How an Energy Performance Certificate is Conducted

When you rent or buy a property – either commercial or domestic – you should be given an Energy Performance Certificate (or EPC). This is a document showing the results of an assessment which will have been carried out by a professional assessor and indicates how energy efficient the property is.

Whether you are a landlord, renting a property, or buying or selling one, it is important that at the time that the occupation of the property changes hands, an Energy Performance Certificate is also provided.

The Domestic EPC Assessment Process

When your domestic EPC assessor visits the property, they will look at a number of factors in order to determine the energy-efficiency of the property – and give it an ‘energy rating’. The assessor will need to have access to every part of the property to be able to carry out the assessment properly.

Some of the factors that they will look at include:

  • The size of the property
  • What and how much insulation there is
  • The property construction type
  • The lighting which you have
  • The heating systems in the house and how they are controlled
  • The property’s ventilation

From this information they will then be able to rate the energy-efficiency of the property from A to G – with ‘A’ being the most efficient, and ‘G’ being the least.


The assessor will look at the number of fixed light fittings in the house as well as the number of low energy lightbulbs (CFT, LED or normal fluorescent tube types) that are fitted.


The inspector will have a look in the loft. Although they don’t necessarily need to go inside the loft, they will need to be able to see it to determine how much insulation (if any) is in there and where it is. Currently, the recommendation is to have 270mm at the joists.

The assessor will also look into the loft to try to determine the type of wall that divides your property from your neighbours.


The assessor will then look at the windows of the property to ascertain whether it is single, double, or triple glazed. This can have a big impact on the energy-efficiency of the property. They will check when the glazing was done. If you have BFRC data or a FENSA certificate, this will help them and can be used as evidence.


The inspector will then look at the heating system in the property. It can be useful to have the boiler documentation to hand if you can. They will have a look at some aspects such as the heat controls and time of the boiler, any thermostats, thermostatic radiator valves, and any other heating sources in the house (such as coal, gas coal-effect fires or log fires).

Photos and Measurements

The EPC assessor will take a series of photographs and measurements of the house. The photographs could be of elements of the inside or the outside of the house. This is because the assessors are regularly audited to make sure that they are consistently producing top quality EPC assessments.

They will also take measurements of the dimensions of the property and draw a sketch of the plan of the house showing these measurements.

The assessor is also likely to ask you questions about the construction of the property – including when it was built, details of any additional construction work that has been done, whether the property has had cavity wall insulation, whether you have heat recovery technology or whether you are on a single or double electricity meter.

After the Assessment

After the assessment you will be provided with the Energy Performance Certificate. The certificate will be split into four sections:

  1. Information about the property, the date of the assessment, a reference number and the average energy costs for a property of that house type.
  2. The A-G energy-efficiency rating, as well as an Environmental Impact CO2 rating.
  3. Actions and recommendations which the assessor suggests so that you can improve the energy-efficiency of the building and whether you might be eligible for help through the Green Deal.
  4. A summary of the property’s features and their energy rating based on u-values.

The amount of time that the assessor will spend at your property depends on the size of your property as well as the access that they are able to get to all of the areas of the house.

Although the process of getting an EPC is thorough, as long as you have relatively easy access to all parts of your property, it is not a disruptive process. In addition to being a legal requirement when you sell or rent a property, it can also be a useful tool to improve its energy-efficiency.