What is the cheapest way to improve EPC rating?

The cheapest EPC improvements are loft insulation (£300-£700, typically gains 1-2 rating bands), cavity wall insulation (£500-£1000 via grants), LED lighting (£50-£100), and draught-proofing (£200-£400). These together can lift an F-rated property to D for under £2000.

How much does it cost to improve EPC from E to C?

Improving from EPC E to C typically costs £3000-£8000 depending on property type. This usually requires loft and cavity wall insulation (£1000-£2000), a new A-rated condensing boiler (£2000-£3500), and double glazing or secondary glazing (£2000-£5000 for a typical 3-bed house).

How to Improve EPC Rating: Practical Steps from G to C

Improving your EPC rating reduces energy bills, increases property value, and for landlords, ensures compliance with the minimum EPC E requirement.

The most cost-effective EPC improvements are loft insulation to 270mm (£300-£700), cavity wall insulation (£500-£1000), upgrading to an A-rated condensing boiler (£2000-£3500), and installing double glazing (£3000-£6000). Together, these can lift a property from EPC F to EPC C for approximately £6000-£9000.

Last reviewed: 2026-07-22 | 7 min read | Verified against 4 sources

Quick Wins (Under £1000)
Insulation Upgrades
Heating System Improvements
Windows and Doors
Solar and Renewables

Quick Wins (Under £1000)

Start with low-cost improvements that deliver immediate EPC point gains:

Loft Insulation (270mm): £300-£700, +5 to +15 EPC points
Cavity Wall Insulation: £500-£1000 (grants available), +10 to +20 points
LED Lighting: £50-£100, +1 to +3 points
Draught-Proofing: £200-£400, +2 to +5 points

Loft Insulation

Adding or topping up loft insulation to 270mm depth is the single most cost-effective improvement. Most pre-2000 properties have 50-100mm or none at all. Mineral wool costs £4-£6 per square metre, and a typical loft (40-50m²) costs £300-£500 for materials plus £200-£400 for professional installation.

Cavity Wall Insulation

Properties built 1920-1990 with unfilled cavity walls can gain 10-20 EPC points from cavity wall insulation. The UK government ECO4 scheme covers the full cost for low-income households and offers partial grants for others. Without grants, expect £500-£1000 for a typical 3-bed semi.

LED Lighting

Replace all bulbs with LED equivalents (£2-£5 per bulb). This is scored in the EPC and adds 1-3 points depending on property size. Total cost for a 3-bed house: £50-£100.

Draught-Proofing

Seal gaps around doors, windows, loft hatches, and pipework. Professional draught-proofing (£200-£400) typically adds 2-5 EPC points and reduces heating bills by 5-10%.

Insulation Upgrades

Solid Wall Insulation

Pre-1920 solid-wall properties cannot have cavity insulation. Instead, fit external wall insulation (EWI) or internal wall insulation (IWI):

External wall insulation: £8000-£15000 for a 3-bed house, +15 to +25 EPC points. Requires planning permission in conservation areas.
Internal wall insulation: £4000-£8000, +12 to +20 points. Reduces room size by 50-100mm per wall.

ECO4 grants can cover £4000-£6000 of the cost for eligible households.

Floor Insulation

Suspended timber floors can be insulated from below if accessible, or by lifting floorboards and adding insulation between joists. Cost: £800-£2000 for a ground floor. EPC gain: 3-8 points.

Heating System Improvements

Boiler Replacement

Replacing a G-rated boiler (pre-2000, efficiency below 70%) with an A-rated condensing combi boiler (efficiency 90-94%) adds 10-15 EPC points. Cost: £2000-£3500 installed. Boiler Upgrade Scheme grants offer £7500 for heat pumps, but only £150 for boilers (as of April 2026).

Heating Controls

Install a smart thermostat (Hive, Nest, Tado) with room-by-room zoning. EPC assessors score heating controls, and upgrading from basic timer-only to smart TRVs with weather compensation can add 3-5 points. Cost: £200-£400.

Windows and Doors

Double Glazing

Replacing single glazing with A-rated double glazing (Low-E glass, argon-filled, U-value 1.4 W/m²K or better) adds 8-12 EPC points. Cost for a 3-bed semi: £3000-£6000 for uPVC, £6000-£12000 for timber sash. Partial replacement (just front-facing windows) gives half the benefit at half the cost.

Secondary Glazing

Cheaper alternative for listed buildings or conservation areas where double glazing is not permitted. Magnetic or sliding secondary glazing costs £150-£300 per window installed. EPC gain: 4-8 points (less than full double glazing but still significant).

Solar and Renewables

Solar PV Panels

A 4kW solar PV system (10-12 panels) costs £5000-£7000 and adds 10-15 EPC points. The EPC calculation assumes all generated electricity offsets grid consumption. Payback: 8-12 years via reduced bills and SEG export payments.

Air Source Heat Pump

Replacing a gas boiler with an air source heat pump (ASHP) can add 15-25 EPC points, particularly in well-insulated properties. Cost: £10000-£14000 minus £7500 Boiler Upgrade Scheme grant = £2500-£6500 net. However, running costs can be higher than gas in poorly insulated properties, so insulate first.

Related Guides

Sources

Energy Saving Trust, "Typical costs and savings for energy efficiency improvements," updated June 2026. Accessed 22 July 2026.
National Insulation Association, "Loft Insulation: Costs and Specifications," 2026 edition. Accessed 22 July 2026.
Building Research Establishment, "Domestic Energy Model (SAP 10.2): Boiler Efficiency Ratings," 2021. Accessed 22 July 2026.
Department for Energy Security and Net Zero, "Solar PV: EPC Credit Calculation," GOV.UK guidance, April 2026. Accessed 22 July 2026.

Last reviewed: 2026-07-22