Complaints about ECO4 and Great British Insulation Scheme work
This page explains what to do if something has gone wrong with insulation or heating work installed under the Energy Company Obligation (ECO4) or the Great British Insulation Scheme (GBIS).
ECO4 runs until 31 December 2026, and GBIS ended on 31 March 2026. Consumer Rights can no longer help with ECO4 applications, but the steps below still apply to work that has already been done.
How ECO4 and GBIS Work
Both schemes require larger energy suppliers to fund energy-efficiency improvements in people’s homes. Ofgem administers them and checks that suppliers meet their obligations. The work itself is carried out by installers, who had to be TrustMark registered.
That matters when something goes wrong: your complaint goes first to the installer that did the work, and then to the energy supplier that funded it.
Before You Complain: Gather Your Paperwork
Pull together everything you have about the work, for example:
- the installer’s name and contact details
- the dates of any survey or assessment and of the installation
- any paperwork showing which energy supplier funded the work
- warranty or guarantee documents and completion certificates
- photos of the problem, and copies of emails, letters and notes of calls
If you don’t know which supplier funded the work, ask the installer.
How to Complain
- Complain to the installer first. Put it in writing, explain what’s wrong and what you want them to do, and give them a reasonable time to respond.
- Then contact the energy supplier that funded the work. If the installer doesn’t resolve it, raise it with the obligated supplier, sending copies of your evidence.
- Check credentials and raise issues with TrustMark. Installers had to be TrustMark registered. You can check an installer on the TrustMark register and raise issues with TrustMark.
- Tell Ofgem. Ofgem says its ability to resolve individual complaints is limited, but it wants to hear feedback, and it has an ECO4 complaints process page on its Energy Company Obligation pages.
Tips for Getting It Resolved
- Keep records of all communication and copies of everything you send.
- Use only TrustMark-registered installers for any remedial work.
- Be wary of cold callers offering to “fix” ECO work or claim compensation for a fee — see how to spot ECO scams.
ECO4 Support Available:
- Department for Business, Energy & Industrial Strategy: Energy Company Obligation
- Ofgem: Energy Company Obligation (ECO4) Guidance: Delivery V1.1
- Ofgem: Energy Company Obligation (ECO)
- UK Government: Help from your energy supplier: the Energy Company Obligation
- Which?: Energy Company Obligation (ECO)
Other Support Available:
People Also Asked
Yes, until 31 December 2026. Ofgem says ECO4 will run until then, following a nine-month extension. Consumer Rights can no longer help with ECO4 applications. The Great British Insulation Scheme ended on 31 March 2026.
The installer that did the work. If they don’t resolve it, contact the energy supplier that funded the work. If you don’t know which supplier that was, ask the installer.
You can:
- complain to the installer, then the energy supplier that funded the work
- check the installer’s credentials and raise issues through TrustMark
- give feedback to Ofgem, which has an ECO4 complaints process page
Keeping records of all communication and documents is strongly recommended.
Ofgem says its ability to resolve individual complaints is limited, but it wants to hear feedback about how the scheme is being delivered. Start with the installer and the energy supplier.