Three phase and solar


There are a few ways to check whether you have three phase or not.

Open your switchboard and look for three black fuses.(see picture above).
Check your 'Main Switch' and see if it has three breakers.
Single phase would be just one switch.
You could ring Synergy and ask them.

You are allowed to connect up to 10kW of solar inverter per phase, so 30kW in total.
Then you can connect up to 40kW of solar panels (108 x 370W)

In WA, until the recent drop of the feed in tariff to 3 cents, most people kept to the 5kW inverter limit. That limit, imposed by Synergy, says that if you exceed 5kW of inverter, then you get zero feed in tariff.

Now it's only 3 cents FiT, we are seeing many people consider larger systems.
They understand it is now a 'use it or lose it' situation, and that is why 'solar + battery' inverters are popular.

They aren't buying too many batteries yet, just preparing for the fast approaching day when we get forced onto 'Time of Use' (TOU) charging, and 3pm to 9pm power costs 60 cents or more.

Can I connect a single phase inverter to 3 phase supply?
In WA you must have the phases evenly balanced if you connect single phase inverters.

You could have a 3kW inverter on each phase, or even a 5kW. That's balanced.
You could have a 3kW and a 2kW, or 2 x 2.5kW. Close enough.
But, nothing larger than a 3kW inverter if that is ALL you are connecting.

The rules on the East Coast of Australia are different to ours.
10kW single phase inverters on 3 phase is fine for many electricity distributors.
Somtimes they insist on 'export limiting' the surplus to 5kW maximum.
In WA, we aren't allowed to export limit.

If I have a single phase inverter won't I lose money?
It's a perfectly logical question.
The inverter is on phase 1 for example, but many loads are on phases 2 and 3.
That's rather the point of three phase after all. Balanced loads, greater supply.

The electricity meter is the answer to most people's question of 'How?'
It varies a little across Australia but the principle is the same as it is in WA, as follows.

Firstly, the solar power would supply what it can to household loads on phase 1.
Any surplus would then flow to the electricity meter that would record that surplus as 'export'.
The power supplied to the loads on the other two phases would be recorded as 'import'.

But here is the 'light-bulb moment'.

Every ten minutes the meter adds up all the exports and imports, takes one from the other to reach a negative or postive 'net' amount across all the phases, therefore determining for that 10 minutes whether you owe them money or the other way around.

That's how a single phase inverter can work, without losing you money when it is only connected to one out of three phases, or for that mattter, if you had two single phase inverters on two phases. It simply doesn't matter.

The electricty meter, called a 'Net Meter' because it works out the 'net result every ten minutes' is why.

The Western Power description of this is explained in the highlighted red text at the bottom of the page.

What three phase solar inverters are there in Australia?
All the inverter manufacturers have both single and three phase inverters.
Some are better quality than others.
Some can connect a battery, others can't.

I want backup power from a battery during a grid outage
You could buy a regular 3 phase inverter and panels and then add on a Tesla Powerwall 2 later.

The only drawback with that is that the Powerwall can't keep your 3 phase inverter 'alive' during a grid outage,
meaning that once your battery is empty, it can't be recharged by the solar panels.
You would, in that case, have been better off with 2 or 3 single phase inverters which the Powerwall can keep alive.

Another option would be to buy a three phase 'hybrid' inverter and connect a battery to that.
Hybrids run both the panels and the battery, but again, there's a bit of an issue with backup during a grid outage.
Some hybrids provide backup split across three phases, others send it down a single phase.

So, for example, Sungrow have a 5kW and a 10kW three phase hybrid where the backup is split over three phases
So if it's a 5kW Sungrow you get 1.66kW per phase of backup or 3.33kW if it's a 10kW inverter.
Huawei 3 phase hybrids deliver 3.3kW backup but all on a single phase.
Fronius have a 3 phase 6kW, 8kW and 10kW hybrid with what they call 'Full back-up' but really means the same as Sungrow, split across 3 phases.
You also have to be aware with Fronius that you also need to buy a $1,500 backup box or breakers, contactors, relays etc whereas all of that is fully built into the Sungrow (and Goodwe)
Fronius also have a 'PV Point' that provides backup to an RCD protected outlet directly from the solar panels, no battery required.
Usually this outlet is wired up next to the inverter and it only works if the sun is shining, but it's a good thing none the less.

For a 10kW inverter, Sungrow would be better..3.3kW on each phase is obviously better than 3.3kW on a single phase.

But for a 5kW inverter solution...which is better?

That's not easy to answer because it entirely depends on what you are trying to keep alive during an outage.
Perhaps the priority is a single phase water pump for fighting bush fires and it draws 2kW.
Then the Huawei solution would be best because its got 3.3kW available, but the Sungrow has only 1.66kW.
If its a three phase load you are trying to keep going, then Sungrow would be better.
Sungrow would also be better if it's a lot of small loads across phases, because you have got 5kW available instead of 3.3kW

Which is the best 5-10kW hybrid three phase inverter and battery?
I wrote the previous piece first because the answer to this question very much depends on how much you care about backup.
If you have stable power and really couldn't care about backup then the answers become much simpler.
Huawei have an excellent 5kW (and 6kW) 3 phase inverter (M1 model) and a superb battery.
8kW, 10kW and 12kW models coming in 2022, we think, now that the Australian voltage standard has changed.
It's ultra reliable, stylish, fully integrated and great reporting. Just a superb battery and inverter combo. Backup box is an optional extra $1,000 item.

Fronius have a 6kW, 8kW and 10kW 3 phase inverter hybrid (Symo GEN24+) that works with BYD batteries (and soon LG).
Being Fronius it is expensive and I don't like that they aren't working with their own battery, but it's still a very classy inverter and will be no doubt, as reliable as the existing Symo non hybrid range.
They also have a 5kW model with no backup, PV point only as described above.


Sungrow have a 5kW and 10kW three phase inverter and their own battery, and excellent fully built-in back-up, as long as splitting acorss three phases works for you.

SolarEdge & Goodwe also have good hybrid inverters, but I think Sungrow, Huawei and Fronius would be at the top of most shortlists.



The Western Power (WA) Rules

This is how Western Power officially describes how their meter works...

"The 3 phase meter measures the combined consumption and

generation across all three phases continuously - it does not distinguish

between phases and then takes the net after a set period (of 10 minutes).

If there is excess generation on one phase, and a load on another phase,

then the excess generation will supply that load. If there is still more power

required, then the customer will receive electricity from the network and it

will be recorded in the meter as purchased/imported electricity. But if

there is still excess generation after supplying all of the household load,

it will be sent out onto the network and recorded as sent out (or exported

onto the network), which is where the customer receives REBS and/or FiT

(or neither if they aren't eligible)."