An Energy Performance Certificate (EPC) gives your property a rating from A (most efficient) to G (least efficient) and is required when you sell, let, or build a property. Most people glance at it during a property purchase and then file it away. That's a missed opportunity. The EPC contains detailed information about your property's energy performance and specific recommendations for improvement, many of which are more actionable than they first appear.
What an EPC Measures
An EPC is produced by an accredited domestic energy assessor (DEA) who surveys the property and inputs data into the Standard Assessment Procedure (SAP) calculation. SAP is a methodology developed by the Building Research Establishment (BRE) that models the energy performance of a dwelling based on its fabric (walls, roof, floors, windows), heating system, hot water system, and ventilation.
The result is an energy efficiency rating (A-G) based on estimated energy costs, and an environmental impact rating based on estimated CO2 emissions. Both appear on the certificate. The efficiency rating is what most people focus on; the CO2 rating is what matters for meeting climate targets.
Important caveat: SAP is a model, not a measurement. It uses standard assumptions about occupancy, heating patterns, and behaviour that may not reflect how you actually use your home. Your actual energy bills can be significantly higher or lower than the EPC suggests, depending on your household's specific habits. Use the EPC as a relative measure (is this house efficient or not, compared to similar properties?) rather than an absolute predictor of costs.
The Rating Scale
EPC ratings are assigned as follows:
| Band | Score range | Typical description |
|---|---|---|
| A | 92-100 | New build or highly retrofitted |
| B | 81-91 | Well-insulated modern home |
| C | 69-80 | Reasonable standard; post-2000 average |
| D | 55-68 | Below average; typical pre-1990 home |
| E | 39-54 | Poor; older housing stock with little improvement |
| F | 21-38 | Very poor; significant measures needed |
| G | 1-20 | Extremely poor; often unimproved Victorian or older |
The average EPC rating for English homes is currently around D-C. A property rated C or above is considered to have reasonable energy performance. Properties rated F or G are increasingly regulated.
Landlord Minimum EPC Requirements
For private rented properties, landlords must have an EPC of at least E to let the property legally. Since 2020, this has applied to new tenancies and renewals; since 2023, to all existing tenancies. Properties rated F or G cannot be let (with limited exceptions) without either improving them to E or registering an exemption with the PRS Exemptions Register.
The government has signalled an intention to raise the minimum to C for new tenancies in future years, though the exact timeline has been revised multiple times. Landlords with properties in bands D or E should plan for the eventual cost of achieving C rating, even if the deadline shifts.
Improving Your EPC Rating
Each EPC includes a recommendations section listing the measures that would improve the rating, with estimated costs and savings. The measures are roughly ordered by cost-effectiveness. Common recommendations and their typical EPC impact:
Loft insulation (if none or shallow). The single highest-impact measure for most pre-2000 houses. Can move a D-rated property to C on its own.
Cavity wall insulation. Where applicable, significant improvement in energy rating. Combined with loft insulation, can shift a D to a solid C or low B.
New boiler (condensing). Replacing a G-rated pre-1990 boiler with an A-rated condensing boiler improves both the energy and environmental rating. SAP gives substantial credit for heating system efficiency.
Heat pump. ASHPs score very well in SAP because SAP penalises gas heating more heavily than before 2021 (reflecting the carbon content of gas). Installing an ASHP in a well-insulated house can achieve an A or high B rating even without other major works.
Solar PV. SAP gives significant credit for solar panels, particularly since the 2021 SAP update that increased the weighting for renewable generation. A south-facing 4kWp system can improve a rating by 10-15 SAP points.
Get your EPC updated after significant works. An EPC is valid for 10 years, but if you've made major improvements (new boiler, insulation, windows, solar) since the last assessment, a new EPC will reflect the current performance and is worth commissioning. It supports grant applications, mortgage applications, and is more useful for prospective buyers.
Getting an Assessment
EPCs must be produced by accredited domestic energy assessors. Search at the register on the government's EPC website (epcregister.com) and book directly with an accredited assessor. A standard assessment costs £60-£120. Beware of assessors offering very low prices who may be doing desktop assessments (estimating rather than surveying): a properly done assessment requires the assessor to visit and inspect the property.