The Great British Insulation Scheme

The Great British Insulation Scheme, formerly known as ECO+, was a government energy-efficiency obligation placed on medium and large energy companies to deliver measures that reduce energy usage in the least energy-efficient homes in Great Britain¹. It ran from 25 July 2023 to 31 March 2026 and closed on that date². Unlike ECO4's whole house approach, it mostly delivered single insulation measures, one per home, so that as many households as possible could be reached quickly¹.

Its defining feature was the general eligibility group: households did not have to be on benefits. A property with an Energy Performance Certificate rating of D to G, in council tax bands A to D in England or A to E in Scotland and Wales, could qualify⁴. A separate low-income group covered homeowners and tenants receiving one of a list of qualifying benefits, and could also receive certain heating controls as a secondary measure⁴.

GBIS was estimated to be a £1 billion obligation on energy suppliers, with the previous government forecasting that 300,000 households would benefit by 2026⁵. Actual delivery fell well short of that: 126,000 measures were installed up to the end of December 2025⁷. The scheme is administered by Ofgem, which sets supplier targets and monitors progress but does not administer guarantees for the work⁵.

The scheme in one paragraph: a single-measure, supplier-funded insulation obligation

GBIS worked by placing an obligation on medium and large energy companies to deliver measures that result in reduced energy usage¹. It complemented ECO4 rather than replacing it, and was designed to deliver improvements to the least energy-efficient homes in Great Britain, to tackle fuel poverty, reduce energy bills and reduce carbon emissions¹. Where ECO4 requires a package of works assessed against a whole-house standard, GBIS was predominantly a single measure scheme with extra measures being eligible under certain conditions¹⁰. The focus was solely on the delivery of insulation and heating control measures¹¹. Ofgem describes the approach as the rapid installation of value-for-money insulation measures and, in some cases, heating controls⁸. Compliance was measured on an annual basis, rather than across the scheme as a whole¹⁰. For a side-by-side treatment of the two obligations, see Great British Insulation Scheme vs ECO4, and for the wider framework, the Energy Company Obligation.

Delivery figures: 126,000 measures against a 300,000-household target

There were 126,000 measures installed under the scheme up to the end of December 2025⁷. Of those, 38 per cent were cavity wall insulation, 28 per cent loft insulation, 25 per cent heating controls and 4 per cent solid wall insulation⁷. Heating controls accounting for a quarter of delivery is notable in a scheme described as an insulation scheme: controls were permitted only as a secondary measure alongside an eligible insulation measure in owner-occupied low-income homes⁴.

Against the forecast that 300,000 households would benefit by 2026, delivery of 126,000 measures represents a substantial shortfall, and because a single household can receive an insulation measure plus a heating control, the number of households reached is lower than the number of measures⁶. The scheme was expected to cost £1 billion⁷.

Statistics were published monthly, covering measures installed and households upgraded, analysed by measure type and geographical region, and applying to England, Scotland and Wales¹². Data in each monthly release were two months in arrears, and the figures are provisional and subject to future revisions¹². Final figures up to the end of the scheme were published in the May 2026 publication¹⁴. Ofgem also publishes monthly reports showing supplier progress towards targets and the number and types of measures installed, and has stated an intention to add GBIS to its supplier performance reporting¹⁵.

Eligibility: two groups, and four routes into the scheme

Eligibility ran through four routes: General Eligibility, Low-income and Social Housing, In-fill, and LA Flex¹⁷. In practice households encountered two groups.

The general group covered households whose property had an EPC rating of D to G and sat within council tax bands A to D in England or A to E in Scotland and Wales⁴. This was the widest eligibility test used by any recent supplier-funded scheme, and it is what distinguished GBIS from ECO4.

The low-income group covered homeowners or tenants receiving at least one of: 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 Credit⁴. Related detail sits on which benefits qualify you for energy grants and GBIS eligibility.

Beyond the group test, several conditions applied:

• The property had to require energy-efficiency upgrades such as cavity wall insulation, decided through a retrofit assessment⁴.
• The applicant had to own the home or have permission from the landlord, including social housing providers or management companies⁴. Homeowners, landlords and tenants were all within scope¹⁸.
• There was no minimum requirement for a property's Standard Assessment Procedure rating to be increased through the measure, unlike ECO4's scoring rules⁸.
• Local authorities referring eligible households had their own set of requirements under separate Ofgem guidance¹⁹.

Measures funded, and what a household might have paid

Both the general and low-income groups were eligible for cavity wall insulation including party wall, loft insulation, solid wall insulation, pitched roof, flat roof, under-floor, solid floor, park home and room-in-roof insulation⁴. 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 measure⁴.

Funding was not uniform. The cost of measures could be partially or fully subsidised, depending on the proposed measure and any property issues²⁰. Higher-cost measures, such as solid wall insulation, were more likely to need a contribution from the household⁴. That, together with the cost position of solid wall work generally, helps explain why solid wall insulation was only 4 per cent of measures delivered while cavity wall was 38 per cent⁷.

Funding for measures delivered under the scheme could not be blended with funding from other government schemes or grants, including the Warm Home Discount, Home Upgrade Grant, Boiler Upgrade Scheme, Social Housing Decarbonisation Fund and ECO4¹⁰. Non-scheme measures had to be installed before or after all scheme measures⁴. This matters for anyone who combined works: see can ECO4 measures be funded with other government grants and the wider grants and schemes guide.

Separate incentives supported innovative measures that could provide further energy efficiency improvements or offer additional benefits, but only obligated suppliers could apply under the innovation routes; a manufacturer with a new product had to work with an obligated supplier, which liaised with Ofgem and submitted the application⁹. Award of the innovation uplift was capped at 10 per cent of a supplier's low-income group obligation, and the 5 per cent applicant uplift did not apply under GBIS²¹. Measures approved under the ECO4 DLM route were not eligible for delivery under GBIS, while ECO4 approved innovation measures could be delivered where GBIS measure type and eligibility requirements were met²¹.

Standards, installers and who stands behind the work

All measures available under the scheme had to be delivered according to PAS2030/2035 standards, and all installers had to be a TrustMark-registered business with a registration number⁴. The delivery guidance required work to be carried out in accordance with relevant provisions of PAS 2030:2019, PAS2035:2019, building regulations and any other applicable regulations¹⁰. Where a party wall measure was involved, the installer had to obtain the necessary consent from all properties adjacent to the wall before the measure was carried out¹⁰.

Ofgem's position on redress is explicit and important for anyone holding a GBIS installation:

The current list of appropriate guarantees is held on the TrustMark website⁸. Ofgem sets targets for obligated suppliers, ensures compliance and monitors progress, but has no oversight of contractual arrangements, and says its ability to help resolve a complaint is limited⁴. Complaints about an installation follow Ofgem's energy company obligation complaints process¹⁵. Suspected fraud can be reported through Ofgem's counter fraud route¹⁵. There are quality issues with some solid wall insulation fitted through the scheme³. Related reading: do ECO4 installations need a TrustMark registered installer and energy grant scams.

How the nations differ

The scheme applied to England, Scotland and Wales¹³. Northern Ireland was outside it, and households there rely on separate provision; see home energy grants in Northern Ireland.

Building control requirements also vary. In Wales, the guidance is that where a solid wall is upgraded by the installation of insulation it must meet the minimum energy efficiency values set out in the Approved Documents, and where such an upgrade is not technically or functionally feasible the element should be upgraded to the best standard which can be achieved within a simple payback of no greater than 15 years²⁴. Scottish households also have access to separate support: Home Energy Scotland offers loft, cavity and underfloor insulation funding of £500 per improvement as a loan alongside a £1,500 grant per improvement²⁵. That support sits outside GBIS and is covered in home energy grants in Scotland and home energy grants in Wales.

The measures themselves: what cavity, loft and solid wall work involve

Cavity wall insulation dominated delivery, and the reason is practical. The insulation is blown into the cavity from the outside and disruption to the householder is minimal, in a process that can take just a couple of hours for a typical three-bedroom house²⁶. Cavities that are not insulated can add up to 25 per cent onto a heating bill²⁶. Ofgem's measure definitions distinguish cavity wall insulation by thermal conductivity, at 0.027, 0.033 or 0.040, alongside partial fill and party wall cavity variants, with a U-value target of 0.55 W/m2K; the main materials used are mineral wool (glass or rock wool), EPS bead (polystyrene bead) and PU foam (polyurethane foam)²¹. A partial fill measure applies where at least 50 per cent of the cavity walls are originally insulated prior to retrospective insulation²¹. Insulation should go at least 150mm below the damp proof course level²⁷.

Solid walls lose even more heat than cavity walls, and the options are a decorative, weatherproof insulating treatment on the outside of the walls or ready made insulation boards internally²⁸. External insulation thickness needs to be between 50 and 100mm; internal insulation/plaster board laminates are typically up to 90mm in total²⁸. Internal types include ready made insulation/plaster board laminates, wooden battens in-filled with insulation, or flexible linings²⁸. External work is usually installed where there are severe heating problems, or where the exterior requires other repair work providing the opportunity of adding insulation²⁸. Solid wall insulation can be expensive, so the ideal time to do it is when the walls need some other corrective work²⁶. Beyond bills, it helps create a more even temperature in the home, helps prevent condensation on walls and ceilings, and can reduce heat building up inside during summer hot spells²⁸. For planning purposes, the installation of solid wall insulation constitutes an improvement rather than an enlargement or extension to the house²⁹.

Published cost and saving estimates vary and are not official scheme figures. Independent guidance puts cavity wall insulation for a semi-detached house at around £2,700 to install with savings of £240 a year, while another independent estimate for 2026 gives average costs of £1,800 for a mid-terrace rising to £4,600 for a detached house, with annual savings of £200 for a semi-detached gas-heated dwelling and a payback of around 9 to 12 years depending on property type³⁰. A trade body puts savings at up to £610 a year with a maximum of 5 years to repay, and states the measure lasts the lifetime of the property if the property is maintained; these figures are considerably higher than the independent estimates and the two sets are not reconciled³². Disruption for cavity wall work is rated low³¹. Reputable cavity wall insulation is said to come with a 25-year guarantee, either backed by the Cavity Insulation Guarantee Agency or an equivalent independent insurance-backed scheme³¹. Householders considering cavity fill are advised in Welsh government guidance to get advice from a qualified retrofit assessor before going further³³.

Applying after closure, and what remains

The application process has ended. The service to check eligibility for free or cheaper home insulation has closed, and installations had to be complete by 31 March 2026, when the scheme ended³. Local authority guidance confirms the scheme closed on Tuesday 31 March 2026, with applications having been made online via the GOV.UK portal, or through a participating home energy supplier¹⁶. Government guidance to suppliers refers to the ending of funding for both ECO4 and GBIS³⁴.

Where an application was already in train, the route was to contact the energy supplier applied to³. If eligible, the energy supplier arranged an assessment of the property; the household found out after the assessment whether any contribution was needed towards the installation, and could decide not to go ahead if they did not agree with the assessment or the costs³. A helpline operated on 0800 098 7950, Monday to Friday 8am to 6pm and Saturday 9am to 12pm³⁵. Ofgem's scheme enquiries address is GBIS.enquiry@ofgem.gov.uk, and contact details of obligated suppliers are published by Ofgem¹⁵.

Households still looking for insulation funding should look to the successor and parallel schemes rather than GBIS: the Warm Homes: Local Grant, ECO4 and VAT relief on energy-saving materials. A comparison of the closed scheme against its successor is at Warm Homes: Local Grant vs Great British Insulation Scheme, and closed schemes generally at closed home energy grants.

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

Insulation is the one household measure that reduces demand rather than shifting where energy comes from, and that makes it the foundation of any move towards self-sufficiency. A home with an insulated cavity needs less gas or electricity for the same comfort, permanently and without a control system, an app or a tariff to manage. Cavity wall insulation is stated to last the lifetime of the property if the property is maintained, which is a longer horizon than any heating appliance³². Where uninsulated cavities add up to 25 per cent to a heating bill, closing that gap reduces exposure to every future price movement²⁶.

The limits are real, and they are structural. GBIS was a single measure scheme: one insulation measure per home, with no minimum requirement for the property's SAP rating to improve⁴. A home with an uninsulated loft, uninsulated walls and a poor floor could only have one of those treated. That leaves most of the fabric untouched and the household still substantially dependent on the grid and on a gas supplier. Delivery of 126,000 measures against a 300,000-household forecast means most eligible homes were never reached⁶. And the scheme was itself supplier-funded: it was estimated to add £5 to a typical annual dual fuel bill in 2023/24 and £17 in each of the following two years, so the cost of the measures sat on everyone's bills, including those who received nothing⁷.

Dependence also persisted in the delivery chain. Whether work happened at all rested on an energy company's commercial decision about which retrofit projects to fund⁴. Redress rests with the installer's TrustMark guarantee rather than with Ofgem, which does not administer guarantees or financial protection and says its ability to resolve complaints is limited⁴. With reported quality issues on some solid wall insulation fitted through the scheme, the guarantee chain is the only protection a household holds³. Now that the scheme has closed, the fabric measure installed remains an asset; the funding route behind it does not. Further discussion sits on grants, schemes and household energy independence.