Great British Insulation Scheme vs ECO4

Both schemes have closed to new applications. The Great British Insulation Scheme ran from April 2023 until March 2026 and was not extended. ECO4 stopped accepting new applications after the Chancellor's 2025 Autumn Budget confirmed the end of the green levy, and the scheme itself runs until 31 December 2026 to allow work already committed to be completed¹.

For a household comparing them, the practical difference was always the shape of the offer. ECO4 focused on whole house retrofits for low-income, vulnerable and fuel poor households, while GBIS complemented it by delivering mostly single insulation measures to a wider pool of households in the least efficient homes⁴. Both were funded by energy companies through a levy on bills, not by government grants paid directly to homeowners, and both were administered by Ofgem².

The comparison below sets out how the funding worked, who qualified under each route, what each paid for, how applications ran through suppliers, what the schemes delivered, and what closure means for work already in progress.

GBIS and ECO4 at a glance

The two schemes were designed as a pair, with GBIS explicitly supporting ECO4 rather than replacing it. Ofgem's own description is that GBIS complements the Energy Company Obligation scheme, yet unlike ECO4's whole house approach, it mostly delivered single insulation measures¹. Local authority statements of intent repeat the same framing: GBIS would support ECO4 in the delivery of predominantly single measures targeted at a wider range of households¹¹.

That pairing shaped everything else. ECO4 was launched in 2022 and focused on whole house retrofits, targeting low-income, vulnerable and fuel poor households¹³. GBIS continued ECO4's focus on reducing fuel poverty and energy bills but aimed to deliver rapid installation of energy efficiency measures to a wider pool of households in the least efficient homes¹⁴. Both operated across Great Britain, so England, Scotland and Wales, with separate arrangements in Northern Ireland¹⁵.

The schemes also shared a reputation problem. The National Audit Office found that ECO4 and GBIS combined with the consumer protection and quality assurance system resulted in an overly complex system, with many different actors and no central document clearly setting out how the system should operate¹⁶. In a Commons debate on 17 June 2026, the government stated that ECO4 and GBIS had some of the highest levels of non-compliance that Government have seen⁹.

Two schemes, one levy: how the funding works

Neither scheme was a government grant. ECO4 was funded by energy companies and not by councils, and the Energy Company Obligation places legal obligations on energy suppliers to deliver energy efficiency measures to domestic premises². The money comes from a levy on energy bills, which is why the schemes are described as supplier-funded rather than taxpayer-funded¹⁷.

The obligation has run since 2013, when the first ECO scheme began, and ECO4 is its latest iteration¹⁷. ECO4 was worth £4 billion and was due to end on 31 March 2026 before the extension to 31 December 2026⁵. The government announced in Budget 2025 that funding for ECO would end in March 2026, while energy efficiency measures under the ECO continue until the end of 2026⁷.

A strict rule governed how the money could be combined. Funding for measures delivered under ECO4 cannot be blended with funding from other government schemes or grants, and the same restriction applied to GBIS¹⁹. Funding from the Boiler Upgrade Scheme and ECO cannot be blended for the same measure or be included within an ECO4 project¹³. Any measures outside ECO4 delivered to the same property would have to be installed either before or after the ECO4 measures²². For a household, that meant one funding route per measure, chosen in advance.

Suppliers could move delivery between the two schemes within limits. A supplier could deliver up to 75% of its GBIS obligation through ECO4 projects, and had to deliver at least 25% through GBIS measures²³. ECO4 delivery reassigned to GBIS was subject to a conversion factor of 1.251, meaning £1 of ECO4 delivery equalled £1.251 for GBIS¹⁰. That is an accounting mechanism between suppliers and the regulator, not something a household could use to move its own application.

Who qualifies: ECO4's whole-house route vs GBIS's wider net

ECO4's core route was aimed at low-income, vulnerable and fuel poor households, and it was designed to tackle fuel poverty and help reduce carbon emissions⁶. GBIS cast a wider net: it continued the fuel poverty focus but aimed at a wider pool of households in the least efficient homes, which is why it mostly delivered single measures rather than a full retrofit¹⁴.

Beyond the core routes, both schemes ran Flex routes administered by local authorities. Councils had to publish a statement of intent defining who was eligible for funding before any Flex referrals could happen²⁵. Those statements set local criteria, and they varied. Essex, for example, required residents to live in Essex and be a homeowner, private tenant or landlord, with residents of Southend and Thurrock excluded, and used a household income threshold below £31,000²⁶. Ceredigion's guidance required applicants to own their own home or have the landlord's permission²⁷.

Tenure rules mattered. Under ECO4, a privately rented house generally needed an energy efficiency rating of E, F or G, and the landlord's permission was required²⁸. ECO4 Flex rules were stricter still: private rented sector households had to be in EPC bands E, F or G for all eligible routes²⁹. Premises counted as private domestic premises if they were not owned or let by a social landlord, unless let by the social landlord at or above market rate¹³.

One condition applied throughout: eligibility for ECO4 or GBIS Flex did not guarantee that funding was available¹⁴. A household could meet every published criterion and still receive nothing, because the decision on which projects to fund sat with suppliers.

What each scheme pays for: single measures or the whole house

The clearest dividing line between the two schemes is what they installed. ECO4 focused on whole house retrofits, assessing a property and treating it as a system¹⁴. GBIS mostly delivered single insulation measures, targeting the least efficient homes quickly rather than comprehensively¹.

That difference shows in the measures each scheme supported. GBIS was designed to support ECO4 in delivery of predominantly single measures targeted at a wider range of households, and local authority statements of intent describe it the same way¹¹. Under GBIS, innovation measures scored a 25% or 45% uplift, as applied in ECO4, in the low-income group only²⁹.

ECO4's measure mix was broader. Across the Energy Company Obligation as a whole between 2013 and December 2025, 25% of measures were cavity wall insulation, 21% were new boilers, 18% were loft insulation, 23% were other heating measures mainly new heating controls, 6% were solid wall insulation and 4% were other insulation⁷. Those figures cover the full obligation, not ECO4 alone, but they show the balance between insulation and heating work.

One exclusion is worth noting for anyone comparing routes. Measures approved under the ECO4 DLM route were not eligible for delivery under GBIS⁶. A household could not take a measure approved under one scheme's route and have it installed under the other.

How to apply through your energy supplier

Ofgem administers both schemes but does not accept household applications. Eligible residents needed to contact a participating energy supplier, with the list published on Ofgem's website²⁸. Applications were then made through a TrustMark-registered or approved ECO and GBIS installer¹¹.

The process had a fixed sequence. A survey of the property had to be done to determine suitable measures and certain other criteria, and not all properties were eligible²⁶. Before the first measure was installed, both Section A, covering eligibility, and Section B, the pre-installation survey, had to be completed on the eligibility and pre-installation declaration²⁰. That form exists to confirm the eligibility of properties receiving measures under either scheme and to collect project-level information before installation²⁰.

Suppliers also had to manage their own obligations. They could apply to reassign ECO4 ABS to their GBIS obligation, and from after July 2025 they had to provide an indication of what ECO4 delivery they proposed to reassign to GBIS¹³. A formal request to Ofgem to reassign ECO4 ABS to GBIS was required by 31 July 2026²⁴. Suppliers had to deliver at least 25% of their GBIS total home heating cost reduction obligation through GBIS measures, and could deliver up to 75% through ECO4 projects²⁴.

For a household, the practical consequence was that the supplier, not the council and not Ofgem, decided whether to take the project on. A council could confirm eligibility under a Flex route and still no installer would be funded to carry out the work.

Track record: what has been delivered and where it fell short

The Energy Company Obligation has delivered at scale since 2013: 4.4 million measures in 2.6 million homes across Great Britain between 2013 and December 2025⁷. But ECO4's own delivery fell well short of its predecessors. ECO4 delivered around one-third fewer installations than under ECO3 and almost 70% fewer than ECO1⁷.

Quality was the sharper problem. A small percentage of installations, 6% of external wall insulation and 2% of internal wall insulation, were found to have health and safety risks to the occupants⁸. Around 30,000 homes had defects following external and internal wall insulation installations under ECO4 and GBIS⁸. The government told the Commons that ECO4 and GBIS had some of the highest levels of non-compliance that Government have seen⁹.

The complexity finding explains part of it. The National Audit Office concluded that ECO4 and GBIS combined with the consumer protection and quality assurance system resulted in an overly complex system, with many different actors and no central document clearly setting out how the system should operate¹⁶. Ofgem consulted on mid-scheme changes, and eight respondents disagreed with the proposed approach to the rural data set transition alone²³.

For households, the track record matters less as history than as a warning about what to check on any installation: who carried it out, what guarantee backs it, and whether the work was notified under the correct scheme.

The end of funding and what comes after

The end came in two stages. The government announced in Budget 2025 that funding for ECO would end in March 2026, and energy suppliers stopped advertising or accepting applications for ECO4 funding⁷. Birmingham City Council's announcement is explicit about the cause: following the Chancellor's 2025 Autumn Budget, which confirmed the end of the green levy and consequently the end of ECO4 funding, installer partners could no longer secure funding from energy companies³.

GBIS closed first. It ran from April 2023 until March 2026 and was not extended, unlike ECO4¹. ECO4 was extended to 31 December 2026, following a nine-month extension, and no new applications can be funded². The scheme's published guidance confirms the ending of funding for both the Energy Company Obligation and the Great British Insulation Scheme³⁰.

What replaces them is not set out in the same documents. The Warm Homes Plan and its associated grant programmes are separate schemes with their own eligibility rules, and the funding blending restriction means a household cannot combine a closed ECO4 measure with a new grant for the same work¹⁹. For anyone who missed the window, the practical position is that the supplier-funded route to insulation has ended, and any future support comes through different programmes with different criteria.

What closure means for applications already in progress

Work already committed can still be completed. ECO4 runs until 31 December 2026, and installation extensions will not allow installation dates beyond that overall scheme deadline²⁴. Suppliers can carry over measures with either PAS2017 or PAS2019 standards, and administration moved to the PAS2035:2023 and PAS2030:2023 standards from the end of the transition period on 30 March 2025²³.

The conversion rules still apply to work in the pipeline. ECO4 delivery reassigned to GBIS is subject to a conversion factor of 1.251, and suppliers had to formally request reassignment by 31 July 2026²⁴. A measure does not count as a qualifying action on ECO4 if it has been notified under the Great British Insulation Scheme, so a project cannot be moved between schemes after notification¹³.

If an installation turns out to be defective, the route to remedy survives the scheme. Original installers are liable for fixing the installation, and costs of up to £20,000 should be covered by a guarantee when the installer has ceased to trade or failed to remediate⁸. Families affected should first contact the installer who carried out the installation, and where the installer is no longer trading or unable to remedy damages, they can contact their guarantee provider to initiate a claim⁹. The government has acknowledged that the cost of damage from faulty ECO4 and GBIS solid wall insulation can exceed the £20,000 limit covered by a valid guarantee⁹.

For a household's energy independence, the legacy of both schemes is a better insulated building fabric, which reduces the heat needed to keep a home warm and therefore reduces reliance on bought energy. What neither scheme removed is the underlying dependence: the work was funded by a levy on bills, delivered by a supplier's chosen installer, and backed by a guarantee that only pays out up to a fixed limit. The insulation stays with the house; the funding mechanism, and the risk that sits with it, does not.