Nearly 30% told us that their solar panels provided between a quarter and a half of the total electricity they needed over a year. There's a huge seasonal variation in how much of your power solar panels can provide. Read our buying advice for solar panels to see how much of your power solar panels could generate in summer.
As we saw above, the average UK home uses around 3,731 kWh per year. So a 5 kW system, or possibly a 4 kW system, would probably do the trick. A 3.5 kW system usually needs about 12 panels 2, and a 4 kW system might need 14 or 15. You’ll need to measure your (south-facing!) roof to work out whether you can fit 14-15 panels up there.
Most home panels can each produce between 250 and 400 Watts per hour. According to the Renewable Energy Hub, domestic solar panel systems usually range in size from around to 1 kW to 5 kW. Allowing for some cloudier days, and some lost power, a 5 kW system can generally produce around 4,500 kWh per year.
A panel is usually around 2m², but your installer will need to leave room either side of each panel, and around the system as a whole. They’ll typically leave 40cm of space on all sides, and at least 3cm between the panels, to match the standards created by bodies like Microgeneration Certification Scheme (MCS) and Flexi-Orb.
To calculate how many solar panels you need, the only piece of information you need to find is your annual electricity usage, which your energy supplier will usually share with you each year. If you have an online account or solar app from your supplier, you may also be able to find your annual consumption that way.
Household solar panel systems are usually up to 4kWp in size. That stands for kilowatt 'peak' output – ie at its most efficient, the system will produce that many kilowatts per hour (kWh). A typical home might need 2,700kWh of electricity over a year – of course, not all these are needed during daylight hours.