The ratings on the certificate provide a measure of the building's overall energy efficiency and its environmental impact, calculated in accordance with a national methodology. It takes into account factors such as insulation, heating and hot water systems, ventilation and fuels used. The average Energy Efficiency Rating for a dwelling in England and Wales is band E (rating 46).

Buildings that are more energy efficient use less energy, save money and help protect the environment.

From 6th April 2009 any dwelling offered for sale prior to its completion will require a Predicted Energy Assessment. This measures the predicted overall energy efficiency and Environmental impact of the home based on the initial build (walls, roof, windows, floor etc) and engineering specification (heating, hot water etc)