Methodology

Proposal reviews

Reviews are currently produced by a human analyst and a technical reviewer working through a fixed checklist covering system specification, price, generation assumptions, self-consumption, savings assumptions, lifetime costs, scope, warranties, installer facts and payment terms. See how we review for the full workflow.

Independent generation estimates

Where we have enough site information (location, orientation, tilt, shading), we compare a proposal's claimed generation against an independent estimate from PVGIS (EU Joint Research Centre). If we don't have enough information to do this responsibly, we say so rather than showing a number.

The calculator

The commercial solar calculator produces wide, indicative ranges from general UK solar planning assumptions — not a proprietary dataset and not a substitute for a site survey or an installer's own design. Every range shown states the assumption behind it. Some of these assumptions are placeholders pending direct market research (see our sources page) and are marked as such.

Tax and policy content

We do not provide tax or legal advice. Where a page discusses capital allowances, business rates or similar topics, treatment depends on the specific business, its ownership structure and how the project is financed — always confirm current rules on GOV.UK or with a qualified adviser.

Corrections

If you spot an error, tell us via our corrections page. We record what changed and when.