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What should you have in your ESOS evidence pack?

Published: 12 February 2024

The new Energy Savings Opportunity Scheme (ESOS) Regulations, as amended in November 2023, now require the completion of an ESOS compliance report and the maintenance of a supporting evidence pack.

Approximately two-thirds of ESOS audits were found to have non-conformances during ESOS phase 2 – with the majority linked to poor record keeping.

What is an ESOS evidence pack?

An ESOS (Energy Savings Opportunity Scheme) audit evidence pack is a comprehensive compilation of documentation and information gathered during the process of conducting an ESOS audit.

This pack serves as a critical component in demonstrating compliance with ESOS regulations. The evidence pack typically includes energy consumption data, energy efficiency assessments, reports on identified opportunities, supporting calculations, and any relevant documentation demonstrating the implementation of energy-saving measures. It serves as a transparent and organised record of the audit process, ensuring that businesses can substantiate their adherence to ESOS requirements and showcase their commitment to improving energy efficiency.

So, what are the key things that you need to document in the evidence pack?

Contact details

You must include contact details on the participating undertakings and the responsible undertaking (where a group of companies are participating under the highest parent company). Details are required for the responsible person for ESOS within the organisations – this could be the sustainability manager, environment, health & safety manager, finance director etc. – as well as details on the board directors or equivalents who have reviewed the ESOS report.

Corporate group structure

A corporate organogram should be included to show the group structure, showing all active, dormant and holding companies. This includes any overseas parents and sister organisations or groups which are owned by the same parent. The corporate structure should show turnover, balance sheet and employee number to indicate which company(s) meet the qualification threshold, and which SMEs qualify by proxy.

Letters of disaggregation

Where a corporate group decides to submit separate ESOS compliance for each of its entities, there should be documentation to demonstrate this. For each subsidiary company, there should be a letter between them and the parent company delegating the responsibility. This must be signed by a director (or equivalent) of each business.

Summary of business activities

For each participating organisation, there should be a brief description of the types of activity that the company undertakes, the number of sites it operates, the number of vehicles within the fleet, and whether or not employees conduct mileage in their own vehicles (grey fleet).

Reference period

The evidence pack should make clear which 12-month period has been used to determine the total energy consumption (TEC). The 12-month period must span the ESOS qualification date of 31 December 2022.

Changes during reference period

If any significant changes to the business operating model occurred during the reference, such as mergers, acquisitions, divestments etc. these should be documented.

List of energy consuming sites

Where a company has multiple sites, the evidence pack should document the address, nature of the operations and whether or not the company has direct billing, recharged based on specific consumption. If energy consumption is unknown, the company should work with its landlords to determine if energy use can be reasonably estimated, and which party takes responsibility for the energy in relation to ESOS compliance.

List of vehicles

If the business has a company-owned or managed vehicle fleet, an accurate list of vehicles should be maintained in the evidence pack with make, model, registration and other defining characteristics.

Mobile plant inventory

Similarly, an inventory of mobile plants should be kept which may include forklifts and excavators. The list is only to include owned assets or assets which are on long-term lease which were active on the 31 December 2022 and will also be active on the 5 June 2024.

Primary energy data

All supporting primary data should be stored in a comprehensive, organised and chronological fashion. This may include fuel card reports, electricity and gas invoices, employee mileage claims etc.

Estimation methodology

It is unlikely that an ESOS energy audit will have 100% data completeness. Typically, there may be a missing invoice here and there, or perhaps data may not be historically available for a newly acquired company. In such cases, the estimation of energy consumption is perfectly acceptable and can take many forms. The key is to document the estimation techniques and assumptions made to allow the scheme administrator to see your working.

Sampling approach

For companies with large estates, you will likely use a sample approach. There is no set way to determine an appropriate sample – it depends on several different factors, and it is open to interpretation. If you have 1,000 properties which are all largely identical, a 1% sample might be justifiable. If you have 10 sites that all do very different things, a 50% sample might be needed. A representative cross-section of your estate will be agreed upon with your Lead Assessor. The scheme administrator is looking for the logic behind this decision to be robust and written down.

Energy profiles

As part of any ESOS assessment, energy profiles help the organisation to understand how energy is being used in their business. An energy profile comes in many different forms – from analysing historical annual energy use to seasonal changes, heating and cooling degree days and half-hourly data. It also includes calculating key performance indicators such as kWh/m2 of floor area or kWh per unit produced.


Your ESOS audits should have a variety of different recommendations ranging from behavioural change, administrative enhanced controls, plant and equipment upgrades, product design, process efficiencies, renewable energy etc.

Payback periods and/or life cycle analysis

For most no or low-cost recommendations, a simple payback period of a year will be sufficient. However, for higher capital investment projects it is recommended that a full life cycle cost analysis is carried out. It is always beneficial to have at least one LCCA completed as part of any ESOS audit.

Prioritised action plan

A summary of all recommendations highlighted in your ESOS energy audits should be stored. It is expected that these are ranked based on such actors as ease of implementation, CAPEX, OPEX savings and payback periods.

Lead assessor sign-off

Once you’ve got all your evidence together, completed your audits and extrapolated the savings to the rest of the estate (if needed) – your Lead Assessor will review compliance against the ESOS regulations and sign off.

Board director sign-off

If you have had an external Lead Assessor sign off your compliance report, then you only need one board director to sign it. If your Lead Assessor is internal, you need two board directors’ signatures on your compliance report.

Maintaining your evidence pack

You must maintain your ESOS evidence pack for at least two subsequent ESOS phases. This means you need to keep those records safe and accessible for a minimum of eight years. There have been examples of companies misplacing ESOS data when key members of staff leave. To avoid this, make sure all your evidence pack is saved in a central secure location where multiple senior stakeholders have access.

Do you have questions about the latest ESOS phase 3 deadline or would like to book an ESOS Audit?

Speak to one of our ESOS Lead Assessors today

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