A BER is an examination of a building to determine the building's energy demand and energy performance. It creates a comparative scale to measure one dwelling against another on their energy performance scales.

The BER measures in kilowatt-hours per square metre of floor area per year (kWh/m^2^/annum). Determining this usage allows the dwelling to be positioned on the BER rating scale. The scale goes from A1 being the most energy efficient house available all the way to G, the least energy efficient.