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Calculator · Rooftop solar

What size solar system do you need?

Find a simple starting point for panel capacity and panel count from your postcode and electricity use.

Two details to start

Use the average daily electricity use on your bill. If you do not have it, try a household estimate.

We use it to find your Clean Energy Regulator solar zone.

2. How much electricity do you use?

Look for “average daily use” on a recent electricity bill. A full year of bills is better because seasons differ.

Your result

A starting size, without a long questionnaire.

Enter your postcode and daily electricity use to see the panel capacity that could generate about that much energy over a year.

What this number means

We convert the Clean Energy Regulator’s annual zone rating to average daily output per kW, then divide your daily use by it. The result is the panel capacity whose annual generation roughly matches annual use. We round the daily output to two decimals and the panel size up to two decimals before rounding up to whole 440 W panels.

This does not mean your panels will cover every hour. Solar output changes by season and weather, and a home can export energy at midday while buying it back at night. Roof direction, shade, inverter limits and your electricity plan can change a suitable installed size.

Before you request quotes

Check several seasons of bills, any plans for an EV or electric appliances, and the sunny roof space available. Ask installers to show their expected monthly output and the assumptions behind it. Network export limits and inverter rules also need checking for your address.

If your home already has solar, your bill omits energy used directly from your panels. Use your inverter’s consumption data for total daily use when available.

Already considering a battery? Size it here →