Since 1 October 2008 public buildings in the UK over 500m2 must display a Display Energy Certificate (DEC) prominently at all times.
DECs are designed to promote the improvement of the energy performance of buildings. They are based upon actual energy usage of a building and raise awareness about the energy efficiency of public buildings. The certificate looks similar to the energy labels provided on new cars and electrical appliances such as fridges and freezers – it uses a similar scale for energy efficiency, i.e. from A to G with A being the most efficient and G the least.