About Business Solar Calculator

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

The calculator’s defaults are indicative planning assumptions. They are not quotes, and they are not measured results from a particular set of projects or arrays. Cost bands per kWp, regional yields and electricity rates are published here so you can challenge them: check the cost bands against real quotes, the yields against a tool such as the European Commission’s PVGIS, and the unit rate against your own bill. 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. You can see all of this in the commercial solar calculator.

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 tax. The Annual Investment Allowance relieves the cost in year one, but the saving is taxed as well, so payback in years moves little; the payback calculator shows the after-tax figures. If the calculator errs, it errs against solar — a calculator that flatters you is worse than no calculator.

Who runs the site and what happens to an enquiry

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. An enquiry sent through the quote form reaches us by email and we reply by email. We do not currently pass enquiries to an installer; if that changes we will name the partner here and in the privacy policy first. Sending an enquiry is always your choice; nothing on this site captures your details passively. Questions, corrections or challenges to any figure: contact the site or email info@businesssolarcalculator.co.uk — corrections genuinely welcome, the tool is only useful while it is right.