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Display Energy Certificates (DECs)

There is a legal requirement for DECs to be obtained and displayed publicly in all buildings over 250m2 occupied by a public body/institution that are regularly visited by members of the public. This includes schools and universities, council premises, libraries, sports facilities, theatres and museums, etc.. They are also required for buildings that house operations previously delivered by public bodies but which have been outsourced to a third party but still uses 50+% of public funding to operate.

Display Energy Certificates (DECs) use a rating scheme known as the Operational Rating ‚Äď this uses the actual annual energy consumption of a building. They help the public see the energy efficiency of a building and over time, any improvements or increased use that occurs.

They are based on the metered energy consumption of the building or, in the case of some fuels, the invoices for any fuels delivered in bulk and stored e.g., wood pellets or oil. The DEC must be clearly displayed at all times and be clearly visible to the public. A DEC is always accompanied by a Recommendation Report that lists cost effective measures to improve the energy rating of the building.

Where the building has a total useful floor area of more than 1,000m2

  • The DEC is valid for 12 months and the accompanying Recommendation Report is valid for seven years.
    Where the building has a total useful floor area of between 250m2 and 1,000m2
  • The DEC and Recommendation Report are both valid for 10 years.

The A to G scale for DECs

This is the operational rating for this building. The rating shows the energy performance of the building as it is being used by the occupants, when compared to the performance of other buildings of the same type.

A building with performance equal to one typical of its type would therefore have an Operational Rating of 100.

A building that resulted in zero CO2 emissions would have an Operational Rating of zero, and a building that resulted in twice the typical CO2 emissions would have an Operational Rating of 200.

This rating indicates whether the building is being operated above or below average performance for a building of this type.

See an example.

Exempt properties

There are very few exemptions to public buildings:

  • buildings less that 250m2
  • buildings not regularly visited by members of the public
  • buildings housing operations permanently outsourced that use less than 50% of public funds to operate


The energy assessment needed to produce an DEC is performed by a qualified public building energy assessor registered with an approved accreditation body. The UK Government has set up a publicly accessible central register of Assessors.

The Assessor will visit the property, and examine key items such as wall, floor and loft construction, windows and doors, and all installed building services and controls (heating, cooling, ventilation, air-conditioning, lighting). They will also ask a number of questions about building management and maintenance and establish the hours of use of the building for public access. The exercise is entirely non-invasive (visual only).

Once back in the office, the Assessor inputs the observations into a software program which performs the calculation of energy efficiency. The calculation of the energy rating on the EPC is based on the UK Government’s Operational Rating Procedure (ORCalc).

The accuracy of the recommendations will depend on the inspection standards applied by the assessor. All registered Assessors are audited by their accreditation bodies in order to maintain standards. An MEP Assessor has a high level of skills, maintained by regular CPD training which frequently exceeds the minimum requirement of their accreditation body and usually provides advice and guidance not generally offered by others.

The property occupier will have to pay for the assessment. Typical costs are:

  • Around ¬£300 for a first time assessment of a small/medium sized building but may pay considerably more for larger/complex premises such as a hospital, university or theatre.
  • Around ¬£150 for an annual DEC renewal, which do not normally require a site visit

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