the thing is a monster.


Thanks for the input and interesting conversation.

I think the answer is clear – I will change to single phase and maybe use the “3-phase saving” to get a bigger system.

I am still keen on Victron. A Quattro 10000 with a nice bank of Pylontech? Or for a bit more a 15000 – a bit like hunting Impala with a .375H&H – effective :wink:

Who are the best Victron suppliers/installers in the Western Cape? I am in Hermanus.


If you are in the W/Cape, make sure the inverter you get, has an NRS certification. Trust me on this one.

Quattro does not have NRS last time I checked. You need to look at the Multiplus II.

I think @JacoDeJongh is more in CT that up north these days. Send him a private message.

Yes. But in this scenario they are grid-coupled, so if you go over 4kW on any phase, the rest simply comes from the grid, and because the billing arrangement is that the total power over all the phases is accumulated into a total, the balancing isn’t as big an issue.

In an off-grid situation with a Hybrid inverter (eg Voltronic used to have 10 kW infini that was 3.3kW per phase, and Fronius has a hybrid too), you are absolutely correct though. Just because you have 10kW doesn’t mean it’s available on every and any phase :slight_smile:

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