by
I love three-phase solar inverters.
If your home has a three-phase supply and you do not want or need micro-inverters then my recommendation is to use a three-phase solar inverter over a single-phase model.
A three-phase solar inverter takes DC electricity from solar panels, chops it up and sends it out as AC electricity shared across a three-phase supply.
They cost about $300 more than the equivalent single-phase solar inverter, but look the same:
Most homes in Australia have a single-phase electricity supply. This means that they have one live wire coming in from the grid.
A three-phase home has 3 live wires coming in from the grid.
This means three-phase homes can pull more power from the grid. Handy for particularly big loads such as a:
And of course a three-phase supply means you can send much more solar energy back into the grid compared to single-phase (three to six times as much depending on your local DNSP rules).
Carefully (don’t touch anything!) 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 homes will have 3 like this:
If you have three-phase supply you can have either:
Any of these choices are valid. It will not affect how you are billed for exports or how much solar energy is self consumed.
But, I still recommend a three-phase solar inverter.
Spreading the inverter capacity across the three wires coming into your home means that you don’t have to push the solar energy as hard to get it out to the grid. You’ll be increasing the local grid voltage less than a single-phase install and you’ll have less throttling or tripping off due to over-voltage issues. That means more solar power production with our high-voltage plagued Australian grid.
Voltage rise related solar issues are one of the biggest problems we see with installed solar power systems. I go in to detail on the causes and solutions for voltage rise issues here.
So to reiterate for the blog post skimmers:
If you have a three-phase supply I recommend getting a three-phase solar inverter. Why? Because it drastically reduces the chance of having voltage rise issues.
But not everyone agrees with me on this.
There is one downside to using a three-phase inverter other than the extra cost (expect to pay $300 to $500 more compared to a single-phase inverter). Three-phase solar inverters do make it much more expensive to have ‘Apocalypse Proof Battery Backup™’.
My definition of regular battery backup is this: when the grid goes down your battery system powers some specially selected ‘essential circuits’. If the battery gets drained during the blackout, your home will black out too. In this configuration, the solar panels cannot charge your battery without the grid.
My definition of Apocalypse Proof Battery Backup : when the grid goes down your battery system powers some specially selected ‘essential circuits’. But if the sun is shining the solar panels help power your home and recharge the battery too. If you are careful with your consumption, you can carry on indefinitely charging the batteries with the sun by day and using the battery at night.
If you have a three-phase home with a single-phase solar inverter (or microinverters) then, with the right battery – such as a Powerwall 2 – Apocalypse Proof Backup is easy and can be done out of the box:
When the grid goes down in this configuration the battery system isolates the house from the grid (islands) and keeps 230V on the ‘black’ phase so the solar inverter does not shut down. The solar panels continue to send power to the house and battery. The solar inverter is throttled using frequency shifting if there is ever more solar power than the house and battery can handle.
But if you add a battery to a system with a three-phase solar inverter it is more complicated. If the grid goes down you need to keep 230V on all three-phases to stop the solar inverter shutting down. A battery with a single-phase battery inverter (such as a Powerwall 2) cannot do this. You will be able to have ‘regular’ backup – but once the batteries are drained you’ll have no power until the grid comes back.
The solution to this is expensive. You either need a three-phase battery inverter – and if you know of one please let me know in the comments – I’ve never seen one for sale. It would look like this:
Or you have 3 batteries and battery inverters – one on each phase. But again – I don’t know of any battery systems that can play nice with a separate three-phase solar inverter. The Powerwall 2 cannot work in this configuration. Yet.
Or of course you could swap your three-phase solar inverter out for a three-phase hybrid inverter and DC Couple your battery:
But all these options are very expensive. So if you are choosing between a three-phase solar inverter and a single-phase solar inverter/microinverters the question you have to ask your self is:
In my humble opinion it is better to have a system that operates well 99.9% of the time (when the grid is available) over one that operates really well 0.1% of the time (when the grid is down).
But perhaps your grid electricity goes down much more than that and getting through long outages is your priority. In that case you may want to install a single-phase solar inverter on your 3-phase supply. Just make sure that your installer checks your local grid voltage and voltage rise before you get solar installed. And hope that your local grid voltage stays low in the future.
You could also install a three-phase hybrid inverter instead of a three-phase solar inverter. But bear in mind that any future battery must be compatible with that inverter – often that is only 2 or 3 battery models and they may be obsolete by the time you decide to buy them.
So choose wisely three-phase dweller. And do the right thing based on your local grid voltage, your local grid reliability and above-all your zombie tolerance.
×Sign up for our weekly newsletter!
Your email
For more information AC Coupled Inverter, solar hybrid inverter, please get in touch with us!