Why did our Display Energy Certificate rating change?
Read a public building’s operational energy rating in the context of meters, occupancy and building use.
A DEC describes energy used in operation
A Display Energy Certificate, or DEC, is based on a public building's measured energy use rather than only a model of its fabric and systems. Its operational rating compares adjusted consumption with a benchmark for the building type. That makes it a useful prompt for questions about how a building is run, but a changed letter band does not by itself prove that the walls, windows or plant have improved or deteriorated. The government DEC guide describes the calculation and the accompanying advisory report.
Check the period and the meters first
Gather the electricity, gas and other fuel data used for the certificate. Confirm the dates covered, whether readings were actual or estimated, and whether a shared meter includes space outside the assessment boundary. A missing bill, a changed supply or a new sub-meter can distort a year-on-year comparison if the difference is not explained. The assessor should be told about anomalies rather than asked to make undocumented adjustments. A clear meter schedule helps the facilities team understand what the new rating represents and supports the next assessment.
Look at how the building was used
Opening hours, occupied floor area, building use and the services operating during the period can change. A leisure building with longer hours, for example, may use more energy even if its plant is unchanged. Conversely, a partially occupied building may use less energy without becoming intrinsically more efficient. The DEC method allows certain adjustments, but the accredited assessor must apply the approved methodology, not an informal explanation from the occupier. Keep a record of major changes such as a new tenant, extended public opening, additional equipment or a significant refurbishment.
Compare the advisory report with the trend
The advisory report identifies possible energy improvements; it is not a certificate that the measures have been carried out. Use it to separate low-cost operational actions from capital works, then compare bills and meter trends after any change. A year of lower consumption might reflect better controls, milder conditions, reduced activity or several causes at once. Ask the assessor which inputs explain the movement in the operational rating. This helps a public-sector property team avoid claiming savings that the evidence cannot support.
Prepare the next DEC with a cleaner data trail
Maintain a single record of meter identifiers, bills, floor-area changes, occupancy notes, certificate references and advisory-report dates. Check the existing DEC on the government public-building certificate service before commissioning another. Our guide to DEC requirements and renewal explains when a public building must display a certificate. Our Display Energy Certificate service uses a bespoke quote so the building, data availability and advisory-report requirement can be discussed together.