ECO4 Supplier Data Dictionary
Summary
Ofgem published version 3.0 of the ECO4 Supplier Data Dictionary, updating the templates and field definitions that obligated suppliers use to notify insulation and heating measures under the Energy Company Obligation scheme. This is a routine compliance document for suppliers already delivering ECO4 measures.
Why it matters
ECO4 is a redistributive obligation that socialises insulation costs across all energy bills. Template updates do not change the obligation's scope, cost, or structure.
Key facts
- •ECO4 Supplier Data Dictionary updated to version 3.0
- •Updated 26 March 2026
- •Originally published 17 August 2023
- •Includes project and measure notification templates v1.1
Areas affected
Memo
ECO4 Supplier Data Dictionary | Ofgem Please enable JavaScript in your web browser to get the best experience. BETA This site is currently in BETA. Help us improve by giving us your feedback . Close alert: ECO4 Supplier Data Dictionary Publication type: Guidance Publication date: 17 August 2023 Last updated: 26 March 2026 Scheme name: ECO Show all updates Print this page Share the page Share on Facebook Share on Twitter Share on LinkedIn This guidance document provides information to assist suppliers in completing the ECO4 notification templates for projects and measures. It contains a description of every field on the templates, the acceptable data that may be entered in those fields and the circumstances under which this data should be included. Suppliers should only use the most recent version of the dictionary and templates. The project and measure notification templates are also available on this page. A list of changes in each version of the dictionary document is found in the summary of updates published below. Main document ECO4 Supplier Data Dictionary version 3.0 [PDF, 311.48KB] Subsidiary documents Project notification template v1.1 [CSV, 875.00B] Measure notification template v1.1 [CSV, 490.00B] Summary of Updates to ECO4 Supplier Data Dictionary version 3.0 [PDF, 173.35KB] Print this page Share the page Share on Facebook Share on Twitter Share on LinkedIn All updates 26 March 2026 added updated guidance document and summary of updates. Close