ECO4 vs GBIS: What's the Difference and Why It Matters

Introduction

If you have had a call offering "free government insulation", it was probably about ECO4 or the Great British Insulation Scheme (GBIS). Both were funded by energy suppliers and administered by Ofgem, but they had different rules. Official audits later found serious problems with wall insulation fitted under both. GBIS has now closed and ECO4 ends on 31 December 2026.

What is ECO4?

ECO4 (Energy Company Obligation 4) is the fourth round of a scheme requiring medium and large energy suppliers to fund energy efficiency improvements, aimed at low-income households in homes with poor energy efficiency ratings.

ECO4 Key Features

• Duration: April 2022 to 31 December 2026 (extended, and now winding down)
• Homes upgraded to March 2025: 243,900
• Focus: low-income households, often with several measures in one home
• Measures: insulation, including external, internal, cavity wall and loft insulation, and heating upgrades such as replacing or repairing a boiler
• Funding: paid for by energy suppliers and recovered through energy bills

ECO4 Eligibility

gov.uk says you may qualify if you live in private housing and claim one of these benefits:

• Universal Credit
• Pension Guarantee Credit or Pension Savings Credit
• Income Support, income-based Jobseeker's Allowance or income-related Employment and Support Allowance
• Child Benefit or Housing Benefit

Your home's energy rating must be D to G if you own it, or E to G if you rent privately. Social housing rated E to G can also qualify, and some councils refer other households. There is no central application: contact your council or an energy supplier. Availability depends on suppliers, and work must be finished by 31 December 2026.

What is GBIS?

The Great British Insulation Scheme, formerly known as ECO+, began in April 2023 and closed on 31 March 2026 with no extension.

GBIS Key Features

• Duration: April 2023 to 31 March 2026, when it closed
• Homes upgraded to March 2025: 60,600
• Focus: wider eligibility than ECO4
• Measures: mostly single insulation measures such as cavity wall and loft insulation, but also some external and internal wall insulation
• Funding: also paid for by energy suppliers

GBIS Eligibility (When It Was Open)

Ofgem describes two groups:

• Low-income and vulnerable households
• Homes with an EPC rating of D to G in Council Tax bands A to D (England) or A to E (Scotland and Wales)

Side-by-Side Comparison

The Problem: Both Schemes Shared the Same Flaws

The Public Accounts Committee found the same weaknesses ran through both schemes:

1. A Complicated System

The schemes and the quality assurance system behind them were "too layered, fragmented and complicated", with unclear responsibilities. The department accepted there were serious failings at every level.

2. Checks That Were Not Independent

When the Committee reported in January 2026, there was still no requirement for the retrofit coordinator, who checks the work, to be independent of the installer.

3. A Complex Supply Chain and Fraud Risk

Ofgem told the Committee the supply chain is very complex. Ofgem estimated that falsified claims may have been made on 5,600 to 16,500 homes, and no single organisation was responsible for proactively looking for fraud.

4. Vulnerable Homeowners

The Committee said schemes designed to reduce fuel poverty "have instead left some of the most disadvantaged households living in cold, damp or unsafe conditions".

Why External Wall Insulation Failed So Often

The audits found that 92% of homes with external wall insulation had issues affecting its performance, often creating a risk of water ingress and mould, and 6% had health and safety risks such as inadequate ventilation. External wall insulation is a whole system, and common weak points include:

• Detailing: around windows, doors, the roofline, pipes and ground level
• Existing problems: damp or defects in the wall not dealt with first
• Ventilation: not enough ventilation once the home is better sealed
• Assessment: the whole home not properly assessed before work

GBIS Problems

GBIS mostly funded cavity wall and loft insulation, but its external and internal wall insulation is covered by the same audit findings. Other measures can also go wrong:

Cavity Wall Insulation Problems

• Installed in walls that were not suitable for it
• Used on walls exposed to driving rain
• Incomplete fills leaving cold spots
• Rain crossing the cavity where the outer wall is in poor repair

Loft Insulation Issues

• Eaves ventilation blocked, leading to condensation in the roof space
• Electrical cables or fittings buried under insulation
• Existing roof defects not reported before the work

Does It Matter Which Scheme Funded Your Work?

For getting faulty work put right, the routes are the same under both schemes. What matters is the type of insulation:

• External wall insulation: TrustMark's free Find & Fix audit, on 0333 555 1234 (option 1). See our guide to the free audit.
• Internal wall insulation: Ofgem's ECO contact centre, on 0808 169 4447 or ECOhelp@ofgem.gov.uk.
• Other measures: the installer, then its TrustMark Scheme Provider, then the Dispute Resolution Ombudsman. For cavity wall insulation, also check your guarantee (often CIGA or the Installation Assurance Authority).

If you do not know who installed your insulation, you can send Ofgem a subject access request at ECO.SAR@ofgem.gov.uk with two proofs of address. For a missing guarantee on work after 1 January 2020, email TrustMark at info@trustmark.org.uk.

Red Flags

Whatever the scheme, watch for these warning signs:

• High-pressure sales tactics: "Offer ends today" or "Limited availability"
• No proper assessment: the whole home should be assessed before work starts
• Vague company details: no company registration number or TrustMark registration you can check
• Fees for free routes: anyone charging you to access the free Find & Fix audit or to handle a "claim"
• Rushed timeline: pressure to start work within days of first contact
• No reference number: a caller about the audit who cannot quote your Unique Measure Reference Number

What You Should Do

Before Any New Installation

1. Check the company on TrustMark's register
2. For paid work, get more than one quote
3. Ask for a whole-home retrofit assessment, and consider independent advice before wall insulation
4. Ask about recent local jobs and speak to those households if you can
5. Check Companies House for how long the company has traded
6. Ask which provider will guarantee the work, and get the details in writing

After Installation

1. Keep the handover paperwork, guarantee certificate and any Ofgem letter
2. Take dated photos
3. Keep all correspondence
4. Report problems through the route for your insulation type (above)
5. Watch for warning signs: damp, condensation, cracking

Future of the Schemes

• GBIS: closed on 31 March 2026 with no extension
• ECO4: ends on 31 December 2026, with no successor supplier obligation planned
• Warm Homes Plan: published on 21 January 2026, setting out future government support, including Warm Homes: Local Grant run by councils in England
• Consumer protection: a consultation on reforms closed on 10 September 2026, with changes targeted for around summer 2028
• Repairs: TrustMark's Find & Fix programme is intended to finish by May 2027

Get Advice

If you are worried about work already done, use the free routes above first. The Citizens Advice consumer helpline (0808 223 1133) can also help.

Related Articles

• Complete Guide to ECO4 Scheme Problems
• Great British Insulation Scheme Problems
• External Wall Insulation Issues & Solutions
• The NAO Insulation Report: Complete Analysis

Sources

• gov.uk — Energy Company Obligation
• gov.uk — Extending the ECO4 end date: government response
• Ofgem — Great British Insulation Scheme
• National Audit Office — Energy efficiency installations under the Energy Company Obligation (HC 1334, 14 October 2025)
• Public Accounts Committee — Faulty energy efficiency installations (HC 1229, 23 January 2026)
• Ofgem — ECO complaints process
• gov.uk — Warm Homes Plan
• gov.uk — Reforming consumer protection for home upgrade schemes