Energy Performance Certificates explained
What an EPC records, how the rating is produced, how long it lasts and what an assessor looks for during the visit.
What an EPC actually is
An Energy Performance Certificate records the assessed energy efficiency of a property using the approved government methodology. It gives an efficiency rating band from A to G, an estimate of energy costs, and a list of recommended improvements. Existing certificates can be checked on the GOV.UK "Find an energy certificate" service.
How the rating is produced
The rating is calculated by the approved methodology from the evidence the assessor records on site. It is not a judgement call and it cannot be negotiated. Two similar-looking properties can produce different ratings because of differences in insulation, heating, controls, glazing or the evidence available at the time of the visit.
For the same reason, no assessor can promise a rating in advance. If someone guarantees a band before the assessment, treat that as a warning sign.
How long an EPC lasts
An EPC is normally valid for 10 years from the date it is lodged, unless a newer certificate is produced for the same property. If you have completed works since the last certificate, a new assessment will reflect the evidence available at the time of the new visit.
What the assessor looks at
- Room dimensions and the overall property layout
- Wall, roof and floor construction, and insulation where it can be seen or evidenced
- Heating system, fuel type, controls and hot water provision
- Glazing type and approximate age
- Ventilation and extract provision
- The proportion of low-energy lighting
The assessor takes photographs to support each recorded item. Evidence matters: where a feature cannot be seen or evidenced, the methodology applies a default assumption, which may be less favourable than the reality.
Getting the most from the visit
- Provide access to the loft, meters, boiler and any outbuildings within scope
- Have documentation for insulation, glazing or heating upgrades available
- Tell the assessor about extensions, conversions or unusual construction
- Read the recommendations section — it is the most useful part of the certificate