How Many Solar Panels Do I Need?

Start with your energy use

The best starting point is your annual electricity consumption in kWh — it is on your energy bill. A good installer sizes the system around that, your roof space and how much of your generation you would realistically use.

Roof space and orientation

Each panel needs roughly 1.7–2 square metres. Available unshaded space, roof direction and pitch then determine how many panels will actually fit and how much they will generate.

Bigger isn’t always better

Oversizing a system can mean exporting a lot of electricity at low rates rather than offsetting expensive imported power. Unless you are adding a battery or have high daytime demand (an EV, heat pump or home working), a sensibly sized system often makes more financial sense.

Get it sized properly

Any installer quoting a system without asking about your energy use should be treated with caution. Compare several quotes and see who takes the time to size it correctly.

This article is general information. Costs and savings vary by property, energy use and tariff.