Single Phase Inverters with Three Phase systems

Will a one-phase inverter work on a three-phase house?

This is a question we get asked very frequently, and it’s a good one, it shows you are paying close attention to your home’s power, and are intent on making sure you get the very best in solar. So, let’s break this down.

What is three-phase? How do I know if I have it?

Three-phase power is when your home has three-phase lines connected between it and the grid. It is most commonly used in large homes that have ducted air conditioning systems or other systems that require a large lump sum of power, such as a bore pump. If you already know your home has three-phase ducted aircon, you can be certain you have three-phase power too. But there are a number of other ways to check if you have three-phase power, two of which we outline below.

Check your meter

While it’s possible to have a three-phase meter on a two-phase system, there is an easy way to ratify this. On your meter's display, check for the following: L1, L2, L3. If you have all three, that verifies that you are indeed on a three-phase connection.

Count your isolation links

Introduced in 2011, isolation links or Iso-links are added to a system so that you can disconnect power to the meter safely. If you have 3 isolation links, you have three-phase power.

So, will a single-phase inverter work?

The short answer is yes, it will. Your inverter will only push power into one of your home’s three phases, but from your point of view, this will not make a difference; you will receive the same benefits from the inverter as if you had a three-phase inverter.

What about my feed-in tariff? Will I still see a return? Won't I be paying for power on the other phases?

This is a common question when installing single-phase inverters in three-phase homes. Let's look at an example scenario. If your system is exporting 4 kW on one phase, but buying 1 kW on each of the other phases, will you be paying for those 2 kW of incoming power (the price of which is greater than the return you see from exporting the 4kW)?

As illustrated in the diagram below, this is not the case. Polyphase metering means both your imports and exports are being monitored and summed across all three-phases, not assessed individually. In this scenario, although you exported 4 kW and imported 2 kW, you net total would amount to 2 kW export, giving you the full benefits of solar production across all three phases.

 

Single/Three Phase