This guide answers how many solar panels you need for a UK home, using typical electricity use by house size, modern panel wattages and real roof space. It also explains why the same system size can mean different panel counts from different installers.
Quick answer: Divide the system size you need by the panel wattage. A 4 kWp system needs about 10 panels of 400 W or 9 panels of 450 W. For a typical 3-bedroom home using around 2,700 to 3,500 kWh a year, that usually means 8 to 10 modern panels.
How do you work out the number of panels?
- Decide on a system size in kWp, based on your yearly use. Our guide to what size solar system you need covers this.
- Divide by the wattage of the panels you are quoted, converted to kW.
- Round up, then check the panels fit on your roof.
How many panels for your house size?
Typical figures using 430 W panels and a yield of about 950 kWh per kWp. Usage varies widely, so use your own bills where possible.
| Home | Typical yearly use | System size | 430 W panels | Roof area |
|---|---|---|---|---|
| 1-bed flat or small house | 1,800 kWh | 2.0 kWp | 5 | about 10 m² |
| 2 to 3-bed home | 2,700 kWh | 2.8 to 3.5 kWp | 7 to 8 | about 15 m² |
| 3 to 4-bed home | 3,500 kWh | 3.7 to 4.3 kWp | 9 to 10 | about 20 m² |
| 4-bed home with an EV | 6,000 kWh | 5 to 6.5 kWp | 12 to 15 | about 25 to 30 m² |
Why do panel counts differ between quotes?
Panel wattages vary from about 350 W to over 500 W for domestic models. A higher wattage panel is usually physically larger, so the roof area needed per kWp stays similar. Installers also design around obstructions and the strings their inverter needs.
How much roof space does each panel need?
A typical 430 W panel is about 1.7 m by 1.1 m, roughly 1.9 to 2 m², plus spacing and edge clearance. Fire safety and wind loading guidance usually means leaving a margin around the edges of the roof.
What if my roof is small?
- Use high-efficiency panels to get more kWp in the space.
- Use both east and west roofs; output is lower per panel but spread over the day.
- Consider a garage roof, outbuilding or carport.
- A smaller system can still be worthwhile if most of its output is used in the home.
Frequently Asked Questions
How many solar panels does a 3-bedroom house need?
Usually 8 to 10 modern panels, giving about 3.5 to 4.3 kWp.
How many solar panels to run a house completely?
Matching yearly use is possible, but you will still import in winter and at night unless you also have a battery.
How many solar panels for 4 kW?
About 9 to 10 panels of 400 to 450 W.
Do more panels mean more savings?
Up to a point; savings depend on how much of the output you use at home.
Checked November 2026 by the Solaxyra Editorial Team. Sources: Energy Saving Trust: Solar panels, PVGIS (European Commission).