ESOS Phase 4 · regs 21 and 30
ESOS lead assessor and sign-off: who assesses, who signs
An ESOS Phase 4 assessment needs two kinds of person: a lead assessor who does or reviews the work, and a responsible officer who answers for it.
The number of responsible officers turns on a test of independence in regulation 30 that the guidance paraphrases loosely.
Approved registers
Seven registers, one competence standard
The GOV.UK approved register list names seven bodies; older lists that include IChemE or Stroma are out of date.
What qualifies an individual is a place on that body’s ESOS register, not membership of the body.
The competence standard is PAS 51215:2014, still named in regulation 12 for Phase 4.
The lead assessor must be on a register at the time of the energy assessment, and checking that is the participant’s responsibility.
New in Phase 4
A duty on the assessor, not the company
SI 2026/701 inserted regulation 21(2A), which puts a personal duty on the lead assessor.
Within seven days of completing an ESOS assessment, the lead assessor notifies their approval body.
The notice gives contact details for at least two people at the responsible undertaking, one of them the responsible officer.
The register body now hears directly that an assessment exists, so a notification to the Environment Agency that does not match will be visible.
Sign-off
One responsible officer or two
One responsible officer confirms the assessment.
Two responsible officers confirm: a non-independent assessor, or no lead assessor at all.
Source: SI 2014/1643 reg 30(3), (3A), (4).
The guidance calls the two cases external and internal; the Regulations say independent and not independent, and the difference matters.
A consultant is not independent if, in the last twelve months, they were an employee, director, partner, manager or shareholder of the participant, or married to or in a civil partnership with one.
A responsible officer is a director within the Companies Act or a person with management control; “board level” is not in the Regulations.
When no assessor is needed
Three cases with no lead assessor
Each case removes the lead assessor, but none removes the notification of compliance.
ISO 50001 does not excuse the ESOS assessment itself under regulation 20; it stands in for the assessor, audit and report duties.
For the action plan that follows sign-off, see action plans and progress updates, and the family’s ESOS Phase 4 compliance guide on uksrs.org.uk.
| Case | Effect | Sign-off |
|---|---|---|
| Total consumption below 40,000 kWh | No lead assessor duty | Two officers |
| Zero consumption | Assessment deemed complied with; still notify | Two officers |
| ISO 50001 covers total or significant consumption | Assessor, audit and report duties deemed met | Per reg 30 |
Frequently asked
Questions people ask
Do I need an ESOS lead assessor for Phase 4?
Yes, unless total energy consumption is below 40,000 kWh, the participant’s consumption is zero, or ISO 50001 certification covers total or significant consumption.
The lead assessor must be on one of the approved registers at the time of the assessment.
How many ESOS lead assessor registers are there?
Seven, on the GOV.UK list last updated 16 February 2026: the Association of Energy Engineers, CIBSE, Elmhurst Energy Systems, the Energy Institute, the Energy Managers Association, the Institute of Sustainability and Environmental Professionals, and Quidos.
Membership of a body is not the same as being on its ESOS register.
What is the lead assessor’s new duty in Phase 4?
SI 2026/701 requires the lead assessor personally to notify their approval body within seven days of completing an ESOS assessment, with contact details for at least two people at the responsible undertaking, including the responsible officer.
Who signs off an ESOS assessment?
Responsible officers: a director, or a person exercising management control.
One is enough where the lead assessor is independent of the participant; two are needed in every other case, including where no lead assessor was appointed.
Is an external consultant always independent for ESOS?
No. Under regulation 30(4) a lead assessor is not independent if, in the last 12 months, they were an employee, director, partner, manager or shareholder of the participant, or the spouse or civil partner of one.
An external consultant who is a shareholder needs two responsible officers, whatever the guidance’s external and internal labels suggest.
What competence standard applies to ESOS lead assessors?
PAS 51215:2014, which regulation 12 still names and the GOV.UK hub confirms remains the competence standard for Phase 4.
The 2025 parts of PAS 51215 may be used voluntarily for net zero considerations.
Sources
Primary sources
Every figure, date and status on this page traces to the instrument’s owner.
Secondary commentary is never the source for a number.
- legislation.gov.ukThe Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643)
The scheme itself. The consolidated text does not yet show the 2026 amendments.
- legislation.gov.ukSI 2014/1643 regulation 12 — approved registers and the competence standard
Fixes PAS 51215:2014 as the lead assessor competence standard.
- legislation.gov.ukThe Energy Savings Opportunity Scheme (Amendment) Regulations 2026 (SI 2026/701), in force 22 July 2026
Every Phase 4 change: routes, savings reporting, the action plan review, the third progress update.
- legislation.gov.ukSI 2026/701 — Explanatory Note
The government’s own summary of what the 2026 amendments do.
- legislation.gov.ukThe Energy Savings Opportunity Scheme (Amendment) Regulations 2023 (SI 2023/1182)
Raised the significant-consumption floor from 90% to 95% and added the 40,000 kWh limb.
- legislation.gov.ukSI 2014/1643 regulation 33A — zero energy consumption
Inserted by SI 2026/701: deemed compliance, but a notification is still made.
- Environment Agency / GOV.UKEnergy savings opportunity scheme (ESOS): find out if you qualify and how to comply (updated 2 September 2026)
The GOV.UK hub, now a Phase 4 page, and the approved lead assessor register list.
- BSIPAS 51215 — Energy efficiency assessment: competence of a lead energy assessor
The 2014 edition remains the ESOS competence standard under regulation 12.
- Environment AgencyHow to comply with the Energy Savings Opportunity Scheme (ESOS) phase 4 (30 July 2026)
The regulator’s guidance; a restatement of the Regulations, never the master.
- Environment AgencyComply with the Energy Savings Opportunity Scheme (ESOS) phase 4 — publication page
Published 30 July 2026.
- legislation.gov.ukSI 2014/1643 regulation 30 — responsible officers and independence
One responsible officer where the lead assessor is independent; two in every other case.
- legislation.gov.ukSI 2014/1643 regulation 21 — the lead assessor
The duty to appoint, and the 40,000 kWh limb at reg 21(3).