What is ESOS ?

The Energy Savings Opportunity Scheme (ESOS) is a mandatory energy assessment and energy-saving identification scheme established under the UK’s implementation of the EU Energy Efficiency Directive. It is governed by the Energy Savings Opportunity Scheme Regulations 2014, overseen by the Environment Agency (and equivalents in Scotland, Wales and Northern Ireland). The scheme requires qualifying organisations to measure their total energy consumption across buildings, industrial processes, and transport, carry out energy audits to identify cost-effective savings opportunities, and report compliance every four years.

ESOS applies to all UK organisations defined as a “large undertaking”, meaning any company (or part of a corporate group) with 250 or more employees, or an annual turnover exceeding £44 million and an annual balance sheet total over £38 million. Compliance involves calculating total energy use, auditing at least 95% of that consumption, identifying efficiency opportunities, and submitting an ESOS report signed off by a board director and an ESOS Lead Assessor. Organisations that fail to comply can face substantial civil penalties, including fines of up to £50,000 plus daily penalties for continued non-compliance, as well as potential reputational damage.

ESOS was introduced in 2014 (Phase 1), with subsequent phases every four years — Phase 2 compliance was due by 5 December 2019 and Phase 3 by 5 June 2024. Phase 4, due by 5 December 2027, will incorporate new requirements following the UK’s post-Brexit review of the scheme, including mandatory reporting on actions taken since the previous phase and more detailed data submission. Over time, ESOS is expected to integrate more closely with wider UK net zero and energy-efficiency policy, driving deeper decarbonisation and improved energy performance across large organisations.

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How can we help?

What’s the Payback can significantly simplify and accelerate ESOS compliance through our unique software platform, which automates much of the data gathering, analysis, and reporting process, delivering rapid energy assessments and actionable recommendations at a fraction of the usual time and cost. Our technology links directly to real-world energy-saving solutions and supplier data, instantly calculating potential savings and payback periods while ensuring full regulatory compliance. Combined with our nationwide network of highly qualified, experienced ESOS Lead Assessors, we offer organisations a seamless, cost-effective route to meeting their legal obligations and unlocking meaningful energy and carbon reductions.

Received an Enforcement Notification?

If your organisation has received an ESOS compliance enforcement notice, it’s vital to act quickly. The Environment Agency sets strict deadlines for addressing non-compliance, and delays can lead to escalating fines and reputational risk. Our team can step in immediately to assess your situation, review any existing work, and outline the fastest route to achieving compliance — ensuring you meet regulatory requirements and minimise potential penalties.

With our powerful software tools and nationwide network of experienced ESOS Lead Assessors, we can rapidly collect and analyse your energy data, complete the required audits, and prepare the documentation needed for submission. By streamlining the entire process, we help you respond to enforcement action quickly, efficiently, and with confidence — turning a compliance risk into an opportunity to improve energy performance and cut costs.