With ESOS Phase 4 on the horizon, many organisations are asking the same question: “Do we really need to think about this yet?” Our answer is a clear yes!
ESOS Phase 4 raises the bar on how organisations demonstrate action, accountability, and progress on energy efficiency. We’re already working with businesses on Phase 4 because the decisions made today around data capture, governance, and assessor engagement will directly determine how smooth (or stressful!) this compliance process can be later.
When to Appoint Your ESOS Lead Assessor
One of the most common mistakes organisations make with ESOS is waiting too long to appoint their Lead Assessor. While Phase 4 deadlines fall in 2027, the reality is that effective compliance depends on work carried out well before then.
An ESOS Lead Assessor plays a critical role: they oversee the assessment methodology, review energy data, guide site selection for audits, and ultimately sign off that the submission meets regulatory requirements. Early appointment doesn’t change the core ESOS requirements but it does make the whole process significantly easier to manage.
- Planned data collection: Having a Lead Assessor in place early allows organisations to plan how data will be gathered and monitored throughout 2026, rather than trying to collate everything retrospectively. This spreads the workload, reduces last-minute pressure, and fits data collection more naturally around day-to-day business activity.
- Flexible scheduling: Signing up early provides far more choice when scheduling site visits and assessments. These can be planned at convenient times in 2026, avoiding clashes with operational peaks, shutdowns, or other business priorities, rather than having to fit everything into a narrow window close to the compliance deadline.
- Securing Lead Assessor availability: Demand for qualified ESOS Lead Assessors typically increases as deadlines approach. Appointing early helps organisations secure assessor availability well in advance, reducing the risk of delays caused by limited capacity later in the phase, which could otherwise put compliance timelines under pressure.
- Cost and budget certainty: Early appointment allows organisations to secure today’s pricing, avoiding potential inflationary increases or premium costs associated with urgent, last-minute appointments closer to the deadline. It can also enable costs to be spread across two financial years, providing greater flexibility within annual budgets.
- Smoother process: Perhaps most importantly, starting early allows the ESOS process to be delivered at a steady, manageable pace. Work is spread over a longer period, reducing pressure on internal teams and allowing ESOS to sit alongside other priorities rather than competing with them.
In short, early appointment gives organisations greater control over timing, cost, and workload throughout the next ESOS phase.
Book Your ESOS Auditor Early to Stay Ahead of the Deadline
One consistent lesson from previous ESOS phases is that demand for auditors rises sharply as the deadline approaches.
For ESOS Phase 4, the timing of assessment activity depends on both an organisation’s energy profile and the compliance route being used.
Where organisations are following the ESOS energy audit route for buildings, site visits are required to assess building energy performance. In these cases, building energy surveys can be completed during the 2026 calendar year, based on the agreed site sample, making 2026 the optimal window for carrying out these assessments.
However, not all ESOS routes involve site visits. Organisations using alternative compliance routes, such as ISO 50001 certification, are not generally required to undertake building surveys as part of ESOS. In these cases, early activity is typically focused on confirming scope, evidence requirements, governance arrangements, and how certification will be used to demonstrate compliance.
Similarly, where transport represents the majority of energy consumption, the transport assessment cannot be completed until a full calendar year of 2026 data is available. As a result, much of this work will naturally fall into 2027, regardless of when a Lead Assessor is appointed.
Even where assessment activity cannot begin immediately, agreeing the approach early provides clarity on timing, responsibilities, and deliverables, helping organisations plan realistically for the later stages of the phase.
It is also worth noting that ESOS Phase 3 Action Plan updates continue alongside Phase 4 and feed directly into the Phase 4 submission. This overlap makes forward planning particularly important for organisations with outstanding actions to explain, update, or complete.
Key Dates to Keep in Mind
While the exact timing of activity will vary by organisation, the following milestones apply across ESOS Phase 4:
- 2026: Energy consumption data must be captured across the full calendar year.
- 2026: Ideal window for completing ESOS building energy surveys.
- 5 December 2026: Deadline for the Phase 3 Action Plan Update.
- 31 December 2026: Qualification date for ESOS Phase 4.
- 2027: ESOS Phase 4 portal opens and submissions begin.
- 5 December 2027: Final compliance deadline.
Understanding these dates early helps ensure ESOS activities are scheduled appropriately and integrated alongside other business priorities.
Preparing Now for a Smoother ESOS Phase 4
ESOS is most effective when treated as an ongoing process rather than a one-off compliance exercise. Early clarity on data capture, portal access, governance responsibilities, and the chosen compliance route helps keep delivery proportionate and well-managed.
Overall, this provides organisations with the time and flexibility needed to meet ESOS requirements confidently, without unnecessary pressure as the deadline approaches.