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esos assessment

How to perform an ESOS Assessment in 7 easy steps

| Alex Dovey |

What is ESOS?

The Energy Savings Opportunity Scheme (ESOS) is a UK energy legislation for meeting the EU Energy Efficiency Directive Article 8. ESOS came into force on 17 July 2014. ESOS is a mandatory compliance scheme for large organisations that met qualifying criteria with the goal of reducing EU energy consumption by 20% by 2020. ESOS compliance occurs every 4 years in four yearly phases and requires regular energy audits that help large businesses conserve energy. We are currently in ESOS Phase 3.


Those who are new to ESOS regulations and compliance will benefit from the following breakdown of these 7 steps on how to conduct an ESOS assessment.

1. Calculate Total Energy Consumption

All the energy that a business consumes needs to be calculated accurately. This includes energy usage for:

  • Sites (buildings/land/property)
  • Industrial and manufacturing processes
  • Transport

All fuel types are included in ESOS and there are no exemptions. Therefore you’ll need to measure your consumption of all your different energy types including:

  • renewables
  • heat
  • combustible fuels
  • electricity/gas
  • any other form of energy

You are only responsible for the energy you consume and not any energy that may be supplied, for example tenants renting part of a site or property you own will be metered and they are responsible for the energy they consume not you.

Within transport calculations you only include the price of fuel you have purchased directly or where your employees have purchased fuel and claiming it back for work reasons. Therefore, public transport and company travel by air and rail is excluded.

Consumption data is taken from 12 consecutive months that includes the qualification date but not the compliance date.

2. Select 90% of your consumption for audit

An ESOS assessment requires 90% of your total energy consumption to be audited. This leaves 10% of your energy consumption that you can be excluded and the energy that you choose to exclude is known as ‘de minimis energy consumption.’ which can take the form of a utility, site, multiple sites, or production activity.

3. Determine the Lead Assessor’s involvement

ESOS Lead Assessors can support at different stages of the ESOS assessment and their level of support may vary.

They can support with the collection and calculation of energy data for the assessment or verifying your reports and calculations, including a review of your de minimis determination.

They can also support at the energy audit stage, and it’s typical for a Lead Assessor to conduct the audit, although they do not have to but they would need to approve that your audit is compliant with the minimum requirements.

It is more common for the lead assessor to perform both of the above activities as their expertise and knowledge will be fully utilised. Even if the determined lead assessor is an internal employee or external energy consultant, they would have needed to be fully certified by the government approved professional body register.

4. Conduct the ESOS Energy Audit and Identify consumption reducing strategies

The next step is to conduct an energy audit for any energy not covered by ISO 50001, a Display Energy Certificate, or a Green Deal assessment. This ESOS energy audit is on the data you have collected and excludes the de minimis energy you’ve identified.  

Your selected sites will be surveyed using energy consumption profiling which involves breaking down the different ways in which energy is used by activities and assets, and analysing any variations in energy use to identify inefficiencies. This can be done with energy management and consumption software.

The UK Government guidance states that ESOS audit data must:

  • be for a continuous period
  • be for energy generated by your organisation, even if this was excluded from your previous calculations
  • cover 12 consecutive months of data, which must fall within 24 months prior to your compliance date
  • not include data already submitted from previous phases of the ESOS scheme


Make sure your data is accessible to the individual conducting your site visits or audits. This will allow them to focus on the identification of potential energy efficiency measures.

It is worth getting the ESOS audit right the first time as the more accurate the data and analysis conducted will result in better insights in your consumption to come up with energy saving recommendations.

5. Create a consumption report and identify energy efficiencies

Once the audit is complete, a consumption report can be generated that your lead assessor will use to create a plan for compliance with strategies to reduce energy consumption.

6. Sign Off On Your Compliance

When your ESOS assessment has been completed, board level director(s) will traditionally review the report and approve the documentation which signs off on your ESOS compliance. The report is submitted to the Environmental Agency (EA) via their online portal and a copy is maintained in case of an audit by the EA. At this stage you have now complied as you can evidence the necessary requirements of the analysis and energy audit.

7. Implement Energy Saving Recommendations

The final step, and one that doesn’t have to be performed to comply to ESOS, is the actual implementation of the energy saving recommendations to reduce your consumption. Technically this is not mandatory for ESOS compliance (just conducting the ESOS assessment ticks the regulatory box) but it would be foolish not to implement the recommendations as they will reduce your energy spend and help your to recoup the cost of the assessment. In addition to the financial benefits, implementing those efficiencies demonstrates your efforts to support Net Zero strategies publicly and will benefit your brand and image.


If your business needs support with your ESOS compliance contact us to speak to an energy consultant.