Getting ahead of ESOS Phase 4: practical steps you can take now

The December 2027 deadline for ESOS Phase 4 might seem a while away, but there are actions you can take now to make compliance easier. At Concept, we’ve already started supporting clients with Phase 4, and we know organisations that begin early are more likely to unlock real value from the scheme by making meaningful progress on energy reduction. 

In this blog post, we explain what you can be doing now to make the most of compliance.  

1. Appoint a Lead Assessor

ESOS requires you to appoint an approved Lead Assessor to review your assessment and determine whether it meets the scheme’s requirements. 

In previous phases, there has been a bottleneck in the availability of Lead Assessors as the compliance deadline approaches. This could become even more challenging in Phase 4, as two alternative compliance routes (Display Energy Certificates and Green Deal Assessments) have been removed.  

Starting early will help you avoid capacity issues as demand for Lead Assessors grows, spread costs and resources over a longer period, plus ensure audits are thorough and genuinely useful. 

2. Understand your corporate structure

If you are part of a corporate group, you will need to establish which companies within the group are in scope of ESOS. If the group includes at least one UK “large undertaking”, the ESOS rules generally apply across the group’s UK operations. In most cases, the highest UK parent company is responsible for coordinating compliance, although groups with overseas parent companies or more complex structures may have different reporting arrangements. 

Because the rules can be complex, it’s important to establish exactly which legal entities are in scope and which company is responsible for compliance.  

3. Compile a list of sites and operations

Once you’ve identified which companies are in scope, compile a complete list of the sites and operations that need to be included in your ESOS assessment. ESOS covers energy used in buildings, transport and industrial processes, so it’s important to identify all relevant energy-consuming activities across your organization or group.  

4. Start gathering and cleaning data

We are already in the data collection period for ESOS.  

As with previous phases, Phase 4 requires 12 consecutive months of verifiable energy consumption data. This 12-month period must include the qualification date of 31 December 2026, meaning you could have started data gathering as early as 1 January 2026. 

Many organisations struggle with inaccurate or incomplete numbers, so you’re not alone if this is a hurdle to getting started. Concept can help you implement systems that improve data accuracy, streamline the process and make ongoing reporting easier.  

5. Complete your site visits

Your energy audit must include site visits to assess energy consumption across a representative sample of your buildings, transport and industrial processes. As we’re within the Phase 4 compliance window, you can start these now.  

Depending on the size and complexity of your organisation, the audit process can take significant time to complete. Starting site visits early allows you to gather better information, engage with on-site teams and identify opportunities without the pressure of an approaching deadline.  

6. Identify and prioritise opportunities

Early audits give you time to assess which recommendations are viable, build business cases and plan implementation, rather than simply reporting findings for compliance purposes. 

Phase 4 builds on previous phases but introduces a stronger focus on accountability and action. This shift began in Phase 3, but there is now even greater emphasis on developing action plans and reporting on implementation progress.  

The real value of ESOS is not just compliance. When approached properly, it can support better-informed investment decisions, reduce energy costs and help organisations make meaningful progress towards their wider sustainability goals. 

Advice and support

Concept Energy has been supporting clients with ESOS since the scheme began in 2014. As approved Lead Assessors with experience in a range of sectors, we understand both the compliance requirements and the practical realities of delivering meaningful energy improvements.  

Whether you’re ready to begin audits, improve your data, or simply want to understand what Phase 4 means for your organisation, we’re here to help. Get in touch with our team below.