ESOS legislation requires participants to:
1. Appoint a Lead Assessor
2. Measure your total energy consumption across your buildings, transport and industrial activities over a 12 month period (must include December 31st 2018).
3. Identify areas of significant consumption, accounting for at least 90% of your total consumption.
4. Conduct energy audits on areas of significant consumption and produce reports that identify cost-effective energy efficiency recommendations (based on life cycle cost analysis where possible).
5. Report compliance to the Environment Agency By 5 December 2023, You must ensure that your ESOS Assessment has been reviewed by a Board-level Director and approved by a Lead Assessor.
What is an ESOS Energy Audit
Participants can either undertake ESOS Energy Audits with the specific aim of complying with ESOS, or use previous energy audits to contribute to ESOS compliance provided that these meet the minimum requirements for ESOS Energy Audits. Energy audits are a valuable tool in understanding and improving the energy performance of your organisation. Undertaking energy audits allows you to:
• Measure and understand the energy consumption of your assets and activities.
• Build an energy consumption profile showing where and how your organisation consumes energy. This data can also be used to identify any variations in your energy use, both between areas and over time.
• Identify patterns, build explanations for these and identify any opportunities to reduce your overall energy use through increased levels of efficiency. Implementing such opportunities may provide long-term savings and reduce the impact of future energy price increases for your organisation. Improved efficiency can also boost productivity and growth.
There are different Audit Methods that can be implemented to conduct a ESOS Energy Audit. The Government has suggested several methods in their guidance:
ISO 50002 and BS EN 16247 Energy Audits set out a good practice method for identifying energy savings opportunities. It is for in-house managers or external consultants carrying out an energy audit, or as a guideline for organisations who want to understand what a good energy audit looks like.
The EN16247 series of standards also includes more detailed standards setting out possible auditing approaches to buildings, transport and industrial processes.
There are also more technical standards, such as ISO 14414: pump system energy assessment (see below). These may be suitable to deploy for particular aspects of a participant’s energy audits.
Individual auditors or energy auditing companies may also have their own in-house methodologies designed to meet the requirements of ESOS.
Other potentially relevant standards:
ISO 15099:2003 Thermal performance of windows, doors and shading devices — Detailed calculations. This standard specifies detailed calculation procedures for determining the thermal and optical transmission properties (e.g., thermal transmittance, total solar energy transmittance) of window and door systems. This standard may be applicable as an auditing methodology when seeking to determine the energy saving potential associated with an organisation upgrading the windows (inc. glazing) and/or doors in its buildings.
ISO 16346:2013 Energy performance of buildings — Assessment of overall energy performance. This standard defines the general procedures to assess the energy performance of buildings, including technical building systems. This standard may be an applicable auditing methodology for the assessment of energy saving potential from buildings.
ISO 15686-3:2002 Buildings and constructed assets, Service life planning, Part 3: Performance audits and reviews. The standard outlines the approach and procedures to be applied to planning, briefing, design, construction and, where required, the life care management and disposal of buildings and constructed assets. This standard may be applicable as an auditing methodology when seeking to determine the whole-life energy saving potential related to the replacement or retrofitting of a building and its likely performance over time.
ISO 11011:2013 Compressed air — Energy efficiency – Assessment. This standard sets out requirements for conducting and reporting the results of a compressed air system assessment from the energy input through the work performed by the compressed air system. This standard may be applicable as an auditing methodology when seeking to determine the energy saving potential associated with an upgrade/change to a compressed air system as part of an industrial process.
ISO/DIS 14414 – Pump system energy assessment. This Standard sets the requirements for conducting and reporting the results of a pumping system assessment. This standard may be applicable as an auditing methodology when seeking to determine the energy saving potential associated with an upgrade/change to a pump system as part of an industrial process.[/wr_item_tab][wr_item_tab heading=”Planning ESOS Energy Audit” disabled_el=”no” ]
An ESOS Energy Audit, or a number of audits, must cover all your areas of significant energy consumption. In planning how you will undertake your ESOS Energy Audits and compliance via other routes, you and/or your Lead Assessor should consider and make provisions for:
• identifying any work already undertaken in the compliance phase that may contribute towards compliance;
• agreeing on the audit methodology to be used, for example ISO 50002 or BS EN 16247.
• defining the scope of the audits to be undertaken (e.g. an audit of a defined organisation/ group member or a defined number of buildings, sites or transport assets);
• ensuring relevant staff are available to inform an audit and work with the Lead Assessor;
• agreeing an audit timetable, ensuring all audits will be completed suitably in advance of the compliance date; and
• agreeing a sampling approach – regarding the possible grouping of similar assets (e.g. similar retail units) for auditing and/or site visits:
ESOS Energy Audits must:
• Use 12 months of energy consumption data. For phase 3 compliance, this must include data recorded on the compliance date (31/12/2022).
• Produce cost-effective recommendations for the area being audited or confirm that there is no scope for cost-effective energy efficiency improvement.
• Be overseen, conducted or reviewed by an ESOS Lead Assessor
Each participant in ESOS is required to maintain an ESOS Evidence Pack detailing certain
aspects of their compliance with ESOS.
Ultimately, the responsibility for maintaining the Evidence Pack lies with the participant.
Your ESOS Evidence Pack should include:
• Details of the undertakings making up your participant and identification of the
• Details of the responsible board-level Director(s) or equivalents that have taken the lead
on signing-off your compliance with ESOS.
• Details of your Lead Assessor.
• The calculation of your total energy consumption.
• A list of your identified areas of significant energy consumption.
• Details of the routes to compliance used to cover each area of significant energy
• Your reasons, where applicable, for using less than 12 months of data for the
measurement of total energy consumption.
• Your reasons, where applicable, for using less than 12 months of data to support an
ESOS Energy Audit.
• Details of the audit methodology used in your ESOS Energy Audits.
• Your reasons, where applicable, for being unable to use verifiable data on energy use or
energy expenditure to support your calculation of total energy use and the methodology
of any estimation made.
• Justification, where applicable, where your auditor does not consider an energy
consumption profile in their audit of an area of significant energy use.
ESOS Energy Audits are required to include recommendations for cost-effective energy
efficiency improvements, where opportunities for such improvement exist. Recommendations
should directly save energy or lead to an indirect energy saving through improved energy
management (e.g. improved metering). Any recommendations must be for cost-effective
measures, where these exist.
ESOS Energy Audits may identify a number of types of cost-effective energy efficiency
An ESOS Energy Audit should:
• identify practicable energy saving opportunities for your organisation to implement;
• assess and report on the cost-effectiveness of each energy saving opportunity identified; and
• use appropriate calculations to determine potential savings in terms of potential energy and
Where practicable, an ESOS Energy Audit should:
• use life-cycle cost analysis (LCCA) instead of simple payback periods (SPP) for cost/benefit
analyses (see Section 184.108.40.206 for more details); and
• be informed by a minimum of 12 months of energy use data.
Energy saving opportunities and measures identified as part of an ESOS Energy Audit will need
to be reported to the participant. These opportunities/measures will then need to be presented
to a board-level director (or, in organisations without directors, a senior manager of equivalent
seniority) for sign-off (see Section 9.1). Directors will need to review a summary of all ESOS
recommendations and audits; they will also need to satisfy themselves that, to the best of their
knowledge, their organisation (and any organisations they are reporting on behalf of) have
complied with the scheme.
The regulations allows the participant and the Lead Assessor to agree a sampling approach – regarding the possible grouping of similar assets (e.g. similar retail units) for auditing and/or site visits.
The purpose of this is to reduce costs and work required. If a participant has 100 of small retail units located throughout the UK, your Lead Assessor is able to group units dependant on their building, energy consumption and HVAC system type allowing a representative sample to be audited. Therefore the costed energy efficiency recommendations are representative of properties in the group as a whole.