Tools · Solar

Solar payback estimator.

Drop in your assumptions. The calculator shows every step it takes to get to the payback figure. Change the numbers and watch the working update.

Inputs

Your roof and tariff

System sizeTotal kWp installed

kWp

Install costAll-in, after VAT

OrientationCompass direction

Shading factor0 = none, 0.2 = light, 0.4 = heavy

Import rateYour tariff's day rate

Export rateSEG or smart export rate

Self-consumptionShare of generation used directly

Working

The maths, shown

Annual generation3,491 kWh

— used at home1,222 kWh

— exported to grid2,269 kWh

Bill savings (year one)£336

Export income (year one)£340

Year-one total return£677

The headline figure

Payback: 10.0 years

Assuming 0.5% panel degradation per year and stable tariffs in real terms. The breakeven point is sensitive to the import rate above all else.

A note on assumptions: annual generation is derived from a UK baseline of 1040 kWh/kWp, adjusted for orientation and shading. Real systems vary by ±10 percent against this baseline. We deliberately do not factor in inverter replacement at year 12-15, which would push payback out by roughly a year.