The Public vs. Private Sector Divide
There is significant confusion among building operators regarding Display Energy Certificates (DECs) and Energy Performance Certificates (EPCs). While they both use an A-G scale, they measure completely different metrics. One is about the 'Asset' (the building's potential), while the other is about the 'Operational' use (how the occupants actually use it). This article clarifies the legal requirements for public buildings and why private sector landlords are increasingly adopting 'Voluntary DECs'.
What is a DEC?
A Display Energy Certificate (DEC) measures the actual energy consumed by a building over a 12-month period, based on meter readings. An EPC, by contrast, is a theoretical model of the building's potential efficiency. DECs are legally required for public authority buildings over 250m² that are frequently visited by the public.
The 'Operational' Rating vs. the 'Asset' Rating
A building could have a high-spec EPC (Grade A) but a poor DEC (Grade G) if the heating is left on all weekend or the BMS is poorly configured. This 'Performance Gap' is a major focus for UK building services in 2026.
Legal Requirements and Validity
We detail the validity periods:
Over 1,000m²: DEC is valid for 1 year; the Advisory Report is valid for 7 years.
250m² to 1,000m²: DEC and Advisory Report are valid for 10 years.
Why Private Landlords Want DECs
ESG-conscious tenants (especially in the London 'Grade A' office market) now demand proof of operational performance. We explore how DECs provide the data needed for GRESB and carbon reporting.
Conclusion
If the EPC is the 'Blueprint,' the DEC is the 'Utility Bill.' Understanding the interplay between the two is essential for any facility manager aiming for true sustainability.