How to Challenge an Incorrect EPC Rating

Why Challenge Your EPC Rating?

If your EPC rating seems lower than it should be, it could be costing you money — whether you're selling, renting, or simply paying higher energy bills than your home warrants. The good news is that you have the right to challenge an incorrect EPC, and the process is straightforward if you know the steps.

Energy Performance Certificates are produced by human assessors using the Reduced Data Standard Assessment Procedure (RdSAP). While the methodology is standardised, the data input relies on what the assessor observes — and mistakes happen. Research by the Ministry of Housing, Communities & Local Government (MHCLG) suggests that as many as 1 in 5 EPCs contain at least one error that could affect the final rating.

An incorrect rating can have real consequences. A property rated D instead of C could sell for up to £16,000 less, face higher running cost estimates, and — for landlords — potentially fall foul of the Minimum Energy Efficiency Standards (MEES). If you believe your EPC is wrong, it's worth investigating.

Valid Grounds for Challenging an EPC

Not every EPC you disagree with contains an error. Before starting a challenge, check whether any of these common assessment mistakes apply to your property:

Wrong Property Details

• Incorrect property type: The assessor recorded a mid-terrace when your home is actually end-terrace (which has more exposed walls and different heat loss calculations)
• Wrong floor area: Significant errors in measured floor area affect the energy use calculations
• Wrong number of storeys: A bungalow with converted loft space might be recorded as single-storey when it should be two
• Missing rooms or extensions: Conservatories, loft conversions, and extensions that weren't properly accounted for

Wrong Construction Type

• Solid wall vs cavity wall: This is one of the most common errors. Cavity walls with insulation score significantly better than solid walls. Many assessors assume solid walls for pre-1930s properties when the building actually has early cavity construction
• Wall insulation not recorded: If you've had cavity wall insulation or external/internal wall insulation installed but the assessor didn't record it, your rating will be artificially low
• Roof insulation depth: The assessor may have estimated loft insulation at 100mm when you actually have 270mm — this alone can change your rating by a full band

Wrong Heating System Recorded

• Boiler model or age: A modern condensing boiler scores much better than an older non-condensing model. If the assessor recorded the wrong boiler type or couldn't find the model, they may have used default (worse) assumptions
• Heating controls: Programmable thermostats, thermostatic radiator valves (TRVs), and smart heating controls all improve the rating. If these weren't recorded, your score suffers
• Renewable energy systems: Solar panels, heat pumps, or solar thermal systems that were installed but not included in the assessment

Wrong Glazing

• Single vs double glazing: If the assessor recorded single glazing when you have double or triple glazing, this significantly impacts the rating
• Age of glazing: Newer double glazing (post-2002) scores better than older double glazing. The assessor may have used the wrong age category

Common scenario: You had cavity wall insulation installed in 2019, but the EPC assessment in 2024 recorded "no insulation" because the assessor couldn't see evidence of drill holes or didn't check the Cavity Insulation Guarantee Agency (CIGA) database. This single error could drop your rating by 1–2 bands.

Step-by-Step: How to Challenge Your EPC

Most Common EPC Errors (With Real Examples)

Based on data from accreditation schemes and MHCLG audit reports, these are the errors that most frequently lead to incorrect ratings:

Example 1: Cavity Wall Misidentification

A 1935 semi-detached in Sheffield had its walls recorded as "solid brick" when the property actually had cavity construction with blown insulation installed in 2018. The Cavity Insulation Guarantee Agency (CIGA) certificate proved the insulation was present. The EPC was corrected from band E (score 42) to band C (score 71) — a jump of 29 SAP points.

Example 2: Missing Solar Panels

A detached house in Bristol had a 4kW solar PV system installed in 2020. The EPC assessment in 2023 failed to record the panels, resulting in a band D rating. After the challenge, the corrected EPC showed band B — a two-band improvement that added significant value to the property.

Example 3: Boiler Downgrade

A mid-terrace in Manchester had a 2021 Worcestor Bosch Greenstar condensing boiler, but the assessor recorded a "non-condensing gas boiler" — likely because they didn't check the boiler plate or the Product Characteristics Database (PCDB). Correcting this moved the rating from D (58) to C (72).

How Long Does a Challenge Take?

The timeline depends on which stage resolves your issue:

If your challenge is time-sensitive — for example, you're selling and need an accurate rating for marketing — the quickest option may be to simply commission a new EPC from a different assessor. This costs £50–£80 but gives you a fresh, independent assessment within days. The new EPC replaces the old one on the register. Read more about EPC costs.

What Happens if Your Challenge Succeeds?

If the challenge results in a correction:

• A new EPC is issued with the corrected data and (potentially) a new rating
• Same 10-year validity: The new certificate is valid for 10 years from the date of the original assessment (not from the correction date)
• The register is updated: The corrected EPC replaces the old one on the official EPC register
• No cost to you: If the accreditation scheme orders a correction, the assessor bears the cost
• You can use the new rating immediately: For marketing, MEES compliance, or any other purpose

Important: A successful challenge doesn't guarantee your rating will improve. If the only error was minor (e.g., wrong glazing age but still double-glazed), the corrected data might not change the overall band. The SAP calculation uses hundreds of data points, and some have more impact than others.

How to Gather Evidence for Your Challenge

The stronger your evidence, the faster your challenge will be resolved. Here's what to collect:

• Installation certificates: FENSA certificates for windows, Gas Safe certificates for boilers, CIGA certificates for cavity wall insulation, building control sign-off for loft insulation
• Invoices and receipts: From contractors who carried out improvement work, showing the date and specifications
• Photographs: Clear photos of your boiler model plate, loft insulation, wall construction (if visible), glazing units, and heating controls
• Manufacturer data: Product specifications for your boiler, heat pump, or solar panels — especially the model number
• Previous EPCs: If you had an older EPC that correctly recorded features the new one missed, this is strong evidence
• Building plans: Original plans or survey reports that show wall construction type

Check the CIGA Guarantee Checker for cavity wall insulation records, and the FENSA register for window installation records. These databases hold records of certified work that your assessor may have missed.

Alternative: Just Get a New EPC

Sometimes the simplest solution is to skip the complaints process and commission a new EPC from a different, reputable assessor. This is worth considering when:

• You're in a hurry (selling or letting the property soon)
• The original assessor is uncontactable
• You've made genuine improvements since the last assessment
• You want a fresh set of eyes on the property

A new EPC typically costs £50–£80 and can be arranged within a few days. The new certificate replaces the old one on the register and is valid for 10 years from the new assessment date.

When booking a new assessment, look for assessors with good reviews who are thorough. Provide them with all your evidence (installation certificates, boiler model numbers, etc.) before the visit so they know what to look for.

How to Prevent EPC Errors in Future

When you next have an EPC assessment, take these steps to ensure accuracy:

1. Prepare documentation in advance: Have all installation certificates, invoices, and guarantee documents ready for the assessor
2. Be present during the assessment: You can point out features the assessor might miss, such as insulation hidden behind plasterboard or underfloor heating
3. Provide access: Make sure the assessor can access the loft, check the boiler model plate, and see all rooms. Restricted access leads to "assumed" values, which are usually worse
4. Check the draft: Some assessors will let you review the data before lodging the EPC. Ask for this and check the key details (wall type, insulation, boiler, glazing)
5. Keep your own records: Maintain a folder with all home improvement documentation. This makes future assessments more accurate and challenges easier if needed

Frequently Asked Questions