The quick answer
A typical UK household uses 2,900 kWh of electricity per year (Ofgem, 2024). To offset half of that, you need roughly 10–12 panels (4kW system). Each modern panel generates about 350–400W and produces around 300–350 kWh per year in Leeds.
Calculate your needs in 3 steps
- Check your annual electricity usage. Look at your energy bills or smart meter app. The average is 2,900 kWh but a large family or EV owner might use 5,000–8,000 kWh.
- Decide your target coverage. 50% is realistic without a battery. With a battery, you can push to 70–80%.
- Divide by panel output. In Leeds, each 400W panel produces about 320 kWh/year. So: (target kWh) ÷ 320 = number of panels needed.
| Annual usage | Target coverage | Panels needed | System size |
|---|---|---|---|
| 2,000 kWh | 50% | 4 | 1.6 kW |
| 2,900 kWh | 50% | 5 | 2 kW |
| 2,900 kWh | 70% | 7 | 2.8 kW |
| 4,500 kWh | 50% | 7 | 2.8 kW |
| 4,500 kWh | 80% | 12 | 4.8 kW |
| 7,000 kWh (EV) | 50% | 11 | 4.4 kW |
Roof space matters
Each panel is roughly 1.7m × 1.0m, so you need 1.7m² per panel. A 4kW system (12 panels) requires about 20m² of unshaded roof space. Most semi-detached houses in Leeds have 20–30m² of usable south-facing roof — enough for 12–18 panels.
East/west-facing roofs work too, just with 15–20% less generation. Check our roof orientation guide for specifics.
Does it have to be exact?
No. Slightly oversizing your system is usually smart — surplus electricity earns money through the Smart Export Guarantee (4–15p/kWh). The cost per panel drops as system size increases, so adding 2 extra panels might only cost £800 more but generate an extra £100–£150/year.
Get free quotes from Leeds installers — they'll survey your roof and recommend the right system size for your home.