Display Energy Certificates: which buildings need a DEC?
Updated 19 October 2026 · SEO Dons Editorial
A Display Energy Certificate is required in England and Wales for any building with a total useful floor area over 250 square metres that is occupied by a public authority and frequently visited by the public. The occupier must keep a valid DEC on display where visitors can see it and hold a valid advisory report. A DEC rates how much energy the building actually used, which is what separates it from an EPC.
Which buildings need a DEC?
Regulation 14 of the Energy Performance of Buildings (England and Wales) Regulations 2012 applies to buildings occupied by public authorities and frequently visited by the public. The duty began on 9 January 2013 for larger buildings, and from 9 July 2015 it has covered every such building over 250 square metres. Government guidance says the duty applies to buildings occupied in whole or in part by a public authority.
Three tests decide it, and all three must be met:
- Size: a total useful floor area over 250 square metres, which the regulations define as gross floor area measured in line with RICS guidance.
- Occupier: a public authority occupies the building, in whole or in part.
- Visitors: the building is frequently visited by the public.
For example, a hypothetical 400 square metre council customer service centre with daily walk-in visitors would meet all three. Enforcement guidance is clear there are no exceptions once the criteria are met. The duty follows the occupier, not the owner: private organisations, including those sharing a building with a public body, do not need a DEC, though they may display one voluntarily. The DEC guide's own example is a public authority that lets a building to a private company; no DEC is required because the occupier is private.
How long is a DEC valid?
Validity depends on size, and the certificate and its advisory report run on different clocks in larger buildings.
| Total useful floor area | DEC valid for | Advisory report valid for |
|---|---|---|
| Over 1,000 square metres | 12 months | 7 years |
| 250 to 1,000 square metres | 10 years | 10 years |
Validity runs from the nominated date, which the assessor sets no later than three months after the end of the 12-month period the rating is based on. In practice, a large public building needs a fresh DEC every year, while the advisory report behind it lasts much longer.
How is a DEC different from an EPC?
They answer different questions. An EPC carries an asset rating, based on the energy a building would need under standardised use, given its fabric and services. A DEC carries an operational rating, based on the energy actually consumed while the building was occupied.
| DEC | Commercial EPC | |
|---|---|---|
| What it rates | Actual metered energy use over 12 months | Modelled performance under standard use |
| When it is needed | While a public authority occupies a qualifying building | On construction, sale or letting |
| Who is responsible | The occupier | The builder, seller or landlord |
| Validity | 12 months or 10 years, by size | 10 years |
| Display | Always, in qualifying buildings | Only over 500 square metres, frequently visited, where one exists |
One does not replace the other. Enforcement guidance says that having and displaying an EPC does not mean a building does not also need a DEC, and the reverse is also true. A public building only needs an EPC if it is constructed, sold or let, and the DEC guide adds that where the building has an EPC, its rating must be shown on the DEC. Our guide to whether you need a commercial EPC covers those triggers, and our guide to displaying a commercial EPC covers the separate display rule. The guide to EPCs for care and healthcare buildings covers surgeries, clinics and care homes.
How is the operational rating worked out?
The DEC is based on actual metered energy over the last 12 months. The occupier works with the assessor to gather actual meter readings or consignment notes for all fuels used, and the result is compared with a benchmark for that type of building. A building performing at the typical level for its type scores 100. For buildings over 1,000 square metres, the certificate also shows the operational ratings for the previous two years, where available, so trends are visible to anyone reading it.
A new occupier is treated differently until it has been in the building for 15 months, because a full year of readings may not yet exist.
What does the advisory report contain?
The advisory report lists recommendations to improve the building's energy performance, grouped by payback:
- short term, up to 3 years, such as building energy management measures;
- medium term, 3 to 7 years, such as upgrading building services;
- long term, more than 7 years, such as low and zero carbon technologies.
The occupier does not have to act on the recommendations. But because the next DEC is calculated from metered use, improvements show up in the following year's rating for larger buildings, which is not true of an EPC until a new one is commissioned.
Who produces a DEC, and how is it displayed?
Only an energy assessor accredited to produce DECs can produce the certificate and advisory report, and the assessor must visit the site for the first one. Both are lodged on the national register. The government's find an energy certificate service covers public buildings in England, Wales and Northern Ireland, so you can check a building's current DEC there. Guidance says the displayed certificate should be no smaller than A3.
What are the penalties?
Local weights and measures authorities, usually trading standards, enforce the rules. The DEC guide sets out a penalty charge notice of £500 for failing to display a DEC and £1,000 for failing to hold a valid advisory report, and the documents must still be commissioned afterwards. A notice must be withdrawn if the occupier can show it took all reasonable steps to comply. Where a local authority is itself subject to the duty, enforcement passes to another enforcement authority. These rules cover England and Wales; Scotland and Northern Ireland have separate requirements. If your building needs a DEC, an EPC or both, you can request quotes from accredited assessors through the form on this site; our guide to EPCs for schools, colleges and nurseries covers one of the most common groups of public buildings.
Sources
- A guide to display energy certificates and advisory reports for public buildings, Ministry of Housing, Communities and Local Government, updated 10 August 2015, checked 19 October 2026
- Local weights and measures authority guidance for the enforcement of the requirements of the Energy Performance of Buildings Regulations 2012, Ministry of Housing, Communities and Local Government, updated 17 March 2016, checked 19 October 2026
- Find an energy certificate, GOV.UK, checked 19 October 2026
- The Energy Performance of Buildings (England and Wales) Regulations 2012, regulations 2, 14, 16, legislation.gov.uk (The National Archives), checked 19 October 2026
Common questions
Does a privately run leisure centre or office need a DEC?
Not if the occupier is a private organisation. The DEC duty falls on public authority occupiers, and private organisations, including those sharing a building with a public body, do not need one, although they may display one voluntarily.
Can a public building use its EPC instead of a DEC?
No. Enforcement guidance says that having and displaying an EPC does not remove the need for a DEC, and the reverse also applies. If the building has an EPC, the DEC guide says its rating must be shown on the DEC.
Does the assessor need to visit every year for a large building?
The first DEC and advisory report require a site visit. In later years the DEC guide says they can be based on previous knowledge of the building, provided the same assessor produces them and the occupier declares that nothing has changed.
How is the 250 square metre threshold measured?
The regulations use total useful floor area, defined as gross floor area measured in line with guidance from the Royal Institution of Chartered Surveyors. If your building is close to the threshold, ask the assessor to confirm the measured area.