What Is an EPC?
An Energy Performance Certificate (EPC) provides an assessment of a property's energy efficiency. It is produced by a qualified Domestic Energy Assessor (DEA) following an inspection. The EPC shows:
- An energy efficiency rating from A (most efficient) to G (least efficient)
- An environmental impact rating based on CO₂ emissions
- Estimated energy costs based on the current specification
- Recommendations for improvement with estimated cost savings
EPCs are valid for 10 years and are registered on the national EPC register (accessible at find-energy-certificate.service.gov.uk).
When Is an EPC Required?
An EPC is legally required when:
- Selling a property (must be in place before the property is marketed)
- Renting out a property (a current EPC must be available to prospective tenants)
- Constructing a new building (the completed building must have an EPC)
An EPC is NOT required for listed buildings.
Minimum EPC Rating for Rental Properties
Since April 2020, privately rented properties in England must have an EPC rating of E or above to be let. A property with an F or G rating cannot legally be let unless a valid exemption is registered.
Important upcoming change: The government has indicated an intention to raise the minimum EPC requirement for rental properties to C by 2030 (private rented sector). If this is implemented, a significant proportion of London's older housing stock will need improvement works. Landlords should begin planning now. Note that policy in this area has been subject to revision — always check the current government position.
Typical London EPC Ratings
London's housing stock is dominated by Victorian and Edwardian terraced houses with solid brick walls, suspended timber floors, and single-glazed sash windows. These properties typically rate D or E without significant improvement works.
New-build flats and houses typically rate B.
What Affects the EPC Rating?
The EPC is based on an assessment of:
- Roof and loft insulation
- Wall insulation (or lack of it)
- Floor insulation
- Window type and glazing
- Heating system and controls
- Hot water system
- Renewable energy systems (solar panels, heat pump)
- Age and construction type of the property
The DEA does not measure actual energy use — they use standard assumptions about occupancy and heating patterns to produce a standardised assessment.
How to Improve Your EPC Rating
High-Impact Improvements
| Improvement | Typical Rating Improvement | Typical Cost |
|---|---|---|
| Loft insulation (if not already present) | 5–10 points | £300–£600 |
| Cavity wall insulation | 3–8 points | £500–£1,500 |
| Double glazing (if currently single) | 3–6 points | £5,000–£15,000 |
| Condensing boiler replacement | 2–8 points | £1,500–£3,000 |
| Air source heat pump | 10–20+ points | £8,000–£15,000 |
| Solar PV panels | 5–15 points | £5,000–£12,000 |
| External wall insulation | 10–20 points | £15,000–£30,000 |
For Victorian Solid-Wall Properties
The biggest challenge in improving EPCs for pre-1919 solid wall properties is the wall U-value. Without external or internal wall insulation, these properties struggle to achieve a C rating. External wall insulation is the most impactful single measure but is the most expensive.
Grant Funding
Several government and energy company schemes provide funding for energy efficiency improvements:
- Great British Insulation Scheme (GBIS): Insulation measures for properties with EPC ratings D–G
- Energy Company Obligation (ECO4): Targeted at lower-income households for insulation and heating improvements
- Boiler Upgrade Scheme: Provides a £7,500 grant toward air source heat pump installation
Check current eligibility criteria as schemes are updated regularly.
RCB Design & Build
RCB advises on energy improvement measures as part of wider refurbishment projects, helping clients identify cost-effective improvements that will genuinely move the EPC rating — rather than marginal changes that have little impact on the assessment.