Our Methodology

1. The Data Source

We utilize the Department for Levelling Up, Housing and Communities (DLUHC) Energy Performance Certificate (EPC) register. This is an open government database containing over 28 million detailed property assessments.

For every postcode district (e.g., "WS15"), we analyze a statistically significant sample of properties to determine the dominant architectural features, specifically filtering for roof-description and total-floor-area.

2. Solar Irradiance Factors

We cross-reference the postcode location with historical solar irradiance data (PVGIS) to determine the average annual sunlight hours (kWh/m²). This allows us to adjust the financial projections; a roof in Cornwall (TR1) will generate approximately 15% more yield than an identical roof in Newcastle (NE1).

3. The Scoring Formula

The final Solar Score (out of 10) is a weighted aggregate of:

• Roof Suitability (60%): The percentage of homes in the district with pitched, non-shaded roof structures.
• Sunlight Hours (30%): The regional generation potential.
• Floor Area (10%): A proxy for roof size and system capacity (kW).