Calculate your yearly saving
Move the slider to your monthly bill, add your postcode, and the figures update as you go. Nothing is sent anywhere and nothing is stored: the calculation runs entirely in your browser.
Add a postcode for a regional sunlight figure. Until then a UK average is used.
A battery raises what you save each year, but costs more up front, so the payback period gets longer. Both effects show below.
Your indicative estimate
- Estimated saving a year
- £778
- System size
- 4.5 kWp
- Simple payback
- 8.1 yrs
- CO2 avoided a year
- 838 kg
An indicative estimate from typical UK figures, not a quotation. Your roof, shading, tariff and usage pattern all change it. We confirm the real numbers at survey.
Get an exact quoteEvery number behind that estimate
A savings figure you cannot check is worth nothing. These are the assumptions the calculator uses, and the ones your own survey will replace with real values.
- Electricity price
- We assume 27p per unit. Your own tariff is the single biggest lever on the result: a higher rate makes solar pay back faster, because every unit you generate is one you are not buying.
- Export rate
- We assume 15p per unit exported. Smart Export Guarantee rates vary a lot between suppliers and are not tied to who supplies your electricity, so this is worth shopping once you are live.
- How much you use yourself
- Without a battery we assume you use 35% of what you generate; with one, 65%. A household that is empty all day sits below the first figure, which is why the survey matters more than the calculator.
- Sunlight where you live
- Regional sunlight comes from your postcode area, in five bands between the north of Scotland and the south coast. An area we do not recognise falls back to a UK average rather than guessing a region.
- Installation cost
- Roughly £1,400 per kWp installed, before any battery. Real quotes vary with roof access, scaffold, mounting type and how much cable has to be run.
Questions about the estimate
What the figure does and does not mean.
Get the real figure for your roof.
The calculator gives you the scale. A free survey gives you the real number, in writing.