How much can an EPC rating realistically improve?

A poorly insulated house with an old boiler can move two bands with loft insulation, cavity fill and a new boiler. A house that already has all three has much less headroom without solid wall insulation or solar.

Can I dispute an EPC rating I think is wrong?

Yes. Raise it with the assessor first — if data was recorded incorrectly, the certificate can be amended. If that does not resolve it, the assessor's accreditation scheme has a formal complaints process.

Does a new kitchen or bathroom affect the EPC?

No. Cosmetic improvements are not part of the assessment at all.

EPCs

How to improve your EPC rating — what actually moves the score

Not every energy improvement moves an EPC score, and some of the cheapest changes move it more than the expensive ones. Here is what counts.

6 min read · Last reviewed 2026-08-14

How the score is actually calculated

An EPC rating is not a measure of how much energy you use. It is a modelled estimate of the cost of heating, lighting and providing hot water to the property, based on standard occupancy. That is why an empty house and a house with five people in it get the same rating, and why changing your habits does nothing to the certificate.

The model weights the building fabric and the heating system heavily. Anything that reduces modelled heat loss, or makes the heat you buy cheaper per unit, moves the number. Anything else mostly does not.

Improvements that reliably move the rating

Ranked roughly by points gained per pound spent for a typical UK home:

Loft insulation topped up to 270mm — cheap, quick, and one of the largest single gains on an under-insulated house
Cavity wall insulation, where the property has a fillable cavity — a substantial jump, often a full band
Replacing an old non-condensing boiler with a modern condensing one, or a heat pump
Full heating controls: a room thermostat, a programmer and thermostatic radiator valves. Cheap, and the model rewards them
Hot water cylinder insulation, or replacing an uninsulated cylinder with a factory-insulated one
Low-energy lighting throughout — small per fitting, but it is one of the cheapest points on the list
Solar PV, which reduces modelled purchased energy and can lift a rating significantly
Solid wall insulation, internal or external, where there is no cavity. Expensive, but for a solid-wall terrace it is often the only route out of an E

Improvements that disappoint people

Replacing already-double-glazed windows with newer double glazing typically gains very little — the model sees both as double glazing. Draught-proofing, smart thermostats and new radiators also tend to move the score barely at all, even though they can make the house noticeably more comfortable and cheaper to run in reality.

This is worth saying plainly: a change can be good for your bills and near-invisible on the certificate. If your goal is the rating specifically, target fabric and heating source.

Get the assessment right, not just the house

Assessors are required to record what they can see and verify. Where they cannot, they must apply assumed values from a standard table, and those assumptions are deliberately cautious. Homeowners routinely lose points on work that has genuinely been done, simply because there is no evidence of it.

Before the visit, gather anything that documents the fabric and plant: cavity wall insulation guarantees, loft insulation receipts, FENSA or CERTASS certificates for windows, boiler installation and Gas Safe paperwork, solar panel commissioning documents, and any building control completion certificates for extensions. Provide access to the loft hatch, the boiler, the cylinder and the meters.

Working out what is worth doing

Every EPC comes with a recommendations report listing suggested measures, their indicative cost and the rating they would produce. That report is the cheapest planning tool available to you, and most people never read past the first page.

If you are improving a property specifically to get over the E threshold for letting, or to hit a target band for a green mortgage, ask the assessor to talk you through which combination of measures gets there. That conversation is usually more valuable than the certificate itself.

Get an EPC quote

How to improve your EPC rating — common questions

How much can an EPC rating realistically improve?: A poorly insulated house with an old boiler can move two bands with loft insulation, cavity fill and a new boiler. A house that already has all three has much less headroom without solid wall insulation or solar.
Can I dispute an EPC rating I think is wrong?: Yes. Raise it with the assessor first — if data was recorded incorrectly, the certificate can be amended. If that does not resolve it, the assessor's accreditation scheme has a formal complaints process.
Does a new kitchen or bathroom affect the EPC?: No. Cosmetic improvements are not part of the assessment at all.