Free tool
Solar Panel ROI Calculator UK
Tell our solar panel ROI calculator how much roof space you have and how much electricity you use. It shows how many panels fit, what they'll produce, your projected monthly savings, the installation cost with or without safe battery storage, and how many years it takes to pay for itself.
A typical 3-bed semi has about 15–25 m² of usable south, east or west-facing roof.
The UK average home uses about 2,700 kWh a year – check your bill for yours.
Estimated monthly saving
£75
Up to 78% off your electricity bill · £900 a year
- System size
- 10 panels · 4.4 kWp
- Yearly generation
- 3,960 kWh
- Installation cost
- £11,500
- Payback
- 12.8 years
- Export income (SEG)
- £189/yr
- 25-year net saving
- £10,991
Estimates only. Your survey confirms the real figures for your roof.
How the solar panel ROI calculator works
- 1. Roof space to panels. Each modern 440W panel needs about 2 m² including spacing, so we divide your usable roof space by 2.
- 2. Panels to power. In the UK, each kWp of panels generates around 900 kWh a year (more in the south, a little less in Scotland).
- 3. Power to savings. Without a battery, a home typically uses about 45% of its solar power directly. With a battery that rises to around 80%. Each kWh you use saves 26.32p (Ofgem price cap, Oct–Dec 2026); the rest earns about 15p through the Smart Export Guarantee.
- 4. Cost and payback. We estimate installation at the best rates available, add battery storage if selected, then divide by your yearly saving to get the payback period.
Roof space vs solar performance
More roof space means more panels and more output. Here's what typical UK roof sizes can hold:
| Roof space | System | Suits |
|---|---|---|
| 10 m² | 5 panels · 2.2 kWp | Small roofs, flats with own roof |
| 20 m² | 10 panels · 4.4 kWp | Typical 3-bed semi-detached |
| 30 m² | 15 panels · 6.6 kWp | Larger detached homes |
| 40 m²+ | 20 panels · 8.8 kWp+ | Big homes, EVs & heat pumps |
Can solar cut my electricity bill by up to 80%?
Yes, for many homes. With enough roof space and a battery to store daytime solar energy for the evening, a household can cover up to around 80% of its electricity bill. Winter output is lower and you'll still pay the daily standing charge, so our solar panel ROI calculator caps bill savings at 80%.
Average UK household saving
For an average home using 2,700 kWh a year with 20 m² of roof (10 panels, 4.4 kWp) and a 9.5 kWh battery, the calculator projects about £75 a month (around £900 a year) in bill savings and export income, cutting the electricity bill by about 78%. Without a battery it's about £66 a month, with a lower installation cost.
Why add safe battery storage?
Modern lithium iron phosphate (LFP) batteries are stable and long-lasting. Our highly qualified team installs them to current UK safety standards so you can use your own solar power after dark.
All figures are estimates using typical UK assumptions. Your real savings depend on roof direction, shading, location, tariff and how you use energy. A free survey gives you exact numbers.