ESOS Update on Action Plan Progress Reviews – July 2025 

As the UK continues to push forward with its Net Zero ambitions, the Energy Savings Opportunity Scheme (ESOS) remains a key regulatory mechanism for encouraging large organisations to identify and act on energy efficiency opportunities. Since its inception in 2014, ESOS has evolved significantly. From a compliance-driven reporting exercise to a more structured and accountable framework aimed at delivering real energy and cost savings. 

This update explores the latest developments in Phase 3 of the Scheme, including the introduction of mandatory action plan progress reviews and the launch of the new MESOS reporting platform. With the first progress update deadline approaching in December 2025, this article outlines what organisations need to know, what’s changed, and what’s coming next as we look to the current Phase 4. 

ESOS

When ESOS was introduced in 2014 many companies simply said it was an administrative waste of time and money. A report was done and submitted to the Environment Agency (EA) and then nothing would happen for four years until the next report was due with nothing required again until the next four-year cycle – and so it would go on. The idea of the requirement for the ESOS report to be signed off by the Board, was that as the report would contain financial savings opportunities. The management board would then simply implement the changes as ‘good business sense’.   

Phase 3

By Phase 3 of the Scheme it was clear that ESOS for many companies was managed as a job-to-do, not as a financial and energy saving review and opportunity.  So, within Phase 3 the change was introduced for:  

• the action plan to be submitted to the EA as part of the submission; and 
• for companies to complete 2 annual progress updates of the action plan, again to be submitted to the EA. 

For Phase 3, the EA have developed and implemented MESOS – the ‘Manage your Energy Savings Opportunity Scheme’ online reporting system. Companies with obligations under ESOS Phase 3 had a requirement to upload their action plan to the MESOS system by 5^th December 2024, subsequently extended to 5^th March 2025.  

The EA has confirmed that the functionality for the 1^st Progress Update has now gone live. The deadline for companies to submit their progress updates is 5^th December 2025.  The 2^nd update will be due by 5^th December 2026.   

Phase 4

In Phase 4, the government are introducing still tougher regulations to drive action – alongside the annual progress updates. There will be a requirement for companies to explain missed action plan commitments. The risk here of course is that action plan commitments get less ambitious so there is less risk of them being missed. But lead assessors still have an obligation in their report to identify savings opportunities, so we will see how this balances out over time.   

Some thought ESOS would be dropped with Brexit, as its genesis was based in EU Regulations. But this has not been the case. Effectively ESOS is another tool in the government’s kitbag to support its Net Zero ambitions, so it is being used to drive the transition. It is likely to get tougher rather than lighter as each Phase develops. 

If you need help with ESOS please do contact the team at E4environment.  We’re not Lead Assessors but we know some who are and can advise on how the system works.