EPC assessment
What happens during an EPC assessment?
Quick answer
During an EPC assessment, an accredited Domestic Energy Assessor visits the property and records its construction, insulation, heating, glazing and lighting. A typical home takes 45–90 minutes. The survey is visual and non-invasive — nothing is damaged — and the certificate is lodged on the EPC register afterwards.
Knowing what to expect from an EPC assessment helps the visit go smoothly and gives the assessor the evidence needed for an accurate rating. This guide walks through what the assessor inspects, how long it takes, what to prepare, and when the certificate appears on the register.
What does the assessor inspect?
The Domestic Energy Assessor (DEA) carries out a visual survey of the whole property. They note dimensions, wall and roof construction, insulation, the heating system and controls, hot water, glazing and lighting.
Where features cannot be seen, the assessor records a default 'assumed' value under the RdSAP method. Showing evidence of hidden measures — such as cavity wall or loft insulation — can change an assumption to a verified input and improve the result.
How long does an EPC assessment take?
Most domestic assessments take around 45 to 90 minutes on site, depending on the size and complexity of the property. Larger or older homes with more rooms and varied construction take longer.
The on-site visit is only part of the job. The assessor then enters the data into RdSAP software and lodges the certificate, so the EPC is usually available a day or two after the visit.
What should I prepare or provide as evidence?
You do not need to do anything special, but a few preparations help the assessor capture verified inputs rather than defaults.
- Provide access to every room, the loft, and any cupboards housing the boiler or controls.
- Have paperwork ready for insulation, a newer boiler, double glazing (FENSA/CERTASS) or solar panels.
- Note the property's approximate age or any extension dates if you know them.
- Make sure the loft hatch and meter cupboards are reachable.
- Mention low-energy lighting and any heating controls fitted.
What are the steps of an EPC survey?
The table below sets out the main stages of a typical assessment, what the assessor does at each, and what evidence helps the rating.
| Assessment step | What the DEA does | What helps the rating |
|---|---|---|
| Measure & sketch | Records room dimensions and layout | Clear access to all rooms |
| Walls & roof | Identifies construction and insulation | Evidence of cavity or loft insulation |
| Heating & hot water | Notes boiler type, age and controls | Boiler manual or installation date |
| Glazing & lighting | Records window type and low-energy bulbs | FENSA/CERTASS glazing certificates |
| Lodgement | Enters data and lodges the EPC | Accurate evidence at every stage |
Is the property tested invasively?
No. An EPC is a non-invasive, visual assessment. The assessor does not drill, lift floors, remove fittings or run energy tests — they observe and record what is present.
Because the survey is visual, the quality of the rating depends on what the assessor can see or evidence. Anything hidden without proof is recorded as an RdSAP default, which can understate the property's true performance.
When is the certificate lodged?
After the visit, the assessor processes the data and lodges the EPC on the national register. It is typically available within one to two working days and is valid for ten years.
Once lodged, anyone can look the certificate up on the EPC register using the postcode or certificate reference.
Related questions
Do I need to be present during the EPC assessment?
Someone with access to the whole property should be present, but it does not have to be the owner. The assessor needs entry to every room, the loft and any meter or boiler cupboards.
Can I improve my EPC score on the day of the visit?
You cannot change the building on the day, but providing evidence of hidden insulation, a newer boiler or double glazing lets the assessor record verified inputs instead of lower default assumptions.
How long is an EPC valid after the assessment?
A domestic EPC is valid for ten years from the date it is lodged. You can commission a new one sooner if you make improvements and want the rating to reflect them.
Frequently asked questions
- Does the EPC assessor damage anything during the survey?
- No. An EPC is a non-invasive visual survey. The assessor records what they can see and any evidence you provide; they do not drill, lift floors or remove fittings.
- How quickly will I get my EPC after the visit?
- Most certificates are lodged within one to two working days of the assessment and then appear on the national EPC register for anyone to look up.
- Can AI-EPC carry out my EPC assessment?
- No. Any official EPC must be assessed on site and lodged by an accredited Domestic Energy Assessor. AI-EPC is AI-assisted: it helps you prepare for the visit and interpret the result, but it never replaces the accredited assessor.
Keep reading
What is RdSAP?
The assessment method behind domestic EPCs, and why your inputs matter.
Read guideEPC ratings A–G explained
What each EPC band means, the SAP scores behind them and what counts as 'good'.
Read guideHow to book an EPC
A simple step-by-step for booking an accredited EPC assessment.
Read guide