From the 1st January 2009, all public buildings with a gross internal floor area greater then 100m2 are required to display a Display Energy Certificate in a prominent place clearly visible to the public. This requirement is a consequence of the transposition into Irish legislation of Article 7(3) of the Energy Performance in Building Directive.

The DEC for large public buildings is calculated as an operational rating, where the actual energy consumed in the building is compared to a benchmark for buildings of the same type, and shown on the certificate A-G scale in terms of primary energy. There is also a CO2 indicator which shows the CO2 emissions associated with the buildings energy consumption.

The information required to carry out the rating consists of the gross internal floor area of the building and records of the total energy used in the building (e.g. electricity bills, gas bills, meters etc) over a recent 12 month period.