System size comparison
How to choose your system size
Three factors matter most:
1. Your quarterly electricity bill
Under $300: a 5 kW system covers most usage. $300–$600: 6.6 kW is the standard. $500–$800: step up to 8 kW. Above $700: 10 kW or larger.
2. Your daytime usage pattern
Households that use most of their electricity during the day (pool pumps, ducted air-con, electric hot water, work-from-home) get more value out of a larger system. Households that use most of their power in the evening should size more conservatively or add a battery.
3. Your future loads
Planning an EV in the next 2 years? Add 2–3 kW to whatever you'd otherwise install. EVs typically double a home's electricity demand. Planning a heat-pump hot water replacement? Add 1 kW.
Common questions
What size solar system do most Australian households install?
6.6 kW is the most-installed residential size in Australia — it pairs with a 5 kW inverter (the legacy standard) and hits the sweet spot of federal rebate, real-world generation, and easy DNSP approval. Around 65% of new residential installs are 6.6 kW.
How do I know what size I need?
Quarterly bill is the cleanest signal. Under $300/quarter: 5 kW. $300–$600: 6.6 kW. $500–$800: 8 kW. Above $700: 10–13.2 kW. Adjust up if you have a pool, electric hot water, ducted air-con, or an EV.
Does a bigger system always pay back faster?
No. Payback is fastest at 6.6 kW for most households — the federal STC rebate scales linearly with size, but exported electricity earns less than self-consumed electricity, so bigger systems with low self-consumption can have longer paybacks. Add a battery to make a bigger system pay back faster.