EPC C for London Rental Properties: What the Target Means, Qualifying Improvements and Landlord Cost Exposure

The Policy Trajectory

The government consulted on raising the minimum Energy Performance Certificate rating for privately rented properties from E to C in England and Wales. Under proposals that have been under consideration since 2020, new tenancies would be required to meet EPC C first, followed by all tenancies. While implementation dates have shifted as successive governments have reviewed the policy, the direction of travel is established and London landlords with properties rated D or below are advised to plan ahead rather than wait for confirmed mandation dates.

The current minimum is EPC E. Properties rated F or G cannot legally be let unless a valid exemption has been registered. An EPC C requirement would affect a substantial proportion of London's rental stock, given the age and construction type of the borough's housing — Victorian and Edwardian terraces, 1930s semis and post-war estates that were not built with modern insulation standards.

How EPC Ratings Are Calculated

An EPC is calculated using the Standard Assessment Procedure (SAP), which takes into account the fabric of the building (wall, roof and floor insulation), the heating system type and efficiency, hot water provision, lighting, and renewable energy generation. The output is a score from 1 to 100 mapped onto a letter band from G (1–20) to A (92–100). Band C spans 69 to 80 points.

The most impactful variables in a SAP assessment are heating system efficiency and wall insulation. In London, where solid wall construction (pre-cavity wall) dominates the Victorian and Edwardian stock, the heating system upgrade is often the most cost-effective route to a higher rating.

Qualifying Improvements: What Raises an EPC Score

The most common measures that move a property up the EPC bands:

• Boiler replacement — replacing a G-rated non-condensing boiler with an A-rated condensing combi typically adds 8 to 15 SAP points, often the single largest uplift available. In London properties with old floor-standing cast iron boilers, this improvement is frequently sufficient on its own to move from E to D, and combined with other measures can reach C.
• Loft insulation — adding 270mm of mineral wool in an uninsulated loft typically adds 6 to 10 SAP points. Cost is relatively low at £300 to £600 for a typical terraced house. Where loft insulation is already present but below 100mm, topping up to 270mm still contributes meaningful points.
• Solid wall insulation — the most expensive and impactful improvement for London's pre-1920 stock. External wall insulation (EWI) typically adds 10 to 20 SAP points but costs £8,000 to £20,000 depending on property size and specification. Internal wall insulation (IWI) is less disruptive to the external appearance and may be required in conservation areas but reduces floor area.
• Double or triple glazing — replacing single-glazed sash windows with double-glazed units contributes 3 to 8 SAP points. In conservation areas, slim double-glazed units or secondary glazing can be acceptable alternatives.
• Smart heating controls — adding a room thermostat, thermostatic radiator valves and a programmer where none exist contributes 1 to 3 SAP points at low cost.
• Heat pump installation — an air source heat pump replacing a gas boiler can add significant SAP points because the SAP methodology credits heat pumps' coefficient of performance. However, heat pumps require additional fabric improvements to perform efficiently and are most suitable for larger properties with space for external units.

Boiler Upgrade Schemes and Grants

The Boiler Upgrade Scheme (BUS) provides grants for replacing gas boilers with heat pumps: £7,500 for air source heat pumps and £7,500 for ground source heat pumps as of current scheme rates. The scheme is available to landlords as well as homeowners, subject to the property having a valid EPC with no outstanding loft or cavity wall insulation recommendations.

The Great British Insulation Scheme targets properties in lower EPC bands and is available to landlords where the tenant household qualifies on means-tested benefits grounds. For London landlords with older stock, this can substantially reduce the cost of loft and wall insulation improvements.

Expected Cost to Reach EPC C: London Scenarios

• Victorian terrace (1880–1910), currently D, gas heating — boiler replacement (£2,500 to £3,500) plus loft insulation top-up (£300 to £500) and smart controls (£200 to £400) will typically reach C. Total: £3,000 to £4,400.
• Edwardian flat (ground floor), currently E, non-condensing boiler — boiler replacement alone may reach D. Achieving C typically requires solid wall insulation costing £5,000 to £12,000 for the relevant wall area, depending on the approach and access constraints in an occupied flat.
• Post-war semi or terraced house, currently D, cavity walls — cavity wall insulation (£700 to £1,500) plus boiler upgrade is usually sufficient to reach C. Total: £3,500 to £5,000.

The Cost Cap and Exemptions

Under current policy proposals, a cost cap of £10,000 per property was proposed, above which a landlord could register an exemption if the works needed to reach EPC C would exceed that figure. The exemption requires registration with the PRS Exemptions Register and must be renewed every five years. Landlords should not rely on the exemption route as permanent protection — policy changes are possible, and an exemption does not prevent tenants from raising the EPC as a habitability issue under the Homes Act.