EPC guide 01
How to read an Energy Performance Certificate
An EPC is a standardised snapshot of a home’s energy performance. It is useful for comparing the fabric and services of homes, but it is not a survey, bill forecast or substitute for advice tailored to the building.
Start with the rating, then read the detail
Domestic EPCs use an A to G band, where A is the most efficient and G is the least. The band is based on a model of the building’s construction and fixed services, such as heating, hot water, ventilation and lighting. It is an asset rating: it describes the property’s likely performance under standard assumptions, rather than the way one household happens to live in it.
The headline number is helpful for comparison, but it should be the beginning of your reading. A similar rating can arise from very different homes. A well-insulated flat with electric heating and a larger house with a modern boiler may land in the same band for different reasons. The construction, heating and recommendation sections explain the story behind the score.
What the number and band mean
The Energy Efficiency Rating is commonly shown as a score out of 100 and grouped into bands. In the current domestic scale, A is 92–100, B is 81–91, C is 69–80, D is 55–68, E is 39–54, F is 21–38 and G is 1–20. A move of one or two points is not necessarily a meaningful change in comfort or bills; look instead at the measures and assumptions that would create the change.
The score is related to modelled energy costs, so it is not a direct measure of carbon, actual consumption or the quality of an installation. Energy tariffs, weather, household size, room temperatures and how long the home is occupied can all make real bills differ from the figures on a certificate.
A useful reading order
- Check the address, assessment date and floor area describe the home you mean.
- Read the construction and heating details before drawing conclusions from the band.
- Review recommendations in the context of condition, access, permissions and budget.
- Use the potential rating as a scenario, not a promise of a result.
Read the property features carefully
The certificate records features observed or inferred by the assessor: wall type, insulation, roof, floor, windows, main heating, hot water and lighting. These entries are often more actionable than the headline rating. For example, a note that insulation is “assumed” is different from a record that it was observed, and an older certificate may not include later work.
Treat unfamiliar descriptions as prompts to investigate. Check paperwork, inspect areas you can safely see, and ask an appropriate professional where the answer affects a purchase or retrofit decision. Do not rely on an EPC to confirm the condition, safety or compliance of a boiler, wiring, ventilation system or insulation installation.
Why the potential rating needs context
The potential rating assumes that the cost-effective measures listed in the certificate are installed. It is not a quote, a specification or evidence that every measure is right for the home. A solid-wall house, a flat with leasehold restrictions, or a listed building can require a different approach from the modelled pathway.
Use the potential rating to start a conversation about options. Ask what sequence keeps the building dry and well ventilated, what fabric work should happen before changing the heating system, and whether any permissions or specialist surveys are needed. Our guide to using EPC recommendations explains how to make that conversation more practical.
Check the date and source
A domestic EPC can normally be used for up to ten years, unless a newer certificate has been issued for the same home. That does not mean an older record captures today’s fabric or services. If you have improved the property, are putting it on the market, or need a current picture for a project, consider whether a fresh assessment is worthwhile.
EPC Checker displays data from public sources for research. For the formal record or to arrange a new assessment, use the official government service and an accredited assessor.