A Display Energy Certificate (DEC) shows the energy performance of a building – based upon actual energy consumption. The DEC provides an energy rating for the building on a scale of A to G, where A is the lowest level of CO₂ emissions and G is the highest level of CO₂ emissions.

DEC’s for buildings over 1,000m² also show the operational ratings for the previous 2 years. The operational rating is based on the actual amount of energy used (from meter readings) and the various types of energy consumption are brought together on a common basis – which is recorded as CO₂ emissions.