Energy Savings Opportunity Scheme

Improving business performance through energy efficiency

Companies who fall within the scope of ESOS are required to undertake an energy audit conducted or overseen by an approved ESOS Lead Assessor unless the organisation is fully covered by ISO 50001. Audits must be conducted every four years. The first deadline was 5 December 2015, the second was 5 December 2019 and the next deadline will be 5 December 2023.

The EI runs one of the biggest registers of qualified ESOS lead assessors – experienced professionals to help your business get the most out of its energy spend, providing advice you can trust.

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What is ESOS?

ESOS is the UK’s response to Article 8 of the European Commission’s Energy Efficiency Directive. It aims to cut carbon emissions by requiring the thousands of large businesses that operate in the UK to measure their energy consumption and identify measures that could be implemented to achieve energy savings.

Visit our guide to ESOS to find out about this mandatory energy assessment scheme, including what it means for your organisation and what actions you will need to take.

What is ESOS?

Have more questions? Download the Frequently Asked Questions for the most common questions about ESOS compliance and regulations answered.


Find an ESOS Lead Assessor

The EI has two listings of energy efficiency professionals who are approved to act as ESOS Lead Assessors, the Register of Professional Energy Consultants (RPEC), and our listing of Chartered Energy Managers approved as ESOS Lead Assessors. You can use these to find an experienced energy efficiency profession who can work through the ESOS process with you and help you identify real energy efficiency savings.

All professionals on our listings required to hold Chartered status and follow a strict Code of Conduct (link), so you can be sure that your organisation will get the best energy advice and that the services you receive are up-to-date, timely and professional.

Register of Professional Energy Consultants

The following Chartered Energy Managers are approved to act as ESOS Lead Assessors and offer their services to businesses.

ESOS approved Chartered Energy Managers available to third parties

The list of In House Lead Assessors lists those Chartered Energy Managers who are approved to act as ESOS Lead Assessors within their own organisation. Some have moved into consultancy roles and may be available to be contracted to perform ESOS assessment on a consultancy basis.

ESOS approved In-House Chartered Energy Managers

Become an ESOS Lead Assessor

Interested in joining our registers?

There are two routes to becoming an ESOS Lead Assessor with the EI –

  • By qualifying as a Chartered Energy Manager through the EI and demonstrating that you meet the PAS standards
  • By joining RPEC, the Register of Professional Energy Consultants, our expert register for those who specialise in energy efficiency advice

All our lead assessors are required to demonstrate a minimum of two years’ good quality professional energy assessment and energy audit experience relevant to the PAS 51215 capabilities which must be related to energy used in a commercial setting, industrial processes or transport operations.

Click the tabs below to find out more about each route.

The ESOS Toolkit

The EI’s ESOS toolkit is designed for those undertaking ESOS audits. This toolkit can be used by anyone working towards ESOS compliance, whether you are an ESOS Lead Assessor or are working within a company preparing to appoint an assessor.

The toolkit includes:

  • Tool A: Overview and introduction – A guide to ESOS and the toolkit
  • Tool B: Total Energy Consumption tool – It allows user to collate energy data for a Company or Group in either units of energy cost, energy consumption or distance, and produce a view of the total energy profile
  • Tool C: ESOS Audit Templates – It outlines the scope, content and output of a best practice ESOS Audit
  • Tool D: Life Cycle Cost Analysis tool – It allows the user to collate data from scenarios and determine the life cycle cost analysis of business as usual verses an investment in new equipment
  • Tool E: ESOS Commercial considerations – It provides advice for consultants entering into an agreement with a client to conduct ESOS work. (May also be useful from a client point of view when hiring a consultant.)
  • Tool F: EU EED Article 8 – A guidance note covering the transposition of the Energy Efficiency Directive (EED) Article 8 across Europe.

For more information, watch our webinar: A guide to using the ESOS Toolkit


  • EI member: £155 + VAT
  • Non-member: £315 + VAT
  • Special rates apply to EI ESOS Lead Assessors and also those individuals who purchased the 1st version of the toolkit during Phase 1 of the Scheme. Please contact the EI's training team at for further information on discount codes.

10% discount for purchase of five or more toolkits in the same transaction.

ESOS CPD Training Package

The ESOS CPD training package consists of the following 5 online modules:

  • Module 1: ESOS Legislation and Standards
  • Module 2: Energy Saving - Controls and Energy Efficiency
  • Module 3: Energy Saving - Lighting
  • Module 4: Energy Saving - Motors and Drives
  • Module 5: Managing Health & Safety for ESOS Assessors

A short multiple-choice quiz is included at the end of each module.

The training package has also been developed to support EI ESOS Lead Assessors in meeting the annual CPD requirements specified by the Environment Agency. As a requirement of their registration, Lead Assessors must complete 5 CPD hours specifically related to ESOS each year.

Please contact the EI's training team at for further information.

More about ESOS

Phase 3 is just around the corner – the next submission date will be 5 December 2023 and the qualification date for the third compliance period is 31 December 2022. The definition of a large undertaking – the companies that must comply with ESOS – is also changing for phase 3 to include a wider range of companies - any UK company that either employs 250 or more people or has an annual turnover in excess of £44 million, and an annual balance sheet total in excess of £38 million.

For up-to-date information on ESOS, guidance on the scheme, and research so far into compliance and benefits being gained by companies, visit the ESOS pages on the government website

You may also find the following resources helpful

  • Complying with ESOS Guidance: The Environment Agency’s guide to qualification, compliance and notification requirements of ESOS. Download the Guidance
  • ESOS Briefing: A detailed review of the ESOS legislation and its requirements. Download the Briefing
  • ESOS FAQs: The most common questions about ESOS compliance and regulations answered. Download the FAQs
  • ESOS Presentation: slides from our presentation - ‘Preparing for ESOS Phase 2 – Applying the lessons learnt in Phase One’, presented at the 2018 Edie Energy Management Forum. Download the presentation slides
  • SECR Energy Insight: Learn more about the Streamlined Energy and Carbon Reporting framework and how it interacts with ESOS. Access the Energy Insight