Independent solar numbers for your postcode using official UK data
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Data sources and methodology

How we compute postcode-level estimates for typical system size, generation, savings, and payback, and which datasets we rely on.

SolarByPostcode is designed for UK household decision-making. We do not model your exact roof or your exact address, but we aim to be transparent, consistent, and conservative about the assumptions we use.

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What we model (and what we do not)

  • We model typical outcomes: postcode-level estimates intended to be directionally correct for normal homes in that area.
  • We do not model your roof: we cannot see exact orientation, shading, roof condition, or usable area at property level.
  • We do not provide quotes: our purpose is to help you understand the numbers before you speak to installers.

How we estimate

  • Roof fit: typical usable area per dwelling type for each outcode, used to derive plausible system size bands.
  • Generation: PVGIS yield (kWh per kWp) by location, adjusted for typical UK losses and realistic performance (so results are not “perfect lab output”).
  • Savings: Ofgem regional unit rates and standing charges applied to a simple, typical household load profile. Savings depend heavily on how much generation you use in-home versus export.
  • Payback: cost bands (with/without battery) divided by estimated annual net benefit. This is an indicative payback, not a guarantee.

Assumptions and caveats

  • Property specifics vary: shading, orientation, roof layout, and electrical constraints can move results meaningfully.
  • Tariffs and export rates vary: your supplier, your export arrangement, and your household usage patterns can change outcomes.
  • Battery economics are situational: batteries can improve self-consumption, but they often extend simple payback unless your usage pattern strongly supports them.
  • Refresh cadence: datasets and assumptions change over time. We review and refresh periodically, and we aim to keep methodology consistent across all outcodes.

Primary datasets

  • ONS Postcode Directory (ONSPD): UK postcodes, verified locations, regional boundaries.
  • PVGIS (EU Joint Research Centre): solar irradiance and expected energy yield by location.
  • Ofgem Price Cap: electricity unit rates and standing charges by region.
  • GOV.UK / MCS statistics: installation context and cost ranges from certified-installation sources where available.
  • EPC Open Data: local housing context (aggregated; never address-level).

Where a topic is sensitive to assumptions (for example, export value, self-consumption, or battery sizing), we try to show the trade-off explicitly on-page rather than hiding it in the model.

Reproducibility and feedback

We keep calculations consistent across all outcodes so you can compare areas fairly. Key assumptions are shown on each postcode page. If you spot anything off, or want us to clarify an assumption, please contact us.