Sources: Ofgem, homeowners and tenants; Ofgem LA guidance v3.0, sections 5.4-5.5. Checked 30 October 2026.
Why the assessment matters so much
ECO4's EPC rule (D to G for owner-occupied homes, E to G for private rented, under the benefits route and most Flex routes) is applied to the home as assessed, not to an old certificate. Ofgem's local authority guidance says councils do not check the SAP band or tenure: installers determine whether a property meets those requirements after their initial SAP or RdSAP assessment, then decide the measures and which scheme to use. It adds that consumers should be told their eligibility may be affected by the outcome. So if your old EPC says E but the assessment rates the home C, ECO4 may not go ahead.
The stages, from checker to installation
| Stage | What happens | Your check |
|---|---|---|
| 1. Eligibility check | Benefit or Flex route confirmed by the supplier, installer or council | Keep award letters and any council declaration |
| 2. SAP / RdSAP assessment | The home's energy rating is assessed | Ask for the result and the band |
| 3. Retrofit assessment | The measures that would benefit the home are identified | Ask why each measure is recommended |
| 4. Contract | The supplier decides what to fund; you get the terms | Check measures, any contribution, guarantees |
| 5. Installation | A TrustMark-registered installer does the work | Check the business on the TrustMark register |
How to prepare for the visit
- Clear access to the loft hatch, boiler, meters and any heaters.
- Have your benefit award letter, or council Flex declaration, to hand.
- Know roughly how old the boiler or heaters are, and any problems with damp or cold rooms.
- If you rent privately, have your landlord's written permission ready (GOV.UK requires the owner's permission).
- If you are helping an older relative, be there for the visit.
Questions to ask the assessor
- What SAP band did the home come out as, and does it still meet the ECO4 rule?
- Which measures are you recommending, and why?
- Which obligated supplier is funding this?
- Will I be asked to contribute anything? (Ofgem says this can happen.)
- Which TrustMark-registered business will install it, and what guarantee comes with it? (See how to find an ECO4 installer.)
After the assessment
Ofgem's advice is to agree to ECO measures only once you have received a contract, and to shop around if you are approached by several companies. ECO4 cannot be blended with other government grants for the same measures, so mention any other scheme you have applied for. If you are unhappy with work afterwards, GOV.UK says to contact the installer or the company that guaranteed the work, then Citizens Advice. Read how to apply for ECO4 for the full process, and is ECO4 really free on contributions.
Timing
ECO4 runs until 31 December 2026, and Ofgem frames its dates around installation. Assessments and contracts take time, so book early (see is ECO4 still available). Check if you might qualify with the checker on this page, or read the ECO4 eligibility rules first.
Questions
What is an ECO4 retrofit assessment?
Ofgem says the measures that would benefit a home are determined by a retrofit assessment. It includes a SAP or RdSAP assessment of the home's energy rating, carried out by or for the installer.
Can the assessment change whether I qualify?
Yes. Ofgem's guidance says installers determine SAP band and tenure eligibility after their SAP or RdSAP assessment, and consumers should be told their eligibility may be affected by the outcome.
Do I have to agree to everything the assessor recommends?
No. Ofgem says only agree to ECO measures once you have received a contract, and you may be asked to contribute, so ask what is included before you sign.
Who carries out the work?
A TrustMark-registered installer. You can check any business on the TrustMark register.