Who Needs to Comply?
You must comply with ESOS Phase 3 if your business is classified as a large undertaking in the UK, meaning that on the qualification date (31 December 2024), your business either:
- Employs 250 or more people, or
- Has an annual turnover exceeding £44 million and a balance sheet over £38 million.
Importantly, if you’re part of a corporate group that meets these thresholds in aggregate, your organisation is still required to comply.
What’s Different in Phase 3?
The UK government has introduced significant changes in Phase 3 to improve the effectiveness of ESOS and ensure that it drives measurable energy savings:
1. Mandatory Energy Efficiency Action Plans
You now need to develop and submit a plan for how your organisation intends to implement the energy-saving opportunities identified in the audit.
2. Director-Level Sign-Off
A senior company director must now review and sign off on the audit and action plan, increasing accountability at board level.
3. Standardised Reporting Format
All reports must follow a standardised format set by the government, no more vague or generic assessments.
4. Public Reporting (Planned for Phase 4)
While not yet live, future phases will require you to publicly disclose energy performance data. Businesses that fail to act now risk being exposed later.
What Happens If You Miss the Deadline?
Non-compliance with ESOS is a serious offence.
The Environment Agency has stepped up enforcement. Fines and public penalties are already being issued for organisations that failed to comply in earlier phases.
If you miss the 5 December 2025 deadline, you could face:
- A fixed penalty of up to £50,000
- Daily fines of £500, for up to 80 days of non-compliance
- Ineligibility for public sector tenders and funding opportunities
- Reputational damage that could affect investor confidence and stakeholder trust
Worse still, many businesses wait until the final quarter to act, only to find no qualified assessors available, rushed audits or incomplete reports.
Why You Need to Start Now
Here’s the reality: compliance takes time.
Most energy audits, especially for large multi-site organisations require:
- Several weeks to gather and analyse consumption data
- Site visits, staff interviews, and process observations
- Detailed reporting, board sign-off, and official submission
Add to that the rising demand for ESOS Lead Assessors across the UK, and the risks of delaying become obvious.
By Q4 2025, many top-tier auditors will be fully booked and prices will rise. Leaving it late could mean non-compliance and fines.
How Celtic Dynamics Can Help
At Celtic Dynamics, we are trusted specialists in energy auditing and compliance across the UK and Ireland. We deliver end-to-end ESOS Phase 3 support, including:
- Free initial consultation to assess your obligations
- Qualified ESOS Lead Assessors with a strong track record
- Remote or in-person audits, depending on your needs
- Clear, actionable Energy Efficiency Action Plans
- Compliance documentation formatted to government standards
- Guidance on funding, grants, and implementation
We’ve worked with leading retailers, healthcare providers, logistics groups and manufacturing firms to turn compliance into savings.
