The Energy Company Obligation (ECO4) is a government energy-efficiency scheme in Great Britain. Its main objectives are to address fuel poverty and reduce carbon emissions. ECO4 requires energy companies to implement energy efficiency measures in domestic premises. It is not a grant scheme, as the energy companies decide which retrofit projects to fund, the level of funding provided, and the partners they work with.

ECO4 focuses on improving the energy efficiency of the least efficient homes and households in fuel poverty. Only properties in energy efficiency bands D-G are eligible for treatment. The scheme also promotes a comprehensive upgrade of these homes, adopting a multi-measure whole-house retrofit approach. Additionally, a minimum number of privately-owned homes in energy efficiency bands E, F, and G must be upgraded, ensuring that the least efficient homes are addresse

Under ECO4, there is a new Minimum Requirement (MR) that mandates improving the energy efficiency rating of band D and E homes to at least band C, and band F and G homes to at least band D. The scheme aims to incentivize the installation of various energy-efficient measures, including insulation, first-time central heating, renewable heating, and district heating connections.