The initials can make two very different documents sound interchangeable. A Display Energy Certificate, or DEC, reports how a qualifying public building has actually used energy. An EPC describes a building's modelled energy efficiency under standardised conditions. Choosing the wrong document can leave a real compliance gap.
Who falls into the DEC regime?
A DEC is generally required for a building above 250 m² of useful floor area that is occupied in whole or part by a public authority and frequently visited by the public. Think about who occupies and uses the building, not just its architectural type. An accredited assessor can confirm whether a particular site qualifies.
Why energy records matter
The DEC operational rating draws on measured consumption, so twelve months of relevant energy data, floor area and occupancy context are central to the exercise. It is accompanied by an advisory report. A commercial EPC instead models expected energy performance from building features. A building can therefore have different stories to tell through the two documents.
Plan for the next renewal
For a qualifying building over 1,000 m², the DEC lasts one year and its advisory report seven years. Between 250 m² and 1,000 m², both last ten years. Keep a record of your expiry dates and data sources. If you manage a public estate, start with a building-by-building review rather than assuming one certificate covers every address. Our Display Energy Certificate service can help scope the next assessment.