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.

Let me start with some basic facts relating to three phase solar in WA.

The largest inverter capacity for residential, allowed now is 15kW
You are more likely to be approved for what you want up to 15kW than before when the limit was 30kW.
If your inverter(s) is larger than 5kW then your inverter must be export limited to 1.5kW
Also, if your inverter(s) is larger than 5kW your inverter will NOT be turned off by Synergy
You MUST install a device, usually an inverter 'smart or consumption meter' to enable export limiting.

"What is this I've heard about Synergy turning inverters off?"
Many people are confused by Synergy's new Emergency Solar Management rules.
The rules are reasonably straight forward.

If you install a new solar installation, or make ANY changes to an existing one, including adding a battery after 14/03/2022, then...

If your inverter is 5kW or below, Synergy can remotely and instantly, turn your inverter off if they need to.
They won't be selecting a street here or there, they will turn them all off.
They won't be ramping down production, at least for now, it's fully off.
So you might have a perfect solar day and yet be buying power from the grid.
'Shut down' is achieved by connecting to your inverter via the WIFI link you have with your inverter manufacturer's reporting platform.
No, they can't access anything else in your house. I am assured of that.

If you don't have WIFI, or simply pretend not to, then they will, at your expense, install a 4G dual meter in your switchboard and get us to
connect it to the solar circuit in your switchboard, and they will turn the inverter off that way instead.

If you have inverter(s) greater than 5kW then they won't turn you off.
They do, however require you to purchase an inverter 'smart meter' which can cost $600 or more so that your system is export limited to 1.5kW.
Why they didn't require zero export is beyond me, they don't want your solar, but 1.5kW it is.
You don't get paid for any exports either, but there again, you never did anyway if you were over 5kW.

Why are they wanting to turn inverters off?
Too much solar, too few people to sell it to.
Nowhere to store it.
It costs them money to buy your solar that they don't want.
Having nowhere to send the solar power to, causes issues with their equipment.
Voltages rise to levels where their equipment and yours, can be damaged.

How often will they turn inverters off?
They say it will be 'very rare' and not for extended periods of time.
It will happen when conditions are perfect for solar production but not hot or cold enough for people to use their aircon.
They call these times 'low load events' and they are most likely to happen in October/November and March/April.

At the moment they are not talking about compensation, or giving those affected free power during the event.
Early days. We shall all just have to wait and see what unfolds.

What three phase solar inverters are there in Australia?
The most popular three phase inverters are Fronius, Huawei, Sungrow, Goodwe, SolarEdge, SMA, Growatt and Solis.
With the new 15kW limit, there are solutions with either one larger inverter or multiple smaller ones.
Having multiple inverters for larger systems offers some benefits for placing panels every which way.

This past 12 months we have seen a very significant increase in the number of people installing new solar with batteries.
The majority go down the hybrid inverter path, which for three phase, I agree with.
DC coupling a battery directly to the inverter with 3 phase is in several ways, a superior solution than AC coupling a battery
(e.g. Tesla Powerwall 2).

Fronius Symo GEN24 Plus 8kW and 10kW hybrid inverters with BYD batteries have been particularly popular.
Huawei only have 5kW and 6kW hybrids but we've done plenty of installs with 2 or 3 of these linked as one, with the Huawei battery.

Often having multiple inverters is a panel design bonus, as for each extra inverter we have 2 more MPPTs to work with.

Sungrow have a 10kW hybrid and their own battery, and we've been impressed with the results from these installs as well.
SolarEdge have a range of three phase hybrids, up to 10kW too, but as yet, their own battery doesn't work with them.
We have also done a few Goodwe three phase hybrids with LG and BYD batteries too.
Every one of these inverter/battery solutions have their advantages and disadvantages but nothing is perfect.

So plenty of choice. When we know what features you want and what your roof is like we can make some suggestions.

You can oversize any inverter (add more panels) by 133.33% without a battery.
So a 10kW inverter can have 13.3kW of panels or a 5kW 6.66kW of panels.
It gets more interesting when a battery is connected.

Huawei and SolarEdge three phase inverters, with a battery allow 200% oversizing.
So their 10kW inverters can have 20kW of panel power or 5kW can have 10kW of panel power.
Fronius, Sungrow, and Goodwe 3 phase hybrids are more conservative with 150% oversizing.

The extra panels are subsidised by the Government STC discount scheme.

I want a battery, and I want backup power when the grid goes out.
Very popular requirement, but never all that simple to get the perfect solution.
It is highly unlikely that you will be able to provide backup power for your entire house.
Forget aircon, pool pumps, and think lighting and power outlets only.
If you live in an area where there is a risk of fires, then a supply to the pump would be good.

Sungrow and Goodwe have all the circuitry for backup built-in with their hybrid inverters, the rest require an extra box of breakers, contactors, relays.

One of the big advantages that three phase hybrids have is that they can continue to charge the battery when the grid is out.
By contrast, if you buy a regular three phase solar inverter, say a Fronius Symo, and then install a separate Tesla Powerwall battery which has its own inverter inside,
then when the grid goes down the Tesla can power the house until the battery is empty, but can't keep the Fronius Symo alive
to keep the solar power working. On single phase, no problem at all but three phase, no.

Can I connect single phase inverters to three phase?
You can connect 1 x 3kW inverter, or a 3kW and a 2kW but you can't connect a 5kW single phase inverter unless it has a battery connected.
If there is a battery connected, then it must be export limited to 3kW.
Now and again we come across a house where this sort of configuration works better than a three phase inverter, but its rare.
For those puzzled about how solar can work where only one or two of the three phases has an inverter connected, the answer lies in the
way the electricity meter works. Simply put, the meter does a calculation every ten minutes of all the power imported from the grid on all phases against all the power it has received from the house on all phases.
It then deducts one from the other and you either owe Synergy money, or they possibly owe you, or it's break-even.

Let me allow Western Power to explain it their way....

The Western Power (WA) Rules

"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)."


(08) 6102 2527


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This review was written by Andrew MacKeith, Solar4Ever service manager since 2011.
Solar4Ever is located in Morley (Perth), WA 6062