Energy Saving Opportunities Scheme (ESOS)

The Energy Savings Opportunity Scheme (ESOS) is a mandatory UK energy assessment scheme that requires qualifying organisations to measure total energy consumption and identify cost-effective energy efficiency opportunities. It is designed to improve energy efficiency, reduce energy costs, and support national carbon reduction targets.

ESOS applies to large UK undertakings and corporate groups that meet the qualification criteria on the ESOS qualification date (the date set for each compliance phase). An organisation qualifies if it employs 250 or more employees or has an annual turnover exceeding £44 million and an annual balance sheet total exceeding £38 million.

ESOS can apply to companies, LLPs, partnerships, unincorporated associations, charities, and some not-for-profit organisations, provided they conduct a trade or business in the UK. Where an organisation is part of a corporate group, ESOS is typically assessed at the highest UK parent level, with the highest UK parent acting as the “responsible undertaking” for compliance and submission of the ESOS notification.

ESOS requires organisations to measure total energy consumption across buildings, transport, and industrial processes, conduct compliant energy audits or equivalent routes (e.g. ISO 50001), and have findings reviewed and approved by a qualified ESOS Lead Assessor before submitting a compliance notification to the Environment Agency.

Organisations may also choose to utilise ESOS rebate and reporting support services, delivered through specialist partners such as EnergyBubble, to identify eligible cost recovery opportunities alongside their compliance and energy efficiency programmes.

ESOS operates in four-year compliance phases, with organisations required to reassess their total energy consumption, undertake compliant energy audits, and submit a compliance notification to the Environment Agency for each phase.

Each compliance phase runs on a fixed cycle, meaning organisations must review and update their ESOS assessment at least once every four years, based on energy data from a continuous 12-month reference period within the phase. During the compliance period, organisations must also submit an ESOS action plan and subsequent annual progress update, in line with the latest regulatory requirements.

Yes. Under the latest ESOS requirements (from Phase 3 onwards), qualifying organisations must produce and submit an ESOS action plan following their compliance notification.

The action plan must outline how the organisation intends to implement energy saving opportunities identified during the ESOS assessment and must be reviewed and signed off by a board-level director (or equivalent senior management).

The action plan must then be submitted via the government’s “Manage your ESOS reporting” system by the specified deadline for the compliance phase.

Following submission, organisations are also required to provide annual progress updates against their action plan commitments in the two subsequent years of the compliance period.

These additional requirements strengthen accountability, improve transparency, and encourage organisations to move from energy audits to demonstrable energy efficiency improvements and carbon reduction outcomes.