What Size Solar System Do I Need in Perth?

Choosing the right solar system size is one of the most important decisions in a solar installation. Too small and you're leaving savings on the table; too large and you're exporting cheap power you'll never recover the cost of. Here's how to get it right for Perth.

How Much Power Does Perth Generate per kW?

Perth is one of the sunniest cities in the world. A north-facing 1kW solar system in Perth generates approximately 4.2–4.5 kWh per day on average across the year (higher in summer, lower in winter). So a 6.6kW system generates roughly 28–30 kWh per day on average.

Matching System Size to Your Usage

Under 15 kWh/day (small household, 1–2 people): 3–5kW system
15–25 kWh/day (average 3–4 person home): 6.6kW system
25–40 kWh/day (large home, pool, EV): 10–13.3kW system
40+ kWh/day (large home with EV charging): 13.3kW+ system

Why 6.6kW Is So Popular in Perth

The 6.6kW panel array paired with a 5kW inverter is Perth's most popular combination. A 5kW inverter is the maximum single-phase export limit allowed by Western Power, and a 6.6kW panel array (oversized by 32%) generates more power during shoulder hours and cloudy days without exceeding inverter limits. It's also the sweet spot for the STC rebate and typical 3–4 bedroom home usage.

Roof Orientation

North-facing roofs are ideal. East-facing generates more morning power (good for early risers), west-facing generates more afternoon power (better for afternoon/evening self-consumption). Many Perth homes use a mix of north and west panels to spread generation across the day.