What ESOS consultants do
ESOS consultants deliver a complete ESOS consultancy audit: qualification check, energy audits, and the notification to the Environment Agency.
The Energy Savings Opportunity Scheme1 requires large UK undertakings to audit total energy consumption — buildings, transport and industrial processes — and identify cost-effective savings.
The assessment must be signed off by an approved ESOS lead assessor, which is why most organisations use specialist ESOS consultants.
Who qualifies for ESOS
A UK undertaking qualifies for ESOS as a “large undertaking” if it employs 250 or more people, or exceeds both the turnover and balance-sheet thresholds2.
| Test | Qualifies if |
|---|---|
| Employees | 250 or more |
| Turnover | More than €50m (≈ £44m), with balance sheet test |
| Balance sheet | More than €43m (≈ £38m), with turnover test |
Qualifying organisations comply through ESOS energy audits or certified ISO 500012 covering their full energy use — and must notify the Environment Agency either way.
The Phase 4 deadline
ESOS runs in four-year phases.
Phase 4 is the current cycle, and the dates are fixed.
| Milestone | Date |
|---|---|
| Phase 4 period | 6 Dec 2023 – 5 Dec 2027 |
| Qualification date | 31 December 2026 |
| Compliance notification deadline | 5 December 2027 |
Choosing ESOS consultants
Look for ESOS consultants with access to an approved lead assessor, experience across your asset types, and a method that reuses your energy data for other regimes.
The energy figures behind ESOS overlap heavily with SECR and feed the emissions inventory our carbon consultancy maintains — so a joined-up engagement avoids duplicated measurement.
How we help
As your ESOS consultants, Carbon Legal confirms qualification, runs the ESOS consultancy audit, arranges lead-assessor sign-off, and submits the notification.
Our ESOS consultants follow the full Phase 4 requirements detailed on our ESOS Phase 4 reference page.
Carbon Legal's ESOS consultants are specialists in ESOS consultancy audit services, not legal advisors.
We launch in Q3 2026 and are booking readiness reviews now.
Frequently asked questions
What do ESOS consultants do?
ESOS consultants assess whether your organisation qualifies, carry out the ESOS consultancy audit that covers total energy consumption across buildings, transport and industrial processes, and submit the compliance notification to the Environment Agency. The assessment must be signed off by an approved ESOS lead assessor.
What is the difference between ESOS consultants and an ESOS consultancy?
An ESOS consultancy is the firm; ESOS consultants — often qualified lead assessors — perform and sign off the audit. The deliverable is the same: a compliant ESOS consultancy audit and a notification submitted to the Environment Agency before the deadline.
When is the ESOS Phase 4 deadline?
The ESOS Phase 4 qualification date is 31 December 2026 and the compliance notification deadline is 5 December 2027. The four-year Phase 4 compliance period runs from 6 December 2023 to 5 December 2027.
Who qualifies for ESOS?
A UK undertaking qualifies if it employs 250 or more people, or has an annual turnover above €50m (≈£44m) and a balance sheet total above €43m (≈£38m). Qualifying organisations must complete ESOS energy audits or maintain certified ISO 50001 covering their energy use, and notify the Environment Agency.
Do we still need ESOS consultants if we have ISO 50001?
Organisations with ISO 50001 certification covering their entire energy use can use it to comply without separate ESOS audits, but they still need to notify the Environment Agency. ESOS consultants confirm whether your ISO 50001 scope is sufficient for the ESOS consultancy audit requirements.