Energy Savings Opportunity Scheme (ESOS)
ESOS is a mandatory UK energy assessment scheme requiring large undertakings to audit their energy use every four years and identify practical, cost-effective energy efficiency opportunities. It is administered by the Environment Agency.
What is Energy Savings Opportunity Scheme (ESOS)?
The Energy Savings Opportunity Scheme (ESOS) is a UK government scheme introduced under the Energy Savings Opportunity Scheme Regulations 2014 to implement Article 8 of the EU Energy Efficiency Directive. It requires qualifying large undertakings to conduct comprehensive energy assessments every four years and report compliance to the Environment Agency.
An organisation qualifies for ESOS if it meets the Companies Act definition of a large undertaking: at least 250 employees, or annual turnover exceeding £44 million and a balance sheet exceeding £38 million. Corporate groups are assessed as a whole — if the parent company qualifies, the ESOS requirement covers the entire group's UK energy consumption.
ESOS compliance requires organisations to: measure their total energy consumption across buildings, transport, and industrial processes; identify areas of significant energy consumption (covering at least 90% of total energy use); conduct energy audits of those areas or demonstrate compliance through ISO 50001 certification, Display Energy Certificates (DECs), or Green Deal Assessments; identify practical energy saving opportunities; and notify the Environment Agency of compliance by the deadline.
ESOS Phase 3 (compliance deadline: 5 June 2024) introduced significant changes compared to earlier phases. Organisations must now report their total energy consumption and the energy savings opportunities identified. From Phase 3 onwards, there is also a requirement to set a net zero action plan pathway, identify at least one energy intensity ratio, and provide greater detail on the recommendations made.
ESOS does not legally require organisations to implement the identified energy savings — it is an assessment and reporting obligation, not a mandate to invest. However, the scheme is designed to ensure that senior leadership (the "responsible officer," typically a board director) is aware of cost-effective energy efficiency measures available to the organisation. In practice, many organisations find that ESOS audits identify measures with attractive payback periods that they choose to implement.
ESOS audits must be conducted or reviewed by an approved ESOS Lead Assessor registered with an approved professional body. The Environment Agency can issue civil penalties for non-compliance, including failure to notify, failure to maintain records, and making false or misleading declarations.
Practical Examples
A UK manufacturing group with 1,500 employees engages an ESOS Lead Assessor to audit energy use across its 6 factories and 4 offices, identifying £800,000 per year in potential energy savings from LED lighting upgrades, compressor optimisation, and building fabric improvements.
A university qualifies for ESOS and completes its Phase 3 compliance by using ISO 50001 certification for its main campus (covering 70% of energy) and targeted energy audits for satellite sites (covering the remaining 20%+).
A retail chain notifies the Environment Agency of its ESOS Phase 3 compliance, reporting total group energy consumption of 45 GWh and identified savings opportunities equivalent to 12% of consumption from HVAC upgrades and lighting controls.
How Climatise Helps
Climatise's detailed energy consumption data — broken down by site, fuel type, and use — provides the foundation for ESOS audits. The platform's site-level energy analysis helps identify the areas of significant energy consumption that ESOS assessors need to focus on, reducing audit preparation time.
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