Interactive estimate
Estimate solar payback
Change the inputs to see how generation, self-consumption and export income affect the break-even point.
Visible assumptions
Regional generation is estimated as kWh per kW installed. Self-consumed solar is valued at the import rate. Exported solar is valued at the export tariff. The calculator does not model panel degradation, tariff changes, finance costs, inverter replacement or roof-specific shading.
How the payback estimate works
The calculator estimates annual generation from system size and UK region, then splits that generation between electricity used at home and exported electricity. Home-used solar is valued at your import unit rate. Exported solar is valued at your export tariff.
Payback is the estimated installed cost divided by annual benefit. This deliberately keeps the maths visible. It does not model panel degradation, inverter replacement, tariff changes or finance costs.
Assumptions to check before using the result
Self-consumption is the assumption most people overestimate. A home that is empty in the day may use less solar directly unless it has a battery, timed appliances or flexible loads.
Generation also varies by roof direction, pitch, shading and location. A south-facing unshaded roof in southern England is not the same as a shaded east-west roof in northern Scotland.
Common questions
What is a good solar payback period?
Many homeowners look for a payback period that fits inside the warranty life of the system and their likely time in the property. Shorter is better, but comfort with the assumptions matters just as much.