Maximum Residential Solar PV System Size in WA

If you’re looking at investing in a solar power system, you may be wondering what the maximum sized system you’re able to invest in is.

Unfortunately, the answer is not a simple number. The maximum sized solar inverter you’re able to install will depend on three things, what phase you are; if you want to receive STCs; and if you want to be eligible for DEBS, the Distributed Energy Buyback Scheme.

Single or Three Phase?

• Single Phase
  If your home is located in WA and takes single-phase electricity, the maximum solar inverter size you can install is 5kW. This has been decided by Western Power, the state’s network operator.
  
  
• Three Phase
  In WA, inverters installed in homes with three-phase electricity are decided upon a case-by-case basis by Western Power, however, it’s roughly estimated to be 5kW per phase, meaning a maximum inverter 15kW in size could technically be installed.

The maximum size you’re allowed to install will differ from state to state. For more information on what is applicable for your state, please contact your local network operator.

STCs explained

The Small-scale Renewable Energy Scheme, under the Federal Government’s Renewable Energy Target, has been designed to create a financial incentive for those wanting to install small-scale renewable energy systems such as solar energy systems.

It achieves this through small-scale technology certificates, commonly known as STCs. The number of STCs any given renewable energy system generates depends on its location in Australia, the year it was installed, and the amount of solar power it is expected to produce up until January 2031, when it is being phased out.

To be eligible for STCs, your panel capacity must not exceed the size of your inverter by more than 33%. For example, if you install a 5kW inverter, you must not install over 6.65kW worth of panels. This is known as oversizing a system and is quite common.

Why should I oversize my solar power system?

High-quality solar inverters are designed to be able to handle oversizing, as long as the voltage limits on the inverter are not exceeded.

In fact, The Clean Energy Council Solar PV Design Guidelines recommend that you oversize your array by up to 33%, due to the fact that the maximum power output of a solar panel is measured under ideal test conditions, which do not often occur in real life. Therefore, it’s extremely rare that your solar panels will produce at their maximum STC rated output.

Downsizing your inverter slightly and spending more on additional panels may increase your solar power system’s output and provide a better financial outcome than simply matching the inverter and solar panels sizes.

Eligibility for DEBS

While 5kW is often referred to as the maximum inverter size for residential systems in WA, it’s not strictly 100% accurate for three phase homes.

Assuming Western Power gives you approval, you can install a solar inverter above 5kW in size. However, in doing so you’ll lose the eligibility to receive feed-in tariffs through Synergy’s Distributed Energy Buyback Scheme (DEBS).

This means you won’t receive any money for the solar power you export to the grid. Many homeowners are understandably unwilling to do this, however if you have an extremely high energy usage/bill, it may be worth exceeding the 5kW limit.

While you won’t be receiving a feed-in tariff, if your electricity consumption is high enough that you need an inverter larger than 5kW, you probably wouldn’t have been sending much electricity back to the grid with a smaller solar power system anyway.

With this in mind, it makes more financial sense to invest in a bigger solar energy system and offset more of the electricity you would have purchased from the grid for 26 cents per unit. After all, this is where the real savings of solar come from.

Is bigger always better?

While there are benefits to keeping your inverter below 5kW, the best sized solar energy system is one that exactly suits your lifestyle and requirements.

Having installed over 18,000 systems around WA, Infinite Energy are the experts in designing solar power systems to suit every home and family.

For a no-obligation quote, click here or give us a call on 1300 074 669