Why this site exists
UK solar information is scattered across government PDFs, installer marketing pages and outdated blog posts. Most online calculators hide their assumptions, push you towards a quote form, or use figures from years ago.
SolarWatt UK was built to be the opposite: every calculation shows its working, every number links back to an official source, and no tool sits behind an email wall. If you're weighing up solar panels, a home battery or EV charging, you should be able to get a straight answer in under a minute.
Who runs it
SolarWatt UK is run by an independent publisher — not an installer, not an energy supplier, and not a lead-generation agency. That independence matters: we have no reason to inflate savings or steer you towards a particular system size.
We keep the site deliberately small and fast: static pages, no tracking pixels, no accounts, no paywalls.
Our data sources
Every calculator is built on published, verifiable UK data:
| Data | Source | Reviewed |
|---|---|---|
| Electricity import rate | Ofgem default tariff cap (26.11p/kWh, Q3 2026) | Quarterly |
| SEG export rates | Published supplier tariffs (Octopus, E.ON Next, OVO etc.) | Quarterly |
| Regional sun hours | NREL PVWatts / PVGIS / Solar Energy UK | Annually |
| Installation costs | Energy Saving Trust + market surveys | Annually |
| VAT treatment | HMRC 0% rate on domestic solar & storage (to 31 Mar 2027) | Per Budget |
Each calculator page lists its exact formula and assumptions, so you can check our maths rather than take it on trust.
How we make money
Estimates only — nothing on this site is financial, tax or engineering advice. Always get quotes from MCS-certified installers before committing.
Contact
Questions, corrections, data updates or press:
Spotted an out-of-date figure? Tell us — corrections are usually live within 48 hours.