How many solar panels do I need?
Tell us your postcode, roof orientation, and how much roof you have. We size the system to your actual location's solar irradiance and your real annual electricity use.
Your property
Recommended system
Updates as you change the inputs.
- System size
- — kWp
- Panels needed
- —
- Annual generation
- — kWh
- Annual savings (self-consumption)
- £—
- SEG export income (estimate)
- £—
- Estimated install cost
- £—
- Payback period
- — years
How the sizing works
Solar PV sizing is a balance between three things: how much roof you have, how much electricity you use, and what your roof faces. Most UK homes are constrained by roof area before they hit their annual electricity demand — a typical pitched roof has 25–40 m² of unshaded slope, enough for 4 to 6 kWp of panels.
UK solar irradiance
The UK averages around 950 kWh of generation per kWp installed per year, optimally oriented. That figure varies by region — Cornwall and south Devon get closer to 1,050; the Highlands and north-east Scotland sit around 800. Roof orientation modifies the output: south-facing gets the full irradiance, east or west falls to ~85%, north drops to ~60% and rarely justifies the install cost.
Self-consumption vs export
Solar electricity used in your home displaces grid electricity you'd otherwise pay for (typically 27p/kWh in 2026). Solar electricity exported to the grid earns you the Smart Export Guarantee (SEG) tariff, which varies by supplier but averages around 8p/kWh in 2026. Without a battery, most UK homes self-consume roughly 35–50% of their solar generation. Adding a battery pushes that to 65–80% and shortens payback.
What this calculator doesn't do
The output here is indicative, not a survey. A proper installer's quote accounts for shading from trees and neighbouring buildings, roof pitch, structural load capacity, inverter location, and DNO export limits in your area. Use this as a starting point before requesting MCS-certified installer quotes.
Frequently asked questions
How many solar panels do I need for a UK home?
A typical UK home (annual electricity use 2,700–3,500 kWh) needs a 3–4 kWp system, which is 8–10 panels at 400W each. A larger four-bedroom home running 4,500–6,000 kWh annually usually sizes around 5–6 kWp (12–15 panels).
Does orientation matter for solar panels in the UK?
Yes. South-facing roofs generate roughly 950 kWh per kWp per year. East / west panels generate about 85% of that. North drops to 60% and usually isn't worth the install. SE / SW orientations sit between south and east/west at 95% of optimum.
How long is the payback on a UK solar system?
At 2026 prices a 4 kWp installed solar system costs around £6,000–£8,000. Combined self-consumption savings and SEG export income deliver payback in 8–12 years. Adding a battery shortens that significantly.