How accurate is an EPC?
An EPC is a standardised assessment of a home’s energy performance, not a measurement of that household’s actual bills. Its usefulness depends on recorded features, evidence and assessment assumptions; there is no single established accuracy percentage.
By EPC Benchmark · Last reviewed
What the rating measures
The assessment uses standard occupancy and modelled energy use so homes can be compared consistently. For existing dwellings, RdSAP uses assumptions to reduce the information that must be collected. The assessor records what can be inspected and supported by acceptable documents; hidden insulation may therefore appear as assumed. An assumed entry is not, by itself, proof of an error.
What a difference may mean
| Situation | Useful check |
|---|---|
| Actual bills differ | Household use and tariffs differ from the model’s standard assumptions. Check the certificate’s purpose before treating bills as evidence of an error. |
| Work happened after assessment | The certificate describes the home as recorded earlier. Discuss whether a fresh assessment is appropriate. |
| A specific feature seems incorrect | Check the current official record and relevant evidence, then contact the assessor. |
| The score is below a district average | Peer position is context, not proof that the certificate is wrong. |
Review the certificate itself
Check the assessment date and current official record, then review the property details, heating, fabric descriptions and whether entries are based on evidence or assumptions. EPC Benchmark does not collect these details and cannot validate or correct an individual certificate.
In a fictional example, a homeowner sees an assumed insulation description and has installation paperwork. They ask the assessor to review whether that evidence is relevant. Acceptance, a changed score or a different band is not guaranteed.
Use comparison as context only
EPC Benchmark shows four separate comparisons: all homes in the postcode district; homes of the same property type in that district; homes in the same construction-age band in that district; and homes of the same property type and construction-age band across England and Wales. The two local attribute views are separate: the site does not combine district, property type and age into one comparison group. They do not validate an individual EPC. Checking the certificate comes first; an aggregate comparison is secondary context.
To see what a score range means before comparing, read the guides to an EPC rating C, EPC rating D or EPC rating E.
If you suspect a specific recorded error, read how to raise it with the assessor and accreditation scheme.
Sources
- GOV.UK: A guide to energy performance certificates — Assessment and evidence guidance; last updated 11 December 2017.
- GOV.UK: Standard Assessment Procedure — Current methodology overview; updated 8 June 2026.
- GOV.UK: Energy performance certificates technical notes — Accreditation, quality assurance and data limitations; updated 30 July 2026.
Related guides
Read how to challenge a suspected error
Use the official assessor and accreditation-scheme route when a specific entry may be wrong.
Read how to challenge a suspected error