Each calculator publishes its data, its assumptions and its arithmetic. They run entirely in your browser: nothing you type is sent to us, and there is no sign-up.
Where an input is a judgement rather than a measurement, we say so on the page and let you change it, rather than picking a flattering number on your behalf.
Six calculators are published. The gap we would most like to close is battery payback — and it stays open because we have no sourceable UK price series for storage, in the way that we now have one for solar installation costs. The battery calculator does the sizing arithmetic and stops short of the number we cannot stand behind.
If there is one you were looking for, tell us — it moves up the queue.
Most people start here
What would a rooftop solar system generate and save?
Generation split into what you use and what you export, because those are worth 26p and 4p respectively — the difference most calculators hide.
What does a plug-in solar kit actually save?
Generation by location, mounting angle and orientation, on figures we generated from PVGIS and you can reproduce. Shows its self-consumption assumption instead of hiding it.
Sizing
Money
Sorry to hear that. What was the problem?