ESOS Phase 5: What the Delay of Mandatory Net Zero Requirements Means for UK Businesses

Understanding ESOS and Its Importance

The Energy Savings Opportunity Scheme (ESOS) is a mandatory energy assessment initiative established by the UK government to improve energy efficiency among large organisations. Under the scheme, businesses that meet specific employee, turnover, or balance sheet thresholds must undergo regular energy audits to identify potential cost and energy-saving measures.

ESOS operates in four-year compliance phases, with qualifying businesses required to complete audits and report their findings to the Environment Agency. With the scheme now confirmed to extend into Phase 5 (2027-2031), there are significant implications for organisations, particularly regarding the postponement of net zero requirements that were initially planned for Phase 4.

This article explores the key changes, what businesses need to know, and how energy professionals can capitalise on the opportunities ESOS Phase 5 presents.

ESOS Phase 4: Where Are We Now?

Currently, ESOS Phase 4 is in progress, with the qualification period running from 6th December 2023 to 31st December 2026. Any organisation that meets ESOS eligibility requirements within this timeframe must conduct an energy audit and submit their compliance notification before the deadline of 5th December 2027.

Who Qualifies for ESOS?

A business must comply with ESOS if, on the qualification date (31st December 2026 for Phase 4), it meets at least one of the following criteria:

• 250 or more employees
• Annual turnover exceeding £44 million and a balance sheet total of more than £38 million

Organisations that qualify are required to appoint an ESOS Lead Assessor, who will conduct audits and identify practical energy-saving opportunities. The goal is to help large businesses reduce energy waste, lower costs, and cut carbon emissions.

Why Has the Government Delayed Mandatory Net Zero Requirements?

One of the most significant planned ESOS Phase 4 changes was the introduction of mandatory net zero considerations within energy audits. Initially, this was intended to push businesses towards stronger decarbonisation efforts.

However, the government has now delayed this requirement until Phase 5 (2027-2031), citing the need to give businesses more time to prepare and to assess the impact of recent ESOS legislative updates.

Key Reasons for the Delay:

1. Delays in Phase 3 Legislation – Changes introduced in Phase 3 of ESOS (2019-2023) faced setbacks, impacting the planned timeline for Phase 4 updates.
2. Time for Businesses to Adapt – Introducing net zero requirements is a significant shift, and companies need sufficient time to adjust their energy strategies accordingly.
3. Governmental Review of ESOS’s Role – The Department for Energy Security and Net Zero (DESNZ) is taking additional time to evaluate ESOS within the broader energy and emissions reporting framework before enforcing stricter compliance measures.

While the net zero requirement delay gives businesses a temporary reprieve, it also signals that stricter sustainability regulations are coming in Phase 5. Companies should therefore proactively implement energy efficiency measures now to stay ahead of compliance obligations.

Changes to ESOS Qualification Thresholds Postponed

Alongside the delay of net zero requirements, the government has also decided not to align ESOS qualification thresholds with the Streamlined Energy and Carbon Reporting (SECR) scheme in Phase 4.

The proposal aimed to bring ESOS eligibility in line with SECR, but for now, the existing qualification criteria (250+ employees or financial thresholds) will remain unchanged.

Instead, any potential adjustments to qualification thresholds will be reviewed separately as part of broader business energy and emissions reporting reforms.

This means that companies currently outside of ESOS compliance requirements will not need to prepare for additional reporting obligations in Phase 4—though future changes remain possible.

What Businesses Should Do Now

Although net zero requirements have been delayed, companies should not wait until Phase 5 to take action. Proactively addressing energy efficiency and carbon reduction now can lead to:

• Lower operational costs through reduced energy consumption
• Improved sustainability credentials and corporate reputation
• Better compliance preparedness for future regulatory changes

Key Steps for Businesses:

1. Conduct an Early Energy Audit – Even if not required yet, a voluntary ESOS audit can identify immediate energy-saving opportunities.
2. Implement Energy Efficiency Measures – Upgrading lighting, improving insulation, and optimising HVAC systems can cut energy costs before regulations tighten.
3. Monitor and Report Energy Usage – Establishing robust energy data tracking will make future compliance easier and more efficient.
4. Engage an ESOS Lead Assessor Early – Securing expertise in advance can help businesses navigate compliance smoothly while maximising energy savings.

By taking these steps now, businesses can gain a competitive advantage and ensure they remain ahead of future ESOS regulatory shifts.

Conclusion

The extension of ESOS to Phase 5 (2027-2031) and the postponement of mandatory net zero requirements offer businesses an opportunity to prepare for stricter energy regulations.

While the immediate compliance burden has eased, organisations should act now to improve energy efficiency, reduce costs, and build resilience for future net zero commitments.

As the UK moves towards greater sustainability mandates, businesses that proactively engage in energy-saving measures will be best positioned to thrive in the evolving regulatory landscape.