Display Energy Certificate
Display Energy Certificates (DECs) show the actual energy usage of a public building (the
operational rating) and allow the public to see the energy efficiency of a building. This is
based on the energy consumption of the building as recorded by gas, electricity, and other
meters. The DEC should be displayed at all times in a prominent place visible to the public.
How a DEC is calculated
A DEC Assessor calculates the DEC rating using actual energy consumption over one year. This may
include different fuel types, electricity, and district heating and cooling. Operational rating is
calculated from meter readings or energy bills.
If you don't have enough billing data, a DEC can be carried out using an estimate from your energy
supplier. A DEC must be updated every year to reflect energy-use trends.
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Do all buildings require a DEC?
DECs are only required for buildings that have a total useful floor area of more than 500m2 (floor
area will be reduced to 250m2 on 9 July 2015) that are occupied by a public authority or an
institution providing a public service to a large number of people and are frequently visited by
members of the public. DECs are valid for one year. The accompanying advisory report is valid for
Advice and guides on DECs for public buildings
The requirement to obtain and display a DEC came into effect on 30 December 2008.
Where a building is partly occupied by a public authority or a relevant institution, the authority
or institution is responsible for displaying a DEC and having a valid advisory report. Other private
organizations occupying the building, irrespective of the size they occupy, do not need to display a
Advice and guides for unmetered and campus DECs
Although multiple small buildings on campus where each building is less than 500m2 are excluded, if
these buildings are linked to one another by a heated space or are served by the same heating or
cooling system then a DEC is required. The energy consumption for each separate building will then
be derived by proportioning based on floor area.
Every building for which a DEC is required must display its own individual DEC. Where metering is at
the site level the DEC must be based on the metered site energy demands but with the consumption
apportioned to each building on an area-weighted basis. Where different benchmarks apply to the
buildings on the site, for example, a school building and a swimming pool building, then the
relevant benchmark category for the building should be selected.
After December 2009 it is expected that sub-meters have been installed where required.
How do I get a DEC?
An energy assessor, accredited to produce DECs for that type of building, is the only person who can
produce a DEC and advisory report for your building.
The assessor in line with the approved method will review the fuel and energy consumption data you
provide. Adjustments may be made for occupancy, the intensity of use, special energy uses, weather,
For the DEC the carbon dioxide emissions are based on the energy consumption and total useful floor
area and building type, giving a measured CO2 emission per square meter.
The assessor will use the approved calculation methodology to produce a DEC and an advisory report.
The DEC will need to be lodged in a national register by the assessor and given a unique reference
What does a DEC contain?
A DEC must contain the following information:
the operational rating (the building as used) and the
asset rating (the building as built, if available) as determined by the
the operational ratings and CO2 emissions for the
previous two years.
a reference value such as a current legal standard or
A description of the type of accommodation.
Exact measurements of the rooms.
The operational rating is not required where an occupier has been in occupation for less than 15
months. The asset rating is not required in the DEC where an occupier entered into occupation of the
building before 31 December 2008.
The DEC will also show the unique certificate reference number, the address of the building, the
total useful floor area of the building, the name of the energy assessor, their employer (or trading
name if self-employed), the name of their accreditation scheme and the date when the DEC was issued.