EPC Ratings Explained

The headline rating on EPCs is called the Energy Effciency Rating (EER).

Calculation of this rating is based on the modelled annual running costs of the property, which include:

• Space Heating
• Water Heating
• Lighting
• Ventillation
• Pumps & Controls

These are known as regulated energy costs

'Regulated' in this context doesn’t infer price controls, but rather means energy uses that are included and controlled within the EPC calculation methodology.

These costs are modelled under fixed assumptions so that different dwellings can be fairly compared, regardless of how occupants actually use the services within the dwelling.

EPCs deliberately exclude energy that depends heavily on occupant behaviour such as:

• Cooking appliances
• TVs, computers, and electronics
• Plug-in devices
• Portable heaters
• Refrigeration

These are called unregulated loads and are not part of EPC energy cost calculations.

The modelled annual running costs of the dwelling are related to the floor area of the dwelling as an Energy Cost Factor (ECF) via the following equation:

Then the ECF is used to calculate the EER as follows:

If the ECF is greater than or equal to 3.5 then:

Or otherwise, if it is less than 3.5:

In the assessment software, this rating is calculated to 4 decimal places and then rounded to the nearest integer.

For ratings with a fractional component of 0.0001 to 0.4999 it is rounded down.

For ratings with a fractional component of 0.5000 to 0.9999 it is rounded up.

This is the final integer rating that we are used to seeing and it is deemed to fall within a certain band, depending on its value as follows: