ESOS: a route
Certification covering total or significant consumption deems the lead assessor, audit and report met.
Notification is still required.Energy · ISO standards
ISO 50001
ISO 50001:2018 is ISO’s standard for an energy management system: a policy, an energy review, indicators, baselines and continual improvement.
No UK law requires it, and it sets no level of saving.
Certification that covers total or significant energy use is an ESOS Phase 4 route, deeming three duties met, though never the notification.
The standard
What is ISO 50001?
A management system for energy, built on plan-do-check-act, that requires improvement without setting a level.
| Clause | What it is called | What it means in practice |
|---|---|---|
| 6.3 | Energy review | Where energy goes, and which uses are significant energy uses |
| 6.4 | Energy performance indicators | The measures used to show improvement |
| 6.5 | Energy baseline | The reference the indicators are compared against |
| 6.6 | Planning for collection of energy data | What is measured, how and how often |
| 9.1.2 | Evaluation of compliance with legal and other requirements | Checking the organisation meets its own energy obligations |
| 9.2 and 9.3 | Internal audit and management review | How the system checks and corrects itself |
The scope says it “requires demonstration of continual energy performance improvement, but does not define levels of energy performance improvement to be achieved” (ISO 50001:2018).
The 2024 amendment adds two sentences: clause 4.1 now asks whether climate change is a relevant issue, and clause 4.2 notes that interested parties can have climate-related requirements (IAF and ISO).
ISO 14001 moved to a 2026 edition; ISO 50001 did not, and an amended standard is still ISO 50001:2018 (ISO).
Status
Is ISO 50001 mandatory in the UK?
No. Three UK regimes accept or recommend it, and none requires it.
For an ESOS participant it is a choice between the ISO 50001 route and an ESOS energy audit; Display Energy Certificates and Green Deal Assessments are no longer routes (SI 2026/701).
Being in a Climate Change Agreement or the UK ETS does not count as ESOS compliance (EA guidance).
The permits guidance still refers to the 2010 permitting regulations, since replaced; only its ISO 50001 sentence is relied on here (EA and Defra).
How UK regimes treat ISO 50001
Permits: one option
“An energy management system like ISO 50001” or the BREF techniques.
Either meets the basic measure.CCAs: recommended
The government decided in October 2024 an EMS “will not be mandatory” for the new scheme.
But recommends one.ESOS Phase 4
How does ISO 50001 work for ESOS Phase 4?
Cover total or significant consumption with a valid, accredited certificate and three duties are deemed met.
Identifying significant consumption is elective: a participant that does not elect must cover its total consumption (reg 25(1)).
Partial certification counts only for the part it covers; the rest needs an ESOS audit and a lead assessor.
“ISO 50001 must cover 100% of your energy” was the Phase 3 rule and no longer applies.
The ISO 50001 route against an ESOS audit, side by side, is on ISO 50001 vs ESOS, and the whole phase on the ESOS Phase 4 guide.
The ESOS routeExplore
The ESOS route
Cover
Total consumption, or significant consumption of not less than 95%, measured in energy units or by spend.
The ESOS route
Certificate
Issued on or after 6 December 2023 and valid on 5 December 2027.
The ESOS route
Who certifies
A body accredited by UKAS, an EU national accreditation body or an IAF member.
The ESOS route
Never met
The notification of compliance, and the regulation 20 assessment duty.
One manufacturer
What does this look like for one manufacturer?
A manufacturer whose certified system covers 96% of its energy spend skips the audit but still has to notify.
It is an illustration, not a real company.
At 90% cover it would be deemed compliant only for that 90%, and would need an audit and a lead assessor for the rest.
With a certificate issued before 6 December 2023, it would need a new one, or an audit, for Phase 4.
- 1
Cover
Its certified system covers 96% of its energy spend, so it elects to identify significant consumption, which must be not less than 95% (SI 2014/1643 reg 25).
- 2
Certificate
Issued in 2024 and valid until 2028, so it falls in the Phase 4 window (EA guidance).
- 3
What is deemed met
The lead assessor, the ESOS audit and the ESOS report (SI 2026/701).
- 4
The other 4%
Can be treated as de minimis, chosen by the company (EA guidance).
- 5
Still to do
Director sign-off and the notification of compliance by 5 December 2027 (EA guidance).
What certification gives
What does ISO 50001 certification give you, and what not?
Three ESOS duties and a permit option; never the ESOS notification, never a performance level.
| Question | Answer | Source |
|---|---|---|
| Does it meet ESOS’s audit, lead-assessor and report duties? | Yes, where it covers total or significant consumption | SI 2026/701 |
| Does it meet the ESOS notification? | No: every participant notifies by 5 December 2027 | EA guidance |
| Does it meet a permit’s basic energy measure? | Yes, as one of two ways; the BREF techniques are the other | EA and Defra |
| Is it required for a Climate Change Agreement? | No, by the October 2024 decision; it is recommended | DESNZ |
| Does it prove a level of energy performance? | No: it requires improvement without defining how much | ISO |
Certification
How does ISO 50001 certification work?
A certification body audits the system to ISO 50003; UKAS accredits the body, and ISO certifies no one.
UKAS lists “Energy Management Systems Certification (EnMS) to ISO 50001”, with ISO 50003:2021 as the requirements for the certifying body (UKAS).
To check a certificate, find the issuing body in the UKAS directory with an energy management scope, then look the certificate up in UKAS CertCheck.
UKAS accredits bodies, never consultants, so a consultant can prepare you for certification but cannot certify you; more on UKAS accreditation.
- Year 1
Initial audit, in two stages
The body reviews the system, then audits it in operation. - Years 2 and 3
Surveillance audits
At least once a year. - Year 3
Recertification
A full audit before the certificate is renewed.
Your certificate
Does your certificate cover ESOS Phase 4?
Enter the cover, the dates, the edition and the body: the route, and what is left, follow.
Cover can be measured in energy units or by energy spend.
Whether you qualify for ESOS at all is a separate test, set by your size on the qualification date.
The answer is provisional; group structures and partial certificates need a closer look.
ISO 50001 · does it cover ESOS Phase 4?
Fill in all five to test the route.
Rules: SI 2014/1643 regs 25 and 33 as amended by SI 2026/701; Environment Agency, How to comply with ESOS phase 4. Whether you qualify for ESOS at all is a separate test.
A provisional reading, not advice on your group. Nothing you enter leaves your browser.
What is changing
What is changing for ISO 50001?
The standard is stable; its certification standard is under review, and ESOS Phase 5 dates are set.
Under systematic review is not the same as being revised: ISO has recorded neither a revision nor a confirmation for ISO 50003.
A certificate for the next phase must be valid on that phase’s compliance date.
What moves nextExplore
What moves next
ESOS Phase 5
Qualification date 31 December 2030; compliance date 5 December 2031.
Order of work
What should an organisation do first?
Decide what the system must cover, then the certification, then the ESOS paperwork that certification does not replace.
The ESOS rules, step by step, are on the ESOS Phase 4 guide.
An organisation running ISO 14001 as well can align the two systems; see ISO 14001.
- 1
Map energy use
By energy units or spend, to see what 95% would take.
- 2
Set the system’s scope
Total, or the significant uses you elect to identify.
- 3
Choose an accredited body
UKAS, an EU national accreditation body or an IAF member.
- 4
Time the certificate
Valid on 5 December 2027 for Phase 4.
- 5
Notify compliance
With director sign-off, by 5 December 2027.
ISO 50001 is a system for improving energy use, and for an ESOS participant it can replace the audit but never the notification.
- ISO 50001:2018
The 2018 edition is current, with one climate amendment
There is no ISO 50001:2024. - No level set
ISO 50001 requires continual improvement, not a target
The organisation sets its own. - Not less than 95%
Certification covering significant consumption deems three ESOS duties met
Notification is still due. - 5 December 2027
The certificate must be valid on the Phase 4 compliance date
And issued on or after 6 December 2023. - No UK law
Nothing in UK law requires ISO 50001
Permits and CCAs accept or recommend it.
How does ISO 50001 relate to ISO 14001?
Two management-system standards with the same structure; one for energy, one for the environment, on different editions.
Both received the same two climate sentences in 2024; only ISO 14001 has since moved to a new edition.
Neither is required by UK law.
Frequently asked
What else do people ask about ISO 50001?
What is ISO 50001?
ISO 50001:2018 is ISO’s standard for an energy management system.
It asks an organisation to set an energy policy, carry out an energy review, identify its significant energy uses, set energy performance indicators and baselines, and show continual improvement in energy performance. It does not set a level of improvement to reach.
Is ISO 50001 mandatory in the UK?
No. No UK law requires it.
It is one way to meet ESOS Phase 4, the Environment Agency accepts it as one way to meet a permit’s basic energy efficiency measures, and the government decided in October 2024 not to make an energy management system mandatory for the new Climate Change Agreements scheme.
Does ISO 50001 exempt you from ESOS?
Not entirely.
Where certification covers total or significant energy consumption (not less than 95%), the duties to appoint a lead assessor, carry out an ESOS audit and produce an ESOS report are deemed met.
The duty to notify compliance by 5 December 2027 still applies, and so does the ESOS assessment duty in regulation 20.
Is there an ISO 50001:2024?
No. ISO 50001:2018 was confirmed in 2024 and given a one-page climate action amendment on 23 February 2024.
An amended standard is still ISO 50001:2018.
How is ISO 50001 certified?
A certification body audits the energy management system under ISO/IEC 17021-1 and ISO 50003:2021.
UKAS accredits certification bodies for ISO 50001; ISO itself certifies no one.
UKAS CertCheck lets anyone check a UKAS-accredited certificate.
What certificate dates count for ESOS Phase 4?
The certificate must have been issued on or after 6 December 2023 and still be valid on 5 December 2027.
It must come from a body accredited by UKAS, an EU national accreditation body or another IAF member.
Does ISO 50001 require a percentage cut in energy use?
No. Its scope says it requires demonstration of continual energy performance improvement but does not define levels of improvement to be achieved.
Sources
Where does each figure come from?
Every figure, date and status on this page traces to the instrument’s owner.
Secondary commentary is never the source for a number.
Checked against 16 sources fromISOIAF and ISOUKASlegislation.gov.ukEnvironment AgencyDepartment for Energy Security and Net Zero
- ISOISO 50001:2018 Energy management systems — Requirements with guidance for use
Edition 2, published 20 August 2018, confirmed 13 August 2024; one amendment.
- ISOISO 50001:2018/Amd 1:2024 Climate action changes
Published 23 February 2024; one page, free.
- IAF and ISOJoint Communiqué on the climate action changes (22 February 2024)
The two sentences added to clauses 4.1 and 4.2.
- ISOISO 50003:2021, requirements for bodies certifying energy management systems
Edition 2, May 2021; under systematic review since 5 June 2026.
- ISOISO/IEC 17021-1:2015, requirements for management-system certification bodies
The certification cycle: two-stage initial audit, surveillance, recertification.
- ISOCertification
“ISO does not perform certification or issue certificates.”
- UKASCertification body accreditation
“Energy Management Systems Certification (EnMS) to ISO 50001”, with ISO 50003:2021.
- UKASCertCheck
A free search to verify a claim of UKAS-accredited certification.
- UKASFind an organisation
The directory of accredited certification bodies and their scopes.
- legislation.gov.ukThe Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643), regs 25 and 33
Significant consumption is not less than 95%, measured in energy units or by spend.
- legislation.gov.ukThe ESOS (Amendment) Regulations 2026 (SI 2026/701)
Total or significant consumption; three duties deemed met; DECs and Green Deal Assessments removed.
- legislation.gov.ukSI 2026/701, Explanatory Note
In force 22 July 2026.
- Environment AgencyHow to comply with ESOS phase 4
The certificate window, the accreditation limb, de minimis and the notification duty.
- Department for Energy Security and Net ZeroGovernment response: Climate Change Agreements, consultation on a new scheme (October 2024)
“ISO50001 or other EMS will not be mandatory for the new scheme.”
- Environment Agency and DefraEnergy efficiency standards for industrial plants to get environmental permits
“An energy management system like ISO 50001” or the BREF techniques.
- ISOISO 14001:2026
Published 15 April 2026; ISO 50001 was not revised alongside it.
Continue reading
Where to go next
Guide
ISO 50001 vs ESOS
The certification route against an ESOS energy audit, side by side.
Guide
ESOS Phase 4
Qualification, the audit, the action plan and the dates.
Guide
ISO 14001
The environmental management system standard, now on its 2026 edition.
Guide
UKAS accreditation
How to check a certification body and a certificate.