If you have ever wondered what is an EPC beyond a letter from A to G, the short answer is this: it is a standardised assessment of a home’s energy performance, based on details about its construction, heating, insulation and other features.
For landlords, understanding what happens during an EPC survey helps you prepare properly and avoid a surprisingly common problem: useful evidence being unavailable on the day. The assessor does not simply glance at the boiler and make an educated guess. They collect property details using the government’s RdSAP assessment method, record what they can verify, and apply standard assumptions where information is missing.
Here is a practical walkthrough of what they check, and how you can help the visit run smoothly.
Before the room-by-room checks: how the survey works
The assessor starts by building a picture of the property: its age, layout, dimensions, construction and extensions. These details help the assessment software calculate the home’s heat loss and energy performance.
The visit is generally visual and non-invasive. The assessor may use a measuring device, take photographs and ask you questions, but an EPC survey is not a boiler service, structural inspection or general condition report. The aim is to record relevant energy features, not to test every appliance or investigate every hidden cavity.
The more reliable evidence available, the less the assessment needs to rely on standard assumptions. That distinction matters: assumptions are part of the method, but they may not reflect improvements you have made.
1. Entrance, hallway and the property’s overall layout
The assessor records the property type, number of storeys and general layout. They measure relevant dimensions and note the arrangement of the dwelling, including the number of habitable rooms and any spaces that affect the assessment.
They also look for features that change the property’s shape or heat-loss areas, such as an extension, conservatory or unheated space attached to the home. Measurements are not just administrative: property size and form feed into the calculation.
If the property has unusual layouts or several additions, make sure the assessor can see how the spaces connect. A clear route through the home helps them build a more complete picture.
2. Living rooms and bedrooms: walls, windows and heating
In the main rooms, the assessor looks at wall construction and visible signs of insulation. Depending on the property, walls may be solid, cavity, timber-framed or of another construction type. The approximate age and appearance of the building can help inform the assessment, but evidence of later insulation may help establish what is actually in place.
Windows are checked for their glazing type, such as single or double glazing, and the assessor records relevant details about fixed heating. That may include radiators, electric heaters or other systems, alongside visible controls such as thermostats and thermostatic radiator valves.
Fixed lighting is also included. The assessor records the type or proportion of energy-efficient fixed lights. Portable lamps do not count as fixed fittings, so there is no need to stage a parade of table lamps.
If you have certificates or records for replacement windows or insulation work, have them available. What looks obvious to you may not be verifiable from a quick visual check alone.
3. Loft and roof space: insulation and safe access
Where it is safe and accessible, the assessor checks the roof type and looks at loft insulation, including its depth and coverage. If you know when insulation was installed or have paperwork from the work, keep it handy.
Before the visit, clear access to the loft hatch and make sure the area around it is safe to reach. Do not ask an assessor to climb over stored belongings or enter an unsafe space. Nobody benefits from a survey that starts with a balancing act.
If the loft cannot be accessed, the assessor records that limitation and follows the relevant RdSAP conventions. Depending on the available property information, the assessment may use age-based assumptions rather than confirmed insulation details. That does not mean the assessor will automatically assume the loft is uninsulated; it means the final record may be less specific than one supported by direct observation or reliable evidence.
4. Kitchen and utility area: boiler, heating controls and hot water
The assessor identifies the main heating system and notes relevant details such as its type, fuel and controls. They may look at the boiler’s make or model information if it is accessible, as well as a programmer, room thermostat, heating zones or other controls.
They also record how the property’s hot water is provided. This could be through the main heating system or a separate arrangement, such as a hot-water cylinder. Where there is a cylinder, its type, insulation and relevant controls may be noted.
Keep the boiler and cylinder accessible, and point out any controls that are not immediately obvious. Manuals, installation records or other supporting paperwork can help clarify details that cannot be confirmed just by looking.
It is worth being clear about what this check is not: an EPC assessor does not carry out a gas-safety check or test whether a boiler is operating safely. The assessment records energy-related information, not a safety certificate.
5. Extensions and alterations: the details behind the floor plan
An extension can affect the property’s dimensions, construction and heat-loss calculations, so the assessor records relevant details about it. They may note its approximate age, size, walls, roof, windows and relationship to the home’s heating system.
If you have plans, completion paperwork or records of insulation and glazing improvements, gather them before the appointment. The assessor still needs to record and assess the property, but good supporting information can help establish features that are not immediately visible.
The same principle applies to other significant changes. Tell the assessor what has been altered and when, and provide evidence where you can. “We did the back room a while ago” is a helpful start; a dated document is better evidence.
What happens to the information after the visit?
The assessor enters the collected details into approved RdSAP software, which calculates the EPC rating and generates the certificate. The completed EPC is then lodged on the national register, where it receives a unique reference.
Photographs and site notes can support the assessment record. They may show features such as heating equipment, controls, insulation, windows or details that need explanation. These are evidence for the energy assessment, not a photographic condition report.
This is why accuracy on the day matters. If a genuine improvement is visible or supported by reliable evidence, it can be recorded. If an important feature cannot be seen and there is no paperwork to confirm it, the assessment may need to use a standard assumption. The aim is not to chase a particular letter; it is to make sure the property’s recorded details are as complete and accurate as possible.
How to prepare your rental property for an EPC survey
A little preparation makes the visit more straightforward. Before the assessor arrives, make sure you can provide:
- Access to all rooms, including any locked rooms or extensions.
- Safe, clear access to the loft hatch, if there is one.
- Access to the boiler, hot-water cylinder, meters and heating controls.
- Keys for any locked areas the assessor needs to inspect.
- Any previous EPC or records of insulation, window, heating or extension work.
If an area is inaccessible or a detail is uncertain, explain that rather than guessing. The assessor can record what is and is not available and apply the appropriate method. Clear access and useful evidence simply give them more to work with.
A more accurate record starts with a well-prepared visit
An EPC is a calculated assessment built from specific property details, not a general verdict on how comfortable the home feels. For an EPC for rental property, make it easier for the assessor to verify those details: provide access, gather relevant records and flag improvements that may not be obvious.
Evestaff Property Inventory Clerks are accredited members of ECMK. Founded in 2012, Evestaff has more than 12 years’ experience serving landlords, property managers and letting agencies across London and Kent. Our highly experienced clerks use modern technology and meticulous documentation to help protect property assets and tenancy deposits. We take a similarly precise approach to recording the facts: the small details matter, especially when someone needs to rely on the report later.
EPC surveys are one part of the wider picture. Alongside them, we provide residential property services including inventories, check-ins, check-outs, floorplans and inspections for landlords across London and Kent, and we cover a long list of towns through our location pages.
If you are a new customer, you can receive a 10% discount on your first booking. And if a fellow landlord or property professional could use our services, feel free to point them towards our Refer a Friend offer.
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