Data Sources / Methodology

How we compute postcode-level estimates for system size, generation, savings, and payback — and which datasets we use.

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How we estimate

• Roof fit: Typical usable area per dwelling type for each outcode.
• Generation: PVGIS yield (kWh per kWp) adjusted for losses and typical orientation.
• Savings: Ofgem regional unit rates and standing charges applied to a typical load profile.
• Payback: System cost bands (with/without battery) divided by annual savings.

Assumptions & caveats

• Figures are indicative; property specifics (orientation, shading, roof condition) vary.
• Tariffs, export rates, and equipment choices affect outcomes.
• Datasets and models update; we refresh periodically.

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: Current electricity unit rates and standing charges by region.
• GOV.UK / MCS statistics: Real-world installation cost bands from certified installers.
• EPC Open Data: Local housing context (aggregated; never address-level).

Reproducibility

We keep the calculations consistent across all outcodes. Key assumptions are shown on each page. If you spot anything off, please contact us.