ESOS Overview & Glossary

Energy Savings Opportunity Scheme (ESOS) information

• Summary of ESOS

• ESOS Guidance (Environment Agency) - Comply with the Energy Savings Opportunity Scheme (ESOS): phase 3

• ESOS Regulations 2014 (Legislation) and Amendments (2023)

Lead Assessor competencies and process:

• PAS 51215:2014 (withdrawn but current) - Energy efficiency assessment. Competence of a lead energy assessor. Energy Approach follows this PAS.

The below PAS documents specify the assessment and reporting process that can be used on a voluntary basis for ESOS compliance in Phase 4. 

• PAS 51215-1:2025 - Energy and decarbonisation assessment - Process Specification

• PAS 51215-2:2025 - Energy and decarbonisation assessment - Competencies of lead assessors and assessment teams. 

ESOS Glossary

The Energy Savings Opportunity Scheme (ESOS) uses specific legal terminology defined in the underlying legislation, SI 2014/1643 and SI 2023/1182. Understanding these terms is essential for participants navigating their compliance obligations.

Use the search bar to look up any term. Definitions are drawn directly from the Regulations and updated to reflect Phase 4 requirements.