Estimate annual solar generation, bill savings, export income and simple payback from your own system assumptions.
This is a simplified estimate. Actual output, tariffs, degradation, maintenance, finance costs and future electricity prices can change the outcome.
How to use the Solar Panel Calculator UK
Enter the proposed system size and an annual yield supplied by a competent installer or solar assessment. Add the share of generation you expect to use in the property, your electricity unit rate, export tariff and installed cost. The calculator does not insert default assumptions, so the result reflects only the figures you enter.
How the solar estimate is calculated
| Result | Calculation |
|---|---|
| Annual generation | System size × annual yield |
| Electricity used at home | Generation × self-use percentage |
| Bill saving | Self-used electricity × import rate |
| Export income | Exported electricity × export rate |
| Simple payback | Installed cost ÷ annual benefit |
Why annual yield matters
A panel system’s rated capacity is not the same as the electricity it will produce in a year. Location, roof direction, pitch, shading, inverter performance and system losses all affect annual generation. Use a property-specific assessment rather than treating the example placeholder as a recommendation.
Self-use and exported electricity
Electricity used while the panels are generating can replace electricity bought from your supplier. Surplus generation may be exported. Under the UK government’s Smart Export Guarantee guidance, eligible small-scale generators can be paid for electricity exported to the grid, but tariff terms and rates vary by supplier.
Understanding simple payback
Simple payback divides the entered installation cost by the first-year estimated benefit. It is useful for a quick comparison, but it is not a full investment forecast because it does not model panel degradation, inverter replacement, maintenance, tariff changes, inflation, financing or the time value of money.
Related calculators
Estimate building demand with the Heat Loss Calculator. Check thermal transmittance with the U-Value Calculator. Compare wider efficiency measures with the Home Energy Savings Calculator. Browse every tool on the United Kingdom Calculator homepage.
Frequently asked questions
What does kWp mean?
kWp means kilowatt peak, the rated maximum output of a solar PV system under standard test conditions.
Is the example annual yield suitable for every UK home?
No. The placeholder is only an input example. Use a property-specific figure that reflects location, orientation, pitch, shading and system losses.
What is the self-use percentage?
It is the share of generated electricity used in the property rather than exported to the grid.
Does the calculator include a battery?
Not separately. If a battery increases expected self-use, enter the resulting self-use percentage supplied by your assessment.
Is simple payback a guaranteed return?
No. It is a basic estimate using the entered first-year values and does not guarantee future performance, prices or income.