ESOS Phase 4: Why Early Action Beats Late Compliance

Guest blog by Duncan Wigney | SRD Technical Director and ESOS Lead Assessor

The Energy Savings Opportunity Scheme (ESOS) is entering its fourth phase. On the surface, the requirements look familiar: assess your energy use, identify opportunities to improve, and submit your report by December 2027. But in practice, Phase 4 is different.

This phase is not just about meeting a deadline. It’s about making progress. Businesses that approach it strategically will reduce costs, strengthen compliance, and position themselves for long-term carbon reduction.

What’s Changing in ESOS Phase 4?

While the core audit requirements remain in place, Phase 4 introduces new expectations. These include:

• More robust enforcement from the Environment Agency
• A stronger emphasis on how and when energy-saving opportunities will be implemented under the new annual ESOS Action Plan process that was introduced in Phase 3
• Closer alignment with Net Zero planning, Scope 1–3 reporting, and ESG disclosure

The scheme still requires organisations to calculate total energy consumption, audit at least 95% of it, and submit a report signed off by an accredited ESOS Lead Assessor. But the expectation now is that these reports will lead to measurable action, not just sit in a folder.

Why Waiting Comes at a Cost

Many businesses delay their ESOS preparation until the final year. This increases the risk of non-compliance but also limits the value of the process itself. Delaying can lead to:

ESOS Lead Assessor shortages. Lead Assessors are already in high demand. The later you start, the harder it is to secure someone with sector-relevant experience.

Data gaps. Gathering 12 months of usable, accurate data takes time, especially if sites use different systems or lack sub-metering.

Missed alignment with budget cycles. Many recommendations from ESOS require investment. If your report is finalised after internal capital budgets are set, those projects will be delayed another year.

Wasted savings. Every month you wait is a month of unnecessary energy spent. Some businesses identified savings of 10–15% during Phase 3 but had no time to act before submission.

Use ESOS to Drive Strategy, Not Just Compliance

Phase 4 creates an opportunity to go beyond minimum requirements. Here’s how businesses are turning ESOS into a strategic tool:

1. Align With Your CapEx Planning Cycles

The qualification date for ESOS Phase 4 is 31st December 2026, which means this date must fall within your chosen 12-month data period. While you won’t be able to start your data calculations until January 2027, site audits and preparatory work can begin at any time.

Starting early not only avoids a last-minute rush but also gives you the opportunity to allocate costs into your 2026/27 budget, helping to spread the investment and manage resources more effectively.

This approach makes it easier to secure funding for ESOS recommendations within your standard budget cycle.

2. Audit More Than the Minimum

The legal requirement is to audit 95% of your consumption. But many organisations choose to assess 100%, especially across multi-site portfolios. This gives a complete picture of energy usage and prevents any gaps that might later raise questions.

Even “low-consumption” sites can hold untapped savings, particularly in sectors like food processing, logistics, or manufacturing where usage patterns vary significantly.

3. Use the Audit to Improve Metering and Monitoring

ESOS often highlights a lack of visibility across sites. Poor metering makes audits more difficult, but more importantly, it prevents organisations from tracking and sustaining improvements.

Clients like Swire and APS used their audits to justify investment in circuit-level monitoring through Tritility’s Energy Metrics platform. This gave them continuous insight into consumption patterns, flagged anomalies, and made it easier to act on the audit’s recommendations, not just report on them.

If your audit reveals poor visibility, use it to drive the case for better measurement tools.

4. Pre-Qualify for Funding and Finance

Some businesses use their ESOS reports to support applications for external funding or green finance. Public grants such as the Industrial Energy Transformation Fund (IETF) or local authority schemes often require recent audit data and clear project proposals.

Completing your audit early gives you the option to apply, rather than being locked out by timing.

5. Support Broader Reporting Obligations

If your business reports under frameworks like SECR, TCFD, or publishes an ESG strategy, your ESOS findings can feed directly into Scope 1 and 2 disclosures, and in some cases, inform Scope 3 calculations where electricity use overlaps with supply chain emissions.

This increases the internal value of the report, making it useful to finance, procurement, and sustainability teams, not just compliance managers.

What We Learned From ESOS Phase 3

In Phase 3, we supported a wide range of clients across energy-intensive sectors. Common issues included:

• Incomplete site lists due to mergers, divestments, or reporting gaps
• Inconsistent transport data, especially from grey fleet usage
• Duplicate submissions across group structures with unclear responsibilities Rushed delivery, leading to missed insights and delayed investment

These are avoidable, but only if the process starts early and is guided by experienced support.

Choosing the Right Lead Assessor

Your ESOS Lead Assessor must be accredited, but they should also be a good fit for your business. Look for someone who:

• Understands your operational and sector-specific challenges
• Offers practical advice, not just technical reporting
• Can engage with your internal teams on realistic next steps
• Has the capacity to support you well ahead of the 2027 deadline

Tritility works alongside trusted ESOS Lead Assessors who take this partnership approach. We help manage the full process, from identifying your site list and validating data, to coordinating assessments and advising on follow-up actions.

Start Now to Feel the Benefit

You are not required to wait until the 2026 qualifying date to begin your ESOS Phase 4 process. In fact, every step you take now reduces risk, spreads workload, and opens the door to early savings.

To get started:

• Confirm your qualification status and site list
• Begin collecting energy data across buildings, transport, and processes Engage with a Lead Assessor early
• Use the audit timeline to support budget planning, Net Zero targets, or equipment upgrades

Need Help With ESOS Phase 4?

We support businesses across manufacturing, logistics, education, and other high consumption sectors. Our team can help you avoid the common pitfalls and make the most of the ESOS opportunity, not just to comply, but to improve.

Speak to us today about getting your ESOS Phase 4 strategy underway.