About Business Solar Calculator
A free, transparent sizing and savings tool for UK businesses considering solar — built on the principle that you should be able to check the maths before anyone asks for your contact details.
Why this site exists
Most "solar calculators" aimed at UK businesses are lead-capture forms wearing a calculator costume: opaque assumptions, results held hostage behind an email field, and numbers tuned to make every roof look like a 3-year payback. The result is predictable — facilities managers and finance directors who distrust every solar number they see, including the genuinely good ones.
This site takes the opposite bet: that businesses are more likely to act on numbers they can interrogate. The calculator runs entirely in your browser, publishes all of its assumptions directly below the tool, makes every one of them editable, and documents the full method on the methodology page. The supporting pages — 2026 electricity prices, regional yields, tax treatment and funding routes — exist so you can check where each default comes from rather than taking our word for it.
Where the data comes from
Cost bands are compiled from real 2026 UK commercial installation pricing across the size range the tool covers, reviewed against quoted projects rather than advertised rates. Yield figures sit in the mid-range of published UK irradiance data and metered output from operating commercial arrays. Electricity rates are drawn from published supplier tariffs and brokered contract data, updated as the market moves. Where a figure is uncertain or site-specific — on-site use percentage above all — the tool makes it an input rather than pretending to know it.
The numbers are deliberately conservative. The 25-year figure assumes flat electricity prices for a quarter of a century and includes panel degradation; the payback figure excludes the Annual Investment Allowance, which improves most real outcomes by roughly a fifth. If the calculator errs, it errs against solar — a calculator that flatters you is worse than no calculator.
How the site is funded
The calculator is free and requires no registration, no email, and no personal data — the maths never leaves your browser. The site is operated by SEO Dons Ltd and earns its keep when visitors choose to request a fixed-price quote through the quote form, which routes enquiries to vetted UK commercial solar installers. That step is always explicit and always yours to take; nothing on this site captures your details passively. Questions, corrections or challenges to any figure: info@businesssolarcalculator.co.uk — corrections genuinely welcome, the tool is only useful while it is right.