Page type: primary-anchored (mirrors Great British Insulation Scheme, ECO4A Order 2023, SI 2023/873)

Last updated: 2026-04-05

Great British Insulation Scheme (GBIS)

The Great British Insulation Scheme is a supplier obligation requiring licensed energy suppliers in Great Britain to deliver insulation and heating control measures to domestic properties. It runs from 25 July 2023 to 31 March 2026, targeting £55,998,000 in annual heating cost savings across all obligated suppliers (Art 3).

The scheme is formally the "ECO4A scheme," established by the Electricity and Gas (Energy Company Obligation) Order 2023 (SI 2023/873). It runs alongside the ECO4 scheme (SI 2022/875) with the same obligated suppliers but different eligibility rules and a deliberate single-measure design.

Source file: sources/desnz/gbis.md

How it works

Who is obligated

Any energy supplier that is an ECO4 participant under the 2022 Order is automatically a GBIS participant (Art 4(1)). Dual licence-holders (electricity + gas) count as two separate participants (Art 4(2)). The Administrator (Ofgem) determines each participant's share of the £55.998m target using a formula proportional to their customer base: D × (Tp/T), where D = £3.64m (Phase A) or £12.18m (Phases B and C) (Art 7(3)).

The three phases

The scheme divides into three phases, each with its own obligation allocation (Art 2(2)): - Phase A: 25 July 2023 to 31 March 2024 - Phase B: 1 April 2024 to 31 March 2025 - Phase C: 1 April 2025 to 31 March 2026

Participants must achieve at least 90% of each phase's obligation from measures completed within that phase (Art 9(3)). This creates a binding temporal delivery constraint. Backloading is penalised.

What measures qualify

A measure qualifies as an "ECO4A qualifying action" if it passes a six-condition gateway (Art 10):

1. General requirements (Art 11): must be an insulation or heating control measure, installed at domestic premises, reducing heating costs to 21°C/18°C, completed between 30 March 2023 and 1 April 2026, at premises built before 1 April 2022, with no public grant funding, and not already notified under ECO4.

2. One eligibility route from eight options:

3. Council tax band (Art 12): private premises in bands A-D (England) or A-E (Wales/Scotland), SAP band D-G, with tenure-specific exclusions
4. Help to heat group (Art 13): premises occupied by help to heat group member, SAP D-G
5. Social housing band D (Art 14): innovation measures only
6. Social housing bands E-G (Art 15): insulation measures (not heating controls)
7. Income declaration (Art 16): relevant authority certifies household income below £31,000, verified without self-declaration
8. Specified criteria (Art 17): SAP E-G, relevant authority confirms ≥2 criteria from ECO4 Order
9. Health referral (Art 18): health provider referral for person with cardiovascular, respiratory, immunosuppression, or mobility condition worsened by cold home

10. Debt/self-disconnection (Art 19): participant declares at SAP E-G premises with fuel poverty indicators

11. Additional requirements: pre- and post-installation RdSAP assessments for insulation (Art 22); smart meter advice (Art 22(1)(a)(ii)); heating controls must co-install with insulation within 3 months (Art 23)

12. Quality assurance: TrustMark-registered installer with lodgement certificate (Art 24)

13. Notification: written, after completion, within deadline (Art 25-26)

In-fill measures

The scheme allows extending insulation to neighbouring properties: - Flat in-fill (Art 20): solid/cavity wall insulation in the same block, linked to a primary qualifying measure, completed within 3 months - House in-fill (Art 21): solid wall insulation linked to 3 primary measures on the same street, within 3 months

Scoring

Each qualifying action receives a score: KM × (1 + IM + R) (Art 30), where: - KM = annual cost savings per Ofgem's published methodology (with 10% reduction) - IM = innovation uplift (0.25 standard, 0.45 substantial improvement) capped at 10% of low-income minimum (Art 31) - R = 0.2 for low-income off-gas rural Scotland/Wales measures; 0 otherwise

Smart thermostats scored using SAP 2023 Edition v10.2 (Art 32A, added August 2025).

Low-income sub-targets

Within the total obligation, participants must ensure: - 90% of each phase's low-income minimum requirement from low-income qualifying actions (Arts 13-19) (Art 9(5)) - At least 20% of the low-income minimum from "help to heat or social housing measures" (Arts 13-15) (Art 9(7))

Transfers and cross-scheme assignment

• Measure transfers (Art 33): joint application by both participants, by 30 June 2026
• Obligation transfers (Art 34): joint application before phase deadlines
• ECO4 reassignment (Art 34A, added August 2025): ECO4 delivery counts toward GBIS at 1.251× multiplier, capped at 75% of total GBIS obligation. This is the key relief valve for suppliers underperforming on GBIS.

Final determination

Ofgem scores qualifying actions between 1 July and 30 November 2026, determines compliance through a five-step calculation (Art A35), and notifies each participant of its final determination before 1 December 2026 (Art 35(1)). All participant requirements are enforceable by GEMA as "relevant requirements" under the Electricity Act 1989 and Gas Act 1986 (Art 38).

Key numbers

Defined terms

See source file defined terms register for the full list of 35 defined terms.

Cross-references

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