{"id":125,"date":"2026-06-04T11:00:57","date_gmt":"2026-06-04T10:00:57","guid":{"rendered":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/?p=125"},"modified":"2026-06-04T11:01:09","modified_gmt":"2026-06-04T10:01:09","slug":"what-are-decs","status":"publish","type":"post","link":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/2026\/06\/04\/what-are-decs\/","title":{"rendered":"What are DECs?"},"content":{"rendered":"\n<h3 class=\"wp-block-heading\">What is a DEC?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A DEC shows the energy performance of a building based on actual energy consumption as recorded over the last 12 months within the validity period of the DEC (the operational rating).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The operational rating is a numerical indicator of the actual annual carbon dioxide emissions from the building. The various types of energy consumption from occupying a building must be brought together on a common basis so that the performance of one building can be compared with that of another. The UK has decided that the common unit should be CO<sub>2<\/sub>&nbsp;emissions, since this is a key driver for energy policy.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This rating is shown on a scale from A to G, where A is the lowest CO<sub>2<\/sub>&nbsp;emissions (best) and G is the highest CO<sub>2<\/sub>&nbsp;emissions (worst).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">DECs for buildings larger than 1,000m<sup>2<\/sup>&nbsp;also show the operational ratings for the previous 2 years, where available.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/assets.publishing.service.gov.uk\/media\/61682b8dd3bf7f55fa9269f2\/s960_DEC.png\" alt=\"\"\/><figcaption class=\"wp-element-caption\">A display energy certificate<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The operational rating is based on the amount of energy consumed during the occupation of the building over a period of 12 months from meter readings and is compared to a hypothetical building with performance equal to one typical of its type (the benchmark).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Typical performance for that type of building would have an operational rating of 100. A building that resulted in zero CO<sub>2<\/sub>&nbsp;emissions would have an operational rating of zero, and a building that resulted in twice the typical CO<sub>2<\/sub>&nbsp;emissions would have an operational rating of 200. If the building is a net energy generator, it would still be given an operational rating of zero.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The operational rating must be calculated according to the methodology approved by the Secretary of State. This is done by an accredited energy assessor using a software tool for the calculation which has been approved by the Secretary of State. See the&nbsp;<a href=\"https:\/\/www.gov.uk\/government\/publications\/display-energy-certificate-software-specification\">DEC software specification<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The DEC should be displayed in a prominent place that is clearly visible to members of the public. A sample certificate is shown. To enable members of the public to view the document easily, it should be no smaller than A3 in size.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A DEC must be accompanied by an advisory report and the owner of the building must have a valid one available. The advisory report highlights recommendations to improve the energy performance of the building (i.e. its fabric and associated services such as heating, ventilation and lighting).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">What a DEC contains<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A DEC must contain, by law, the following information:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the operational rating as determined by the government approved operational rating methodology<\/li>\n\n\n\n<li>a reference value such as a current legal standard or benchmark<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For buildings with a total useful floor area greater than 1000m<sup>2<\/sup>&nbsp;only, the DEC must also contain:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the operational ratings for the building expressed in any certificates displayed by the occupier during the last 2 years before the nominated date. In buildings where no historic energy consumption data are available, this information will not be complete until the third year of occupation after the introduction of DECs for that type of building as it will be derived from previous DECs<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The DEC will also show the unique certificate reference number under which the DEC has been registered, the address of the building, the total useful floor area of the building, the name and address of the energy assessor, the name of their accreditation scheme and the date when the DEC was issued.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">What an advisory report contains<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The advisory report accompanies the DEC and contains recommendations for improving the energy performance of the building. The advisory report may contain a range of possible improvements, including cost effective measures that may be implemented to improve the energy performance of the property. The report includes zero and low cost operational and management improvements, possible upgrades to the building fabric or services, and opportunities for the installation of low and zero carbon (LZC) technologies.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The report enables the occupier to identify what may be done to improve, for example, building energy management, building services, etc. therefore reducing energy consumption and CO<sub>2<\/sub>&nbsp;emissions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The advisory report categorises the list of recommendations, by payback period as follows:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>short term payback (up to 3 years), for example building energy management measures<\/li>\n\n\n\n<li>medium term payback (3 to 7 years), for example upgrading building services<\/li>\n\n\n\n<li>long term payback (more than 7 years), for example low and zero carbon technologies<\/li>\n\n\n\n<li>each category includes the energy assessor\u2019s selection of the most suitable improvement measures for the building, generally between 5 and 10 measures. The advisory report also includes the energy assessor\u2019s recommendations which may include additional improvement measures, for example measures recommended by a previous energy audit<\/li>\n\n\n\n<li>the advice provided in the advisory report is intended to be for information only. Occupiers receiving an advisory report are advised to seek further detailed professional advice before reaching any decision on how to improve the energy performance of the building<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>What is a DEC? A DEC shows the energy performance of a building based on actual energy consumption as recorded over the last 12 months within the validity period of the DEC (the operational rating). The operational rating is a numerical indicator of the actual annual carbon dioxide emissions from the building. The various types&hellip; <a class=\"more-link\" href=\"https:\/\/www.sterlingaccreditationltd.uk\/blog\/2026\/06\/04\/what-are-decs\/\">Continue reading <span class=\"screen-reader-text\">What are DECs?<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-125","post","type-post","status-publish","format-standard","hentry","category-mhclg-guidance-display-energy-certificates","entry"],"_links":{"self":[{"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/posts\/125","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/comments?post=125"}],"version-history":[{"count":1,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/posts\/125\/revisions"}],"predecessor-version":[{"id":126,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/posts\/125\/revisions\/126"}],"wp:attachment":[{"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/media?parent=125"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/categories?post=125"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sterlingaccreditationltd.uk\/blog\/wp-json\/wp\/v2\/tags?post=125"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}