Solar panel payback period UK: formula and example

Your solar payback period is the time it takes for bill savings and export income to cover the upfront cost of the system. It is a useful sanity check, but it is only as reliable as your assumptions. This page explains the payback result; use the main calculator to create your own estimate.

The simple payback formula

Payback years = upfront system cost ÷ annual benefit. Annual benefit = self-used solar value + export income.

Worked example using current defaults

Input or result	Value
System cost	£7,000
Annual bill saving	£329
Annual export income	£351
Annual benefit	£680
Simple payback	10.3 years

What counts as annual benefit?

Self-used solar: kWh used in your home multiplied by your electricity unit rate.
Exported solar: kWh sent to the grid multiplied by your export tariff.

What is a good payback period?

Energy Saving Trust’s published examples show solar payback varying by location and household routine, with current examples around 9 to 12 years when export payments are included. That doesn't mean your quote will match those figures. A high-cost system, poor roof or weak self-consumption can be much slower; a strong roof and a suitable tariff can be better.

Why batteries can confuse the headline

A battery can reduce later grid imports, but it also has losses, may displace export income and adds its own installed cost. Start with the solar-only result, then judge the battery separately from its net annual battery benefit and battery-only simple payback.

How to make your payback estimate more realistic

Use your actual import unit rate and accessible export tariff.
Use installer generation estimates, then test a 10% to 20% lower case.
Model solar-only first, then compare a battery using its usable capacity and incremental installed battery cost.
Compare total net value over 10 and 20 years, not only payback years.

Next: use the solar savings calculator · calculate annual savings first · what affects payback · separate battery payback