The Energy Company Obligation (ECO4) is a government energy-efficiency scheme in Great Britain, designed to tackle fuel poverty and help reduce carbon emissions. ECO is an obligation placed on energy companies to deliver energy efficiency measures to domestic premises. ECO is not a grant scheme; it is up to the energy companies to determine which retrofit projects they choose to fund, the level of funding they provide, and the Retrofit Coordinator and installers that they choose to work with.

ECO4 measures were able to be delivered from the 1 April 2022. The ECO4 scheme will run until 31 March 2026.