Your EPC rating affects energy bills, mortgage rates, rental legality and property value. Here is exactly which upgrades deliver the most improvement — and what Government funding is available to help pay for them.
An Energy Performance Certificate (EPC) rates your home from A (most efficient) to G (least efficient). It is produced by a Domestic Energy Assessor and valid for 10 years. EPC ratings matter because they affect your energy bills, mortgage rates (green mortgages for A/B homes), rental legality (minimum E for landlords in England and Wales) and eligibility for Government grants.
| Upgrade | Typical EPC point gain | Typical cost | Grant available? |
|---|---|---|---|
| Heat pump (replaces gas boiler) | 20–40 points | £10,000–£18,000 | BUS: £7,500 / £9,000; WH:LG |
| Solar panels | 10–20 points | £5,000–£11,000 | WH:LG (38% of installs) |
| Loft insulation (uninsulated) | 10–15 points | £300–£600 | ECO4; WH:LG |
| External wall insulation | 10–20 points | £8,000–£25,000 | ECO4; WH:LG |
| Cavity wall insulation | 5–10 points | £400–£800 | ECO4; WH:LG |
| Double/triple glazing | 3–8 points | £5,000–£12,000 | Limited |
| Heating controls / smart thermostat | 2–5 points | £150–£600 | ECO4 in some cases |
Moving from EPC D (55–68 points) to C (69–80 points) typically requires gaining 5–25 points. The cheapest route for most homes:
If your loft has less than 100mm of mineral wool, topping up to 270mm can gain 10–15 points for under £600 — often free through ECO4 or WH:LG.
If your home was built 1930–2000 with unfilled cavities, filling them adds 5–10 EPC points at £400–£800 — often free through ECO4.
A smart thermostat and TRVs add 2–5 points at low cost and improve the heating efficiency score in the SAP assessment.
After any improvements, get a new EPC (£60–£120). This updates your record and may unlock green mortgage products with lower rates.
The most impactful improvements are loft insulation, cavity wall insulation, heat pump installation and solar panels. A Domestic Energy Assessor can tell you which measures score highest for your specific property.
Heat pump installation typically delivers the biggest single EPC improvement, often moving a property from D to B. Solar panels, loft and cavity wall insulation also deliver significant improvements.
Yes. Solar panels can improve an EPC rating by 10–20 points, typically moving a property up one or two bands. They score well in SAP because they generate zero-carbon electricity on-site.
Yes. WH:LG, ECO4 and the Boiler Upgrade Scheme all fund improvements that improve EPC ratings. WH:LG requires EPC Band D or below.
Loft insulation: £750–£900 (EST, May 2026). Cavity wall: £750–£900 (EST, May 2026). Solar panels: £5,000–£11,000. External wall insulation: £8,000–£25,000. Grants can cover some or all costs for eligible households.