Background
The Energy Company Obligation 4 (ECO4) is a government scheme designed to tackle fuel poverty and reduce carbon emissions by requiring larger energy companies to install energy-saving measures such as insulation in homes. The Great British Insulation Scheme (GBIS) also promotes energy efficiency installations and operates in a similar way to ECO4, but has broader eligibility. Both schemes are funded via energy consumers’ bills.
In January 2025, the government announced it had become aware of issues with these schemes, including for example poor-quality solid wall insulation installations. These issues were identified by TrustMark, the not-for-profit company responsible for the quality assurance of installations under the schemes.
The issues ranged in severity from insufficient ventilation and missing or exposed insulation, which could lead to damp and mould, to missing or incomplete paperwork. The Department for Energy Security and Net Zero (DESNZ) suspended 38 installation businesses, expanded checks of insulation measures, and implemented a plan for remediation.
Scope
This factual investigation will focus on how DESNZ and Ofgem have identified and responded to issues within the ECO4 and GBIS schemes. It will set out:
- how the ECO4 and GBIS schemes are intended to work
- what issues the government is aware of
- how it is responding
- what lessons the government has learnt and applied
NAO team
Director: Joshua Reddaway
Audit Manager: Mark Bisset