Solar panel calculator UK

Explore how system size, site yield, self-consumption, electricity price and export value can change the economics of home solar.

WHAT THIS CALCULATOR TELLS YOU

A useful solar estimate needs more than panel count. Generation, how much electricity you use while it is being produced, the price of imported electricity and the value of exported electricity all affect the result.

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

Generation

Array size (kWp) × the yield assumption you select.

Self-use

Generation × your self-consumption percentage, capped by annual electricity demand.

Annual value

Avoided imported electricity cost + entered value of exported electricity.

HOW TO INTERPRET IT

Use the result as a scenario.

A 4 kWp array does not have one universal annual output or saving. Change the yield and self-use assumptions and you can see why two otherwise similar homes can have different results.

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 this a roof survey?

No. Orientation, pitch, shading, usable roof area, equipment and local conditions require a property-specific assessment.

Why does self-consumption matter?

Electricity used directly in the property can replace imported electricity. Electricity not used at the time may be exported or stored.

Should I use the highest yield option?

No. Use the options to explore sensitivity, not to choose the most attractive result. A formal proposal should justify its site-specific generation forecast.