Energy Savings Opportunity Scheme

Improve energy efficiency and remain compliant with expert ESOS support.

esos

The Energy Savings Opportunity Scheme (ESOS) is a mandatory UK energy assessment scheme designed to help organisations identify opportunities to improve energy efficiency, reduce operational costs and support long-term sustainability goals.

Navigating the complexities of ESOS compliance can feel daunting. ESOS Phase 3 introduced additional requirements, including an ESOS Action Plan and annual progress updates. Our experts guide you through every step of the process, ensuring all required documentation is prepared accurately and submitted on time.

We help organisations achieve ESOS compliance while identifying opportunities to improve energy efficiency, reduce operational costs and support wider sustainability objectives.

Understand your obligations and stay compliant

Understanding who needs to comply with ESOS, what actions are required and how energy assessments support wider efficiency goals will help organisations maintain compliance, improve data accuracy and identify opportunities to reduce energy waste.

For the current reporting phase, 6 December 2023 to 5 December 2027 ESOS Phase 4, organisations are required to comply if either of the following applies:

  • employs 250 or more members of staff
  • annual turnover exceeds £44 million and annual balance sheet total exceeds £38 million

Understanding qualification requirements for ESOS compliance can be complex, particularly for organisations operating across multiple entities or sites. Our specialists help determine your obligations and ensure the correct route to compliance is followed.

To comply with ESOS, organisations must:

  • calculate total energy consumption
  • identify areas of significant energy consumption
  • complete the required audits for one year’s consumption under the direction of a lead assessor
  • submit an ESOS notification of compliance on the MESOS portal
  • maintain records of compliance within an evidence pack

Our experienced assessors support organisations through the entire ESOS compliance process, from energy data collection and auditing through to reporting and submission.

Following submission of the compliance notification, organisations must produce an action plan setting out:

  • what actions will be taken to reduce energy consumption
  • when improvements will be implemented
  • whether actions were identified through the ESOS assessment
  • expected energy savings over the four-year period covered by the action plan
  • how savings have been estimated

The introduction of action plans through ESOS Phase 3 has increased the focus on accountability and measurable progress against identified energy-saving opportunities.

Following submission of the action plan, organisations must submit annual progress updates against their commitments during the subsequent two years.

The deadlines for the third compliance period are:

  • 5 December 2025
  • 5 December 2026

Each update relates to the preceding 12-month reporting period and is intended to demonstrate progress made against planned energy-saving actions.

Annual progress update deadlines have currently only been confirmed for ESOS Phase 3. Guidance relating to any additional reporting obligations for ESOS Phase 4 is expected from the UK Government ahead of the 5 December 2027 compliance deadline.

These annual reporting obligations reinforce the importance of maintaining an ongoing and structured approach to ESOS compliance.

What are the benefits of ESOS?

ISO 50001 can be a route to ESOS compliance

ISO 50001 is a voluntary international standard that applies to organisations of any size and provides a framework for establishing, managing and improving energy consumption and efficiency.

Achieving ISO 50001 certification can support ESOS compliance by reducing the need for separate energy audits under certain circumstances.

We guide organisations through the certification process using a practical and achievable approach designed to support long-term improvement and compliance objectives.

Experienced energy assessors guide your route to compliance

We manage the entire data collection and reporting process through to compliance.

Our lead ESOS assessors compile data for the notification of compliance and oversee completion of the action plan and progress updates in line with the criteria and deadlines set by the Environment Agency.

This end-to-end support helps reduce the administrative burden associated with ESOS compliance while improving confidence in the quality and accuracy of submissions.

Avoid fines and safeguard your reputation

Penalties for failing to comply fully with ESOS, or for providing false or misleading statements, range from £5,000 to £90,000.

Penalised organisations may also be publicly named, creating potential reputational risk.

By taking a proactive approach to ESOS compliance, organisations can reduce risk, strengthen governance and demonstrate commitment to energy efficiency and sustainability.

ESOS Phase 4

Phase 4 places increased emphasis on accountability, energy data quality and demonstrating progress against identified energy-saving opportunities. As ESOS requirements continue to evolve, organisations may need stronger evidence gathering, clearer reporting processes and better alignment between ESOS compliance and wider sustainability objectives.

Our experts help organisations prepare for Phase 4 through energy assessments, compliance support and practical efficiency recommendations that support long-term operational improvement.

Learn more
esos
ESOS Lite: Choosing Zenergi for ESOS compliance

Organisations choose Zenergi because they need ESOS support that is practical, proportionate and easy to manage. Not every organisation needs a fully managed ESOS compliance service, but many still need expert guidance to understand their obligations, reduce administrative pressure and move forward with confidence.

That is why Zenergi offers ESOS Lite: a streamlined route for organisations that want targeted support with ESOS compliance without the scale or complexity of a full-service approach. ESOS Lite is designed to help you make sense of the requirements, prepare the right evidence, understand what action is needed and stay aligned with evolving regulatory expectations, including ESOS Phase 4.

With ESOS Lite, Zenergi gives you a clear, focused and flexible way to approach ESOS compliance, with the reassurance that deeper technical expertise is available whenever you need it.

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Our experts are here to help you manage your ESOS obligations with confidence.

Whether you need support understanding preparing action plans or managing annual progress updates, we provide reliable and compliant support tailored to your organisation.

Get in touch

Our experience

View all

Keeping energy costs under control for MK2 Real Estate

Discover how strategic procurement and ongoing oversight supports a growing property portfolio.

Mark Leonard

Strategic Client Partner

Zenergi

ESOS audit identifies £4 million in cost savings.

Explore how our ESOS Phase 3 audit uncovered a 5% energy reduction and a two-year ROI for a FTSE 250 food and drink manufacturer.

Energy reduction
33,093 MWh
Cost savings
£4.1 million
Carbon reduction
6,219
tCO2e

Annual saving of £61,000+ and immediate ROI from TM44 A/C Inspection.

Discover how a global data centre accessed major operational savings and maintained compliance.

Saving from cleaning the chillers
£
40,000+
Saving from adjusting the schedules
£
21,000+
Saving from upgrading the chillers
£
337,000+

Unlocking £5 million in savings with ESOS compliance

How a global renewable energy leader turned ESOS into a strategic opportunity for efficiency and sustainability.

Energy savings
26,000,000 kWh
Carbon reduction
8,300 tCO₂e
Cost savings
£4.91 million

Powering a historic dining hall for St John’s School.

Our Siteworks team streamlined a complex meter installation to meet ambitious timescales and ensure a new dining hall opened on time.

Karina Joshi

Strategic Customer Success Manager

St John's School Customer Success Manager

Bill Validation case study for independent school

How one conversation led to a £107,000 refund for a leading independent boarding school

Billy Pryke

Strategic Customer Success Manager

How our energy audit identified savings of £50,000 for E-ACT.

Discover how our exciting new programme for Multi-Academy Trust, E-ACT, identified huge carbon and cost savings in just six months.

Identified energy savings
246,193
kWh
Identified carbon savings
48.16
tCO2e
Identified cost savings
£
50,114

Greener transport: helping Gregory Group meet ambitious goals.

A science-led partnership with one of the UK’s largest transport groups that led to impressive net zero acceleration.

Harry Eaves

Senior Energy Consultant

Zenergi

Discover how our energy audits highlighted £94,955 of annual savings for Aldermore Bank.

We’re helping Aldermore Bank to reduce carbon emissions and cut costs – all while keeping the bank’s net zero strategy firmly on track.

Total carbon saving
172.6
tCO2e
Total annual cost saving
£
94,955

Leigh Academies Trust saves £500,000+ through flexible energy purchasing.

Discover how a 10+ year partnership helped one of the country’s largest and most established Multi-Academy Trusts navigate a turbulent energy market

Achieved savings: Year one
£
399,311
Forecast savings: Year two
£
200,287
Forecast savings: Year three
£
43,511

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FAQs

An ESOS assessment reviews energy consumption across buildings, transport and industrial processes. Organisations are required to calculate total energy use, identify significant energy consumption and complete energy audits under the direction of a lead assessor as part of ESOS compliance.

ESOS Phase 3 introduced additional requirements, including mandatory action plans and annual progress updates. These changes were designed to increase accountability and encourage organisations to take action on identified energy-saving opportunities.

ESOS Phase 4 is the current compliance period running from 6 December 2023 to 5 December 2027. The phase places increased emphasis on reporting quality, energy data accuracy and demonstrating progress against energy efficiency improvements.

Failure to meet ESOS compliance requirements can result in financial penalties ranging from £5,000 to £90,000, depending on the nature of the breach. Organisations that fail to comply may also be publicly named, creating potential reputational risk.

Yes. ISO 50001 can provide an alternative route to aspects of ESOS compliance by demonstrating a structured approach to energy management and continuous improvement.

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