Great British Insulation Scheme vs ECO4

Scheme status and eligibility rules in this comparison were checked on 22 July 2026. Historical budgets, delivery and remediation figures retain the date stated with them.

The Great British Insulation Scheme (GBIS) and the Energy Company Obligation in its fourth phase (ECO4) are two government energy-efficiency schemes for Great Britain. Both place an obligation on medium and large energy suppliers to fund and arrange measures in less energy-efficient homes, both are administered by Ofgem with policy set by the Department for Energy Security and Net Zero (DESNZ), and both ran at the same time. GBIS mostly delivered a single insulation measure to a broad range of households. ECO4 funds a whole-house retrofit, a package of measures worked out together, for low-income and vulnerable households.

GBIS ran from April 2023 (the scheme consulted on as ECO+, renamed on launch), with a £1 billion budget. Its legal name is ECO4A, established by the Electricity and Gas (Energy Company Obligation) Order 2023 to operate alongside ECO4. Installations had to be complete by 31 March 2026, and the online eligibility checker on GOV.UK has closed. ECO4 came into force in July 2022, applies to measures installed from 1 April 2022 and carries a £4 billion budget. It works through a Home Heating Cost Reduction Obligation (HHCRO), which requires obligated suppliers to promote measures that help low-income, fuel-poor and vulnerable households heat their homes.

	GBIS	ECO4
Legal name	ECO4A	ECO4
Ran from	April 2023	April 2022
Budget	£1 billion	£4 billion
Approach	Single insulation measure	Whole-house retrofit
Who qualified	EPC (Energy Performance Certificate) D-G with a lower council tax band, or a qualifying benefit	A qualifying benefit, or ECO4 Flex
Measures	Insulation, plus heating controls for low-income owners	Insulation, heat pumps, boiler upgrades, storage heaters, solar
Minimum SAP (Standard Assessment Procedure) gain	None	Required

Who qualified: benefits, income and EPC band

GBIS had two routes in. The low-income group covered homeowners and tenants receiving at least one qualifying benefit, such as Universal Credit, Pension Credit, Housing Benefit, Income Support or income-related Employment and Support Allowance. The general group was the wider one: households with an EPC rating of D to G, in council tax bands A to D in England or A to E in Scotland and Wales. The general group is what let GBIS reach households that ECO4 would not, since it did not depend on receiving benefits. GBIS also had its own local-authority flex route, letting a council refer residents into the scheme.

ECO4 eligibility is narrower and aimed at fuel poverty. The main route is the same benefits list. Beyond that, ECO4 Flex lets a local authority refer a household that does not receive those benefits but meets an alternative test: a combined gross annual household income under £31,000, or a household member with a health condition made worse by living in a cold home, such as a cardiovascular condition, a respiratory disease, limited mobility or a suppressed immune system. Energy suppliers can also refer households struggling with persistent fuel debt or on prepayment meters that disconnect regularly.

Meeting the criteria did not guarantee an installation. Ofgem states that GBIS eligibility does not commit a supplier or installer to fit measures in a given home.

What each scheme paid for

GBIS focused on single insulation measures. Both eligibility groups could get cavity wall insulation (including party wall), loft, solid wall, pitched roof, flat roof, under-floor, solid floor, park home or room-in-roof insulation. For owner-occupiers in the low-income group, certain heating controls such as room thermostats and boiler programmers were allowed as a secondary measure alongside the insulation. Mid-scheme changes announced in June 2025 raised the limit from one insulation measure to two, and added smart thermostats for owner-occupied low-income households. The official figures to November 2024 record around 53,400 measures across roughly 42,600 households, against the £1 billion budget. Of those measures, cavity wall insulation made up 42%, loft insulation 28% and heating controls 20%, with the rest covering solid wall, underfloor and other types.

ECO4 covers a wider range because it is built around the whole house. As well as insulation, it can fund heat pumps, boiler upgrades, electric storage heaters and heating controls. It can in some cases fund solar PV panels as part of the wider package, though insulation and heating remain the core measures. ECO4 requires a measure to deliver a minimum improvement in a property’s SAP energy rating. GBIS set no such minimum, so an eligible insulation measure could go ahead without a required SAP uplift.

Both schemes could also fund Ofgem-approved innovation measures outside the standard list, technologies or methods signed off case by case. Under GBIS this route was limited to the low-income group and social housing.

Both schemes hold installers to the same quality framework. Work must meet the PAS 2030 and PAS 2035 installation standards, and the installer must be a TrustMark-registered business. Ofgem uses data shared by TrustMark to check compliance against the scheme rules.

Getting both, and the co-funding rule

The two schemes were designed to complement each other rather than compete. ECO4 concentrated on low-income and vulnerable households; GBIS added the general EPC-and-council-tax route on top, widening the reach to homes that ECO4 did not serve.

A household cannot receive funding from two government schemes for the same measure. The restriction bites at the measure level, not the property level. Loft insulation already funded through ECO4, GBIS or a grant such as the Home Upgrade Grant cannot then be funded again by another of those routes. A household could in principle have one measure funded through one scheme and a different measure through another, provided the funding does not overlap on the same work.

Behind the scenes, the June 2025 mid-scheme changes let suppliers reassign some ECO4 delivery towards their GBIS target, so certain ECO4 work could count against the GBIS obligation. That is a supplier-accounting change and does not alter what an individual household can claim.

The solid wall insulation failures and the 2025 audit

A National Audit Office (NAO) report published in October 2025 found systemic problems with solid wall insulation fitted under both schemes. DESNZ and Ofgem believe that nearly all external wall insulation (EWI) installed under ECO4 and GBIS has major issues needing remediation, around 98% on their assessment. About 29% of internal wall insulation (IWI) was found to have major issues. The report estimated that 22,000 to 23,000 homes need EWI remediation and 9,000 to 13,000 need IWI remediation, up to around 36,000 in total. It also found that 6% of EWI installations posed immediate health and safety risks. Remediation costs were put at anywhere from £250 to £18,000 per property, with extreme cases reaching £250,000.

The figure describes EWI fitted under these two schemes specifically. It is not a statement about all solid wall insulation in the UK, nor about earlier phases of the Energy Company Obligation, and it reflects the government’s overall assessment of these installations rather than the result of a random-sample audit. By mid-September 2025, only around 8% of the EWI homes and 10% of the IWI homes identified for remediation had been fully put right, and no completion timetable was in place. The government said remediation would be carried out at no cost to the homeowner.

The report also set out a fraud problem. Ofgem estimates that retrofit businesses falsified claims for ECO installations in between 5,600 and 16,500 homes, potentially claiming £56 million to £165 million from energy suppliers. The NAO attributed the failures to poor-quality installation, weak government oversight and inadequate audit and monitoring, across a system with fragmented roles split between DESNZ, Ofgem and others. The consumer protection system introduced in 2021 did not flag the wall insulation problems until late 2024. In response the government suspended 38 installers and committed to centralised oversight and full remediation.

Applying, and the cold-caller problem

The route into GBIS was to contact an energy supplier, since the central GOV.UK eligibility checker has closed. The supplier arranged an assessment of the property, after which the household learned whether it needed to contribute anything towards the cost. GBIS was not a grant scheme, so a contribution could be required, and higher-cost work such as solid wall insulation was more likely to need one. A household that disagreed with the assessment or the cost could decline before any work went ahead. All installations had to finish by 31 March 2026. ECO4 works similarly but with the wider measure list, and local authorities can bring households in through ECO4 Flex.

Suppliers did not all offer the full measure list: some accepted only cavity wall and loft insulation and turned down solid wall applications, and waits of several weeks to several months were common between application and an installer visit. Cold-calling and leaflet drops from firms with no website or online presence are a recognised pattern around these schemes, alongside reports of inflated quotes and follow-up approaches claiming ventilation faults from insulation that was never fitted. Verifying any approach directly through your own energy supplier is the safe way to check whether an offer is genuine.

What this means if you are planning a heat pump

Insulation and a heat pump are linked through heat loss. A better-insulated home loses less heat, so it needs a smaller heat pump and runs it more efficiently, which is why insulation comes first in most heat pump planning. ECO4 can fund a heat pump directly, as part of a whole-house package that pairs it with insulation. GBIS delivered insulation on its own, with no heating system attached.

GBIS insulation changes how much heat a property loses, but the scheme installs insulation, not the room-by-room heat-loss survey a heat pump needs for sizing. That survey is a separate exercise. Poorly fitted solid wall insulation, the failure the NAO report identified, can trap moisture and cause damp and mould, which undermines the fabric-first basis a heat pump design relies on.

The Warm Homes Plan and the end of both schemes

GBIS installations closed on 31 March 2026. The government’s final response to the ECO4 consultation extended ECO4 by nine months to 31 December 2026. That is the operative end date; no new GBIS applications are being taken.

The successor framework is the Warm Homes Plan, published on 21 January 2026 and updated in March 2026. For individual households in England, the main route it sets out is the Warm Homes: Local Grant, funding for local authorities to deliver energy performance and low-carbon heating upgrades to low-income homes. That grant replaces the Home Upgrade Grant, which has closed. GBIS and ECO4 were supplier-obligation schemes, where the government set targets and energy suppliers funded and arranged the work. The Warm Homes: Local Grant is a grant programme run through local authorities, a different delivery model for government-funded retrofit.