If your EPC came back lower than you expected, you are not stuck with it. EPCs are produced by a person following a standard methodology, and like any survey they can contain errors or pessimistic assumptions. You have a clear right to challenge an EPC you believe is wrong — and the first steps cost nothing.
This guide explains why ratings come back too low, how to tell whether yours is genuinely wrong, and the exact process to get it corrected.
Why EPCs come back lower than they should
Most "wrong" EPCs are not random mistakes — they come from a handful of predictable causes:
- Assumed (default) values. This is the big one. Where an assessor cannot physically verify something — insulation hidden inside a wall, for example — the methodology requires them to assume the least favourable option. If your walls are insulated but the assessor saw no proof, the calculation may have assumed they are not, dragging your score down.
- Wrong wall construction type. Solid wall versus cavity wall makes a large difference. A misjudged wall type can cost you several bands.
- Missed or under-recorded insulation. Loft insulation depth, cavity fill, or floor insulation that wasn't recorded accurately.
- Incorrect heating or controls. An efficient boiler logged as a less efficient model, or thermostatic controls that weren't credited.
- Wrong age band or floor area. The property's assumed construction date drives many defaults; an error here ripples through the whole result.
The pattern is almost always the same: the assessor recorded a worst-case assumption where they lacked evidence. That is exactly the kind of thing a challenge can fix — if you can supply the missing evidence.
Is your EPC actually wrong? How to check
Before challenging, look at the certificate itself. You can find and download your EPC and read the detailed assessment.
Check the property summary lines for phrases like "assumed", "no insulation", or a wall/heating description that does not match reality. Ask:
- Does the wall type match your property?
- Is your loft, cavity or floor insulation recorded — and at the right level?
- Is your boiler or heating system described correctly?
- Are improvements you have actually made (new windows, insulation, a new boiler) reflected at all?
If you find a clear mismatch between the certificate and the real, evidenced state of your home, you have grounds to challenge.
The step-by-step process to challenge an EPC
Step 1 — Contact the original assessor
Your first step is to go back to the assessor who produced the certificate (their name and contact details are on the EPC). Tell them specifically what you believe is wrong and provide evidence:
- Invoices or receipts for insulation, glazing, or a new boiler
- Building control or installer certificates
- Photographs, or product specifications
If the assessor agrees, the original EPC is cancelled and a corrected one is issued, with the official register updated. There is no charge for correcting a genuine error and no financial risk to you in asking.
Step 2 — Escalate to the accreditation body
If the assessor does not respond, or you are not satisfied with their answer, escalate to their accreditation scheme (such as Elmhurst Energy or Stroma — the scheme is named on the certificate). The scheme is legally obliged to investigate the complaint and, where the information is found to be incorrect, a new EPC must be issued and the register amended. Assessors are required to hold professional indemnity insurance, so there is a proper route to resolution. As a final step you can also report the matter to your local Trading Standards.
Step 3 — Get a second opinion
If you still disagree, you can commission a fresh assessment from a different accredited assessor. This is the one step that has a cost — it is a normal EPC, so expect the usual £60–£120 — but it gives you an independent result. Make sure the new assessor has access to all your evidence so they don't repeat the same worst-case assumptions.
Gather the right evidence first
The whole process hinges on evidence. Before you contact anyone, pull together:
- Insulation proof — installer certificates, cavity wall guarantees (e.g. CIGA), invoices.
- Glazing and door invoices or FENSA/CERTASS certificates.
- Heating — boiler installation certificate, model and efficiency rating, controls.
- Building work — building control completion certificates for extensions or conversions.
An assessor cannot credit what they cannot verify. Supplying this evidence is the single most effective thing you can do to get a fair rating.
When challenging an EPC is worth it
A challenge is most worthwhile when:
- You have clear evidence the recorded data is wrong.
- The correction would move you across a band threshold — for example from D up to C. This matters most for landlords working toward the EPC C requirement by 2030, where the band, not just the score, determines whether you can let legally.
- You are about to sell or remortgage, where the rating affects buyer perception and some lending decisions.
If the correction only nudges your score within the same band, it may not be worth the effort — though fixing the record is still worthwhile if you plan to improve the property later.
Next steps
- Download and read your EPC and look for assumed or incorrect values.
- Gather evidence — invoices and certificates for any insulation, glazing, or heating.
- Contact the original assessor with the specifics; ask for a correction.
- Escalate to the accreditation body if needed — it is free and they must investigate.
- Consider a second opinion from a different accredited assessor if you still disagree, especially if a band change is at stake.
Getting your EPC right is worth the effort: the rating follows your property for up to 10 years and influences its value, its lettability, and your improvement planning.