How to improve an EPC rating from E to C

Start with your own EPC

Find your certificate on the EPC register and note the exact score. A home on 54 needs 15 points. A home on 39 needs 30, which is a much bigger project.

Read the recommendations next. The Energy Saving Trust says they are usually shown in order of cost-effectiveness. Each step shows the rating you could reach, and that figure usually assumes the steps above it are done, so a single step lower down the list will not achieve it alone.

Look at the potential rating too. If it stops short of C, the assessor's list alone will not get you there. The GOV.UK energy improvement tool gives a second view for homes in England and Wales. If your EPC is several years old or work has been done since, get a new assessment before you spend much.

Why an E is rarely a one-job fix

An E usually means at least one large weakness, and often two. Look at the feature table on your EPC for lines marked poor or very poor. The common ones are uninsulated walls, a thin or empty loft, an old non-condensing boiler, poor controls and expensive heating such as older electric systems.

The Energy Saving Trust estimates that about a third of the heat in an uninsulated home escapes through the walls and about a quarter through the roof. So in most E-rated homes, the walls and loft decide how far you can go. The heating then decides how much the remaining heat costs, which matters because the rating is cost based.

A typical order of work

1. Fix leaks and damp, and check ventilation. Insulating over a moisture problem can make it worse.
2. Insulate the loft to at least 270mm. This is usually the cheapest large gain if the loft is empty.
3. Fill the wall cavities if your walls have unfilled cavities and an installer confirms they are suitable.
4. If the walls are solid, decide whether insulation is practical. It is the biggest single decision in this project.
5. Add a programmer, room thermostat and radiator valves if you lack them.
6. Replace an old boiler, or plan a low carbon system, once heat loss has been reduced.
7. Consider solar panels if you still fall short of C.

Homes with cavity walls often have the simpler route, because loft and cavity work are relatively cheap. Solid-walled homes usually need the larger spend, or a decision to stop at D for now.

Typical costs

These are the Energy Saving Trust's typical figures, mostly for a semi-detached home in Great Britain. Costs vary with the home, the region and the installer, so treat them as a starting point and get quotes.

What is unrealistic from E

• Reaching C with low energy lighting and draught-proofing. These are worth doing, but the Energy Saving Trust says LEDs are unlikely to make a huge difference to the rating.
• Starting with windows. A set of A-rated double glazing costs about £4,800 for a semi-detached home and saves about £85 a year compared with single glazing, far less than the walls or loft.
• Assuming a new boiler alone will do it. It can help a lot, but if the heat loss stays high, an E-rated home is unlikely to jump two bands.
• Treating a heat pump as a guaranteed gain. Today's rating is cost based, so the effect depends on the home. Ask an assessor whether they can model it first.

If you rent the home out

E is the current legal minimum for most private lets in England and Wales. The government plans to raise this to the equivalent of C by 1 October 2030, based on a fabric standard plus either a heating or smart readiness standard, with a £10,000 cost cap. This still needs new legislation. Homes rated C on the current scale before 1 October 2029 are due to count as compliant until that EPC expires or is replaced, so fabric work done early is rarely wasted.

Help with the cost

In England, the Warm Homes: Local Grant can fund free upgrades for eligible lower income households in homes rated D to G, where the council has funding. In Wales, Nest may help eligible households in homes rated E or below. The Boiler Upgrade Scheme offers £7,500 towards a heat pump in England and Wales. Government-backed Warm Homes loans can cover heat pumps, solar and batteries. Qualifying energy-saving installations are zero rated for VAT until 31 March 2027, then 5%. ECO4 ends on 31 December 2026, so do not plan around it.