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Solar panels

How many solar panels do you need?

Most homes are limited by roof space before anything else. Within that, size the system around the electricity you use, and the electricity you expect to use if you add an electric car or a heat pump.

Updated 3 October 2026 · energy.org.uk editorial team

The short answer

Energy Saving Trust describes a typical 3.5 kWp system: it takes up around 20 m² of roof and could generate over 3,000 kWh a year, about the same as a typical home uses. Modern panels are usually around 400 to 450 watts each, so 3.5 kWp is roughly eight or nine panels.

To estimate for your own roof and postcode, use the solar panel calculator. It uses long-term sunshine data for your location.

Matching your yearly use is not self-sufficiency

Even a system that generates as much as you use in a year will not cover your use day by day:

  • Most generation happens from late spring to early autumn, and little in winter.
  • Panels generate in the middle of the day, when many homes use least.
  • Electricity you don't use is exported, usually at a lower rate than you pay to import.

So a home with panels still buys electricity, especially in winter and at night. A battery can move some daytime generation into the evening; see solar panels with or without a battery.

Check

What to check first

  • Your yearly electricity use, from your bill or annual statement.
  • Future loads. An electric car or heat pump raises your use, mostly in winter for a heat pump. See charging an EV from solar panels.
  • Usable roof area, after allowing for chimneys, windows, vents and gaps at the edges.
  • Direction and shade, which change how much each panel produces. See is your roof suitable for solar?.

Do

Practical next steps

  1. Enter your postcode and roof in the solar panel calculator.
  2. Ask installers to quote for the largest system your roof suits, and a smaller one, and compare the payback of each.
  3. Check how much of the generation you would use yourself, not just the yearly total.
  4. Compare quotes on price per kWp in the solar quote checker.

Take care

Important limitations

  • Panel sizes and wattages vary; the number of panels matters less than the total kWp.
  • Larger systems may need extra approval from your network operator before connection, which your installer arranges.
  • Generation varies from year to year with the weather.

Related tools and guides

Sources

Official sources checked 3 October 2026.