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Energy Savings Opportunity Scheme (ESOS)

ESOS is a mandatory energy assessment scheme for organisations in the UK that meet the qualification criteria

Organisations that qualify for ESOS must carry out ESOS assessments every four years. These assessments are audits of the energy used by their buildings, industrial processes and transport to identify cost effective energy saving measures. 

Each assessment is required to provide high quality and targeted advice to large undertakings on cost effective energy efficiency opportunities, which could lead to financial savings. 

Does my organisation qualify for ESOS Phase 2?

You will qualify for ESOS Phase 2, if on 31 December 2018 you are:

1) An undertaking which has 250 or more employees in the UK

2) An undertaking which has fewer than 250 employees, but has: 

  • an annual turnover of €50m and 
  • a balance sheet exceeding €43m

3) Part of a corporate group, which includes an undertaking that meets either criteria (1) or (2) 

If you do not qualify for ESOS Phase 2, you do not have to notify the Environment Agency or Natural Resources Wales.

What is an ESOS assessment?

An ESOS assessment is made up of three parts:

  • A measurement of an organisation or corporate group’s total energy consumption over 12 consecutive months, covering the qualification date of 31 December 2018
  • An audit of at least 90% of the total energy consumption to identify cost effective efficiency recommendations. The audit must be conducted or at least reviewed by an audit “Lead Assessor” who is a member of a professional body approved by the Environment Agency
  • A review of the audit by a board-level director and approval of the audit by the Lead Assessor. For organisations that do not already do so as a matter of routine, ESOS provides a key opportunity to engage with board-level managers on energy expenditure and potential savings

If my organisation qualifies, what next?

Your organisation needs to read the full guidance on ESOS. This will explain  what you need to do over the coming year to comply with the deadline of 5 December 2019. If you don’t already, you must immediately start collecting energy data so you will be ready to comply.

There are no registration forms to complete and no fees payable for participation. However, you must confirm that you have completed an ESOS assessment for your organisation by submitting a notification to the Environment Agency (the UK scheme administrator) by 5 December 2019.  The notification needs to be submitted via an online portal accessed from the ESOS web page under 'Submit your notification of compliance'

What if my organisation doesn't comply?

If you fail to complete an ESOS assessment and/or do not notify compliance by the 5 December 2019 deadline your organisation will be at risk of enforcement action, including the possibility of civil penalties.

Full details of the ESOS Assessment requirements can be found on the ESOS web page. 

How frequently should we complete ESOS assessments?

ESOS will operate in consecutive four-yearly compliance periods.

The next qualification date for ESOS is 31 December 2018, with a requirement to notify compliance by 5 December 2019 (for those who qualify). 

Further information

More detailed guidance on ESOS and how to comply can be found at If you can’t find what you are looking for please email the Environment Agency at regardless of whether your business is in England, Scotland, Wales or Northern Ireland.

For all offshore related queries please email the Department for Business, energy and Industry Strategy at 

What we do

Organisations must notify the Environment Agency by the set deadline that they have complied with their ESOS obligations.

NRW is the compliance body for undertakings registered within Wales. Our role includes:

  • taking steps to monitor compliance with the scheme, including on-site inspections if necessary
  • taking enforcement steps to bring organisations into compliance
  • applying sanctions to undertakings that fail to come into compliance, with proportionate civil penalties

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