Solar payback calculator UK

Explore simple payback and longer-term undiscounted benefit using your own system cost, bill saving, export income and maintenance assumptions.

WHAT THIS CALCULATOR TELLS YOU

Simple payback is the installed cost divided by net annual benefit. It is useful for comparison, but it is not the same as a full investment appraisal and should not hide the assumptions behind the number.

Method reviewed: September 2026Assumptions are visibleIllustration, not a quotation

Outputs are simplified illustrations using the values you enter. They are not a prediction or guarantee of generation, savings, battery performance, charging cost or investment return.

HOW THE CALCULATION WORKS

Transparent methodology

Net annual benefit

Entered bill saving + export income − maintenance allowance.

Simple payback

Installed cost ÷ first-year net annual benefit.

Longer view

The tool compounds your entered annual benefit change, but deliberately does not pretend this is a discounted cash-flow model.

HOW TO INTERPRET IT

Use the result as a scenario.

If a proposal quotes a payback period, ask for the assumed generation, self-consumption, import tariff, export tariff and system cost. Small changes to those assumptions can materially alter the headline number.

For a real project, replace planning assumptions with site-specific design data, current tariffs, actual equipment specifications and a formal quotation.

CALCULATOR QUESTIONS

What the tool can — and cannot — tell you

Is shorter payback always better?

Not by itself. Equipment quality, warranties, system design, roof works, finance and how assumptions were calculated also matter.

Does this include panel degradation?

No. This simple explorer deliberately avoids pretending to be a full lifetime financial model.

Can future electricity prices be predicted?

Not reliably. Use scenarios rather than treating one assumed future tariff as guaranteed.