Solar and 3 phase power



Approximately 20% of Perth homes have a 3 phase supply. There are a few ways to check whether you have three phase or not. You could see if you have three black
boxes under or above your electricity meter (see picture above), you could look at what is labelled as 'Main Switch' and see if it has three breakers, or you could ring Synergy and ask them.

We have a different set of rules in WA compared to those on the East Coast of Australia.


On the East Coast, they can connect a 5kW single phase inverter to a three phase supply.

The magic of net metering makes that work (financially) as explained further down this page.


In WA we can only connect up to a 3kW single phase inverter to three phase, which is why you see so many older 3 phase installations over here with two inverters.
e.g. A 3kW plus a 2kW, or 2 x 2.5kW.

The reason why these homes didn't just get a three phase inverter, was that back then, there was very little choice, and what was available was very expensive.


The frustration of WA rules.

There are plenty of people who can fit much larger systems that a 5kW inverter and 6.6kW of panels, but if they do, in WA, then they lose all of their feed in tariff...the 7 cents per kWh payment for surplus power. So if you install a 10kW inverter and 13kW of panels and make 60kWh of solar power per day, but only use 10kWh of it 7am to 5pm (solar hours), the surplus flows out to Synergy who take it, "Thanks very much". No payment for you. You can't even 'export limit' the inverter to 5kW and get paid for just that.


So, because of that, we tend to make mostly 5kW three phase inverter sales.


Up until very recently, the bulk of those sales would be the Fronius Symo inverter. We also installed a few of their hybrid (battery) version but the extra $940 price put most people off it.


Then Huawei arrived with their 5kW 3 phase hybrid (battery) inverter and pitched their price $300 below the regular non-hybrid Fronius. They also went one step further than the usual 5+5 warranty (5 years parts and labour + another 5 years parts only) and gave a full 10 year parts and labour warranty.


It's not like Fronius haven't faced three phase competition before Huawei arrived.


SMA Tripower for one, made in Germany, and a few dollars cheaper than Fronius

Goodwe, Sungrow, Growatt all had excellent 3 phase inverters, often $600 or so less.


But none of these were hybrid, battery, inverters, and that's what people are increasingly asking for.


One of the other big attractions of a hybrid inverter is oversizing.
Even though you might be restricted to a 5kW inverter because of the feed in tariff rules, the rules change when you connect a battery to the inverter. You start with the usual 33.3% oversize (e.g. 6.6kW of panels running from a 5kW inverter). Then when you are ready to plug in the battery you add further panels (up to 8kW is the realistic limit) and you can claim the Government discount (STCs) on those extra panels. The hybrid inverter can then channel that extra panel power directly into charging up the battery. It's still a 5kW limited inverter. It can't convert more than 5kW of panel power into AC, so if it were a normal inverter with 8kW of panel power coming at it, it would be forced to 'clip' off the extra 3kW and waste it as heat, but the hybrid just stores the extra in the battery.


You can see the costs for all these three phase inverters on our Prices page.


Goodwe introduced new 5kW and 10kW three phase models mid 2019 and very good they are too. Like Fronius hybrid they support LG and BYD high voltage batteries.


Larger 3 phase inverters
If you don't care about losing the FIT or are a business where you don't get the FIT anyway, then there are plenty of inverters for you to choose from, although, for most, they go straight to Fronius Symo whose extensive range goes up to 20kW, and then 27kW with a single MPPT and very slightly cheaper 'Eco model'.

Huawei won Intersolar 2019 'Best Inverter' with their new M0 range. The 5kW and 6kW models are hybrids, the 8kW, 12, 15, 17 and 20kW models are not, but they all support Huawei optimisers and therefore panel level monitoring if required.


SMA Tripower goes up to 25kW in 5kW increments, Sungrow 5kW to 20kW also in 5kW increments



Connecting single phase inverters to 3 phase.

For those of you wondering how a single phase solar inverter only connected to one of the phases is going to power your home, the answer is it isn't. It will only provide power to loads on the phase it's connected to. However, that's not a problem because our electricity meters are all 'net meters' so that means it doesn't matter as far as your financial return goes.

Explained by Western Power below, with our translation below that.



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)."

Let's say that the single phase solar inverter was connected to Phase A and that you had absolutely zero loads on that phase. All of your loads were connected to Phases B and C

The solar inverter would produce it's power but as there were no loads requiring it, the power would flow to the electricity meter that would record let's say 0.8kWh received and exported from you during the 10 minute cycle.

In that same 10 minute cycle your loads on Phases B and C used up 1kWh.
So 1kWh was imported from the grid.


The meter add up all the imports (1kWh) and the exports (0.8kWh) across Phases A, B and C and determines that in this particular 10 minute block of time, you need to pay them for the difference, 0.2kWh