The Great British Insulation Scheme

The Great British Insulation Scheme (GBIS), formerly known as ECO+, was a government energy-efficiency scheme that placed an obligation on medium and large energy companies to deliver insulation, and in some cases heating controls, to homes across Great Britain¹. It was designed to improve the least energy-efficient homes, help tackle fuel poverty and reduce carbon emissions, and it mostly delivered a single insulation measure per home, unlike the whole-house approach of the ECO4 scheme it complemented¹. The scheme began in April 2023, installations had to be complete by 31 March 2026, and the service to check eligibility on the gov.uk portal has now closed².

The scheme was expected to cost £1 billion and to help around 300,000 households⁴. Up to the end of December 2025, 126,000 measures had been installed⁴. This page explains who qualified, what was funded, how the work was delivered and guaranteed, how the nations differed, and what the scheme did and did not achieve for household energy independence.

One measure per home, funded by energy suppliers

The scheme worked by placing an obligation on medium and large energy companies to deliver measures that reduce energy usage¹. It was administered by Ofgem, which sets targets for obligated suppliers, ensures compliance and monitors progress⁶. Unlike ECO4, which requires a whole-house retrofit for eligible homes, GBIS was predominantly a single measure scheme, with extra measures eligible only under certain conditions¹. Compliance was measured on an annual basis rather than across a multi-year period⁸.

The scheme's stated purpose was to deliver improvements to the least energy-efficient homes in Great Britain, to help tackle fuel poverty and reduce carbon emissions⁶. It complements the Energy Company Obligation, and specifically ECO4, which runs on a whole-house basis for households on low incomes¹. GBIS extended help beyond ECO4's benefits-led eligibility by adding a general group defined by council tax band and energy performance rating, which is what made it a wider scheme than ECO4 alone⁴.

The scheme also included incentives to support the delivery of innovative measures that can provide further energy efficiency improvements or offer additional benefits⁶. Only obligated suppliers could apply under the innovation routes: a manufacturer or installer with a new or innovative product or system had to work with an obligated supplier, which liaised with Ofgem and submitted the application⁹. The award of the innovation uplift was capped at 10% of a supplier's low-income group obligation¹⁰.

Progress on installations: 126,000 measures versus 300,000 homes

The headline numbers are straightforward. The scheme was designed to help around 300,000 households and was expected to cost £1 billion⁴. Up to the end of December 2025, 126,000 measures had been installed⁴. The total cost of compliance with the obligation was estimated at £1.02 billion in the government's final stage impact assessment for the mid-scheme changes¹¹.

Of the measures installed up to the end of December 2025, 38% were cavity wall insulation, 28% loft insulation, 25% heating controls and 4% solid wall insulation⁴. The dominance of cavity wall and loft work reflects the scheme's design: it was built for the rapid installation of value-for-money insulation measures, and those two measures are the cheapest and quickest to fit⁹. Solid wall insulation, which is far more expensive and disruptive, made up a small share.

The Department for Energy Security and Net Zero published monthly statistics covering measures installed and households upgraded, analysed by measure type and geographical region¹². Data in the monthly releases was published two months in arrears, and the figures were provisional and subject to future revisions¹². Final figures up to the end of the scheme were published in the May 2026 publication¹³.

The cost of the scheme fell on energy bills rather than general taxation. The scheme was estimated to add £5 to a typical annual dual fuel bill in 2023/24 and £17 in each of the following two years⁴. Ofgem also publishes monthly reports showing supplier progress towards their targets and the number and types of measures installed¹⁴.

Eligibility: two groups, and what each had to show

The scheme had two eligibility groups, and a household only needed to qualify under one of them.

• The low-income group was for homeowners or tenants who received at least one of the following benefits: Child Benefit, Pension Guarantee Credit, income-related Employment and Support Allowance, income-based Jobseeker's Allowance, Income Support, Universal Credit, Housing Benefit, or Pension Credit Savings Credit³.
• The general group was for households with properties that had an EPC rating of D to G, in Council Tax bands A to D in England or A to E in Scotland and Wales³. This was the group that extended the scheme well beyond the benefits-tested population⁴.

Beyond the group test, there were property and tenure conditions. The property had to require energy-efficiency upgrades such as cavity wall insulation, decided through a retrofit assessment, and the householder had to own their own home or have permission from their landlord, including social housing providers or management companies³. Eligibility did not guarantee that an energy supplier or installer would decide to install measures: it was up to the energy companies to determine which retrofit projects they funded and at what level³.

There was no minimum requirement for a property's Standard Assessment Procedure (SAP) rating to be increased through the measure, which distinguished GBIS from ECO4's minimum-improvement conditions⁹. More detail on the two groups is on the GBIS eligibility page, and the benefits that open the low-income route are listed on which benefits qualify for energy grants.

What was covered by funding and typical household costs

Both the general and low-income groups were eligible for the same list of insulation measures³:

• Cavity wall (including party wall)
• Loft
• Solid wall
• Pitched roof
• Flat roof
• Under-floor
• Solid floor
• Park home
• Room-in-roof

Where an eligible insulation measure was installed in owner-occupied premises in the low-income group, certain heating controls, such as room thermostats, were also allowed as a secondary measure³. Heating controls accounted for 25% of all measures installed, which shows how significant this secondary route became in practice⁴.

The scheme delivered free or cheaper insulation to reduce home energy bills, but "free" was not guaranteed². It was up to the energy companies to determine which retrofit projects they chose to fund and the level of funding, which depended on the measure type and other factors³. Higher-cost measures, such as solid wall insulation, were more likely to require a contribution from the household³. A household found out after the property assessment whether they needed to pay anything towards the installation, and could decide not to go ahead if they did not agree with the assessment or the costs².

One rule mattered for households hoping to stack grants. Funding for measures delivered under the scheme could not be blended with funding from other government schemes or grants, including the Warm Home Discount, the Home Upgrade Grant, the Boiler Upgrade Scheme, the Social Housing Decarbonisation Fund and ECO4⁸. Non-scheme measures had to be installed before or after all scheme measures³.

Quality rules, fitting firms and guarantees

All measures available under the scheme had to be delivered according to PAS 2030 and PAS 2035 standards⁹. All installers had to be TrustMark-accredited and had a registration number, so a householder could verify the business before work began³.

The guarantees position is worth stating plainly. Ofgem administers the scheme but does not administer appropriate guarantees or financial protection for measures installed under it⁹. The current list of appropriate guarantees can be found on the TrustMark website⁹. A householder's recourse for a faulty installation runs through the installer and its guarantee, and through the complaints process, not through Ofgem's own protections.

For cavity wall work there is a further building control dimension. The installation of cavity wall insulation is specifically defined as notifiable building work in the Building Regulations, which means a building notice must be submitted to a building control body stating that the work will be carried out¹⁵. If the installer is registered with the Cavity Insulation Guarantee Agency, the installer will in most cases submit the building notice, but building owners should always check that a building notice will be submitted¹⁶. The Building Regulations also require that the insulation material used is suitable for the wall construction concerned, and for some foam cavity wall insulating materials an assessment of the risk of formaldehyde gas emission must be carried out¹⁶.

Complaints about an installation were handled under a defined complaints process, and Ofgem's role was limited: it set targets for obligated suppliers, ensured compliance and monitored progress, but had no oversight of contractual arrangements between householders and suppliers or installers, and its ability to help resolve complaints was limited³. Suspected fraud could be reported via Ofgem's counter fraud section¹⁴.

Differences across the UK

The scheme applied to England, Scotland and Wales⁷. Northern Ireland was never part of it: the obligation ran in Great Britain only, and households in Northern Ireland look instead to the Northern Ireland Sustainable Energy Programme and the Affordable Warmth Scheme, covered on the Northern Ireland energy grants page.

Within Great Britain, the main difference was the council tax band test for the general group: bands A to D in England, but A to E in Scotland and Wales³. The EPC requirement of D to G was the same across the three nations³.

The building rules that sit behind the measures also differ by nation. Cavity wall insulation is notifiable building work under the Building Regulations in Wales as in England¹⁵, and where a solid wall is upgraded by the installation of insulation in Wales it must meet the minimum energy efficiency values set out in the Approved Documents, or, where such an upgrade is not technically or functionally feasible, be upgraded to the best standard achievable within a simple payback of no greater than 15 years¹⁵.

Delivery was not evenly spread, and the monthly statistics analysed installations by geographical region, so households comparing uptake could see how their area performed¹².

What the measures involve: cavity, loft and solid wall

Cavity wall, loft and solid wall insulation were among the most common measures delivered, so it is worth knowing what each involves.

Cavity wall insulation is blown into the cavity from the outside, disruption to the householder is minimal, and the work can take just a couple of hours for a typical three-bedroom house¹⁷. The main materials used are mineral wool (glass or rock wool), EPS bead (polystyrene bead) and PU foam (polyurethane foam)¹⁰. Cavity wall measures under the scheme were differentiated by the thermal conductivity of the insulation, with variants at 0.040, 0.033 and 0.027, plus a partial fill measure and a party wall cavity measure⁵. Where at least 50% of the cavity walls were originally insulated prior to retrospective insulation, the partial fill measure applied¹⁰. Uninsulated cavities can add up to 25 per cent onto a heating bill¹⁷.

Loft insulation was the second most common measure at 28% of installations⁴. Loft work is the classic value-for-money measure the scheme was designed around.

Solid wall insulation can be applied externally, as a decorative, weatherproof insulating treatment on the outside of the walls, or internally, using ready-made insulation boards, insulation and plasterboard laminates, or wooden battens in-filled with insulation¹⁹. External insulation thickness needs to be between 50 and 100mm, and insulation and plasterboard laminates typically total up to 90mm¹⁹. Solid walls lose even more heat than cavity walls¹⁹. Solid wall insulation can be expensive, so the ideal time to do it is when walls need other corrective work; external insulation is usually installed where there are severe heating problems or the exterior of the building requires other repair work¹⁶. It accounted for only 4% of measures⁴.

For party wall measures, the installer had to obtain the necessary consent from all properties adjacent to the wall before the measure was carried out⁸.

Late applications and what is left

The scheme has closed. The service to check eligibility on the gov.uk portal has closed, and installations had to be complete by 31 March 2026, when the scheme ended². Some energy suppliers were still accepting applications after the portal closed, so the position was to check with your supplier². Households with questions about an existing application were told to contact the energy supplier they applied to².

For households who missed the scheme, the routes that remain are the successor and parallel schemes. ECO4 runs to March 2026 alongside GBIS and offers whole-house retrofit for low-income households, described on the ECO4 and ECO4 eligibility pages. The Warm Homes: Local Grant and Warm Homes: Social Housing Fund cover the successor landscape, and the comparison of the Warm Homes: Local Grant and GBIS sets out the differences. The full picture of what is open and closed is on the home energy grants pillar page and the closed home energy grants page.

Contact routes that remain live: Ofgem's GBIS team could be reached at GBIS.enquiry@ofgem.gov.uk¹⁴, and the scheme helpline was 0800 098 7950, open Monday to Friday 8am to 6pm and Saturday 9am to 12pm²⁰. Contact details of obligated suppliers were published on Ofgem's site¹⁴.

What GBIS did, and did not do, for energy independence

GBIS delivered a real but narrow gain. A single insulation measure, funded by an obligated supplier, permanently reduces the heat a home loses, which cuts the amount of energy the household must buy and lowers its exposure to price rises. Cavity wall insulation alone can remove up to a quarter of the heating bill penalty from uninsulated cavities¹⁷. For the households that received it, that is a durable reduction in dependence on energy purchases.

The limits are equally clear. The scheme delivered one measure per home, so most recipients got a single intervention rather than a whole-house upgrade: a home with insulated cavity walls but an uninsulated loft and an old boiler remains largely dependent on its supplier and on gas¹. The delivery figures show the gap between ambition and outcome: 126,000 measures against a target of around 300,000 households⁴. Solid wall insulation, the measure that matters most for the hardest-to-treat homes, was 4% of delivery⁴.

The scheme also created its own dependencies. The householder's counterparty was an energy supplier deciding what to fund, not a right to a grant³. The guarantee sat with the installer and TrustMark, not with Ofgem⁹. The funding came from levies on everyone's bills, £5 on a typical dual fuel bill in 2023/24 and £17 in each of the two following years, so the scheme redistributed rather than created independence⁴. And because GBIS funding could not be blended with other government schemes, a household planning a fuller retrofit, such as insulation alongside a heat pump through the Boiler Upgrade Scheme, had to sequence the work rather than combine it⁸.

For a household weighing what insulation still does for independence, the wider picture is on the grants and energy independence page.