Solar system sizing tool
How big a solar system you actually need
This is a free UK calculator. Enter your figures to get an instant, personalised result — no signup, no email capture, no upsell.
Frequently asked questions
What's the average UK solar system size?
4kWp (around 9–10 panels) is the most-installed size, covering ~80% of a typical 4-bed's annual electricity.
Should I oversize for an EV?
Yes if roof allows — extra kWp added for EV charging usually pays back faster per panel because of the high marginal value of self-charging.
Can I fit solar on a small roof?
Modern 22%+ efficiency panels (e.g. Aiko Neostar) need ~5.5m² per kWp. The tool flags whether your roof comfortably fits the recommended size.