EPC (Energy Performance Certificate)
A rating that shows how energy-efficient a property is, graded from A (most efficient) to G (least efficient), required when selling or renting a property in the UK.
An EPC (Energy Performance Certificate) is a document that rates the energy efficiency of a property on a scale from A (most efficient) to G (least efficient). It also includes an estimate of energy costs and recommendations for improvements that could raise the rating. In the UK, an EPC is legally required when you sell, rent, or build a property.
What an EPC tells you
An EPC contains two ratings:
- Current energy efficiency rating — how the property performs today
- Potential energy efficiency rating — what it could achieve if the recommended improvements were made
It also lists:
- Estimated annual energy costs for heating, hot water, and lighting
- Specific recommendations ranked by cost-effectiveness (e.g., loft insulation, double glazing, boiler upgrade)
- The environmental impact rating (CO2 emissions)
How renovation affects your EPC
Many common renovation improvements directly boost your EPC rating:
| Improvement | Typical EPC impact |
|---|---|
| Loft insulation (270mm+) | Significant |
| Cavity wall insulation | Significant |
| Double or triple glazing | Moderate |
| Boiler upgrade (condensing) | Moderate to significant |
| Improving air tightness | Moderate |
| Internal or external wall insulation | Significant |
| Addressing thermal bridges | Moderate |
| Solar panels | Significant |
| LED lighting throughout | Minor |
If you are renovating anyway, check your current EPC recommendations — you may be able to make cost-effective energy upgrades while the walls are open and trades are on site.
When you need a new EPC
An EPC is valid for 10 years. You will need a new one if:
- You are selling the property and the existing EPC has expired
- You are letting the property (minimum E rating required since 2018, with proposals to raise this)
- You have made significant energy improvements and want the rating updated
EPC and the building envelope
The EPC assessment focuses heavily on the building envelope — walls, roof, floor, windows, and doors. Improving these elements during a renovation typically has the biggest impact on your rating. Cosmetic changes (new kitchen, bathroom refurbishment) do not affect the EPC unless they include energy-related upgrades like better extraction or improved hot water systems.
A qualified domestic energy assessor carries out the EPC survey. They inspect the property, record construction details and heating systems, and input the data into approved software that generates the rating. The assessment typically takes 30-60 minutes and costs between 60 and 120 pounds.