Ofgem published the Great British Insulation Scheme Delivery Guidance V1.0 on 31 August 2023, setting out how it will administer the scheme and how energy suppliers must deliver energy efficiency measures to domestic premises1. The scheme was established by the Electricity and Gas (Energy Company Obligation) Order 2023, known as the ECO4A Order, which was made on 24 July 2023, with parts 1 to 9 of the legislation coming into force the following day, 25 July 20231.
The guidance states that energy suppliers must achieve a total of £55,998.0002 in notional annual bill savings over the three years of the scheme, to be achieved no later than 31 March 20261. That total is split into three phases:
| Phase | Period | Target |
|---|---|---|
| Phase A | 25 July 2023 to 31 March 2024 | £7,280,0009 |
| Phase B | 1 April 2024 to 31 March 2025 | £24,359,000 |
| Phase C | 1 April 2025 to 31 March 2026 | £24,359,000 |
Suppliers must meet at least 90% of their Phase A and Phase B targets through measures completed before the end of each phase, and will be able to transfer measures until 30 June 20261. All measures under the scheme must be completed after 30 March 2023 and on or before 31 March 2026, with anything delivered from 30 March 2023 until 24 July 2023 classed as early delivery measures1.
On eligibility, the guidance describes two groups. The general group can receive measures if they live in a home in Council Tax bands A to D in England, A to E in Scotland and A to E in Wales, with a SAP rating of D and below1. The low-income group mirrors the Help to Heat Group criteria under ECO4, focusing on SAP rated properties D, E, F and G with low-income and vulnerable households1. The guidance also states that a supplier cannot partially or wholly fund a measure with funding from other government schemes or grants, whether from local, devolved or national government1.
"The Great British Insulation Scheme which will run from 25 July 2023 (the date of commencement of the relevant parts of the ECO4A Order) until 31 March 2026"
A later Ofgem summary of updates records that V1.0 was published on 1 September 2023, while the same document gives its publication date as 31 August 20232. The summary also records that the GBIS Measures Table V1.0 was published on 7 August 2023, and that a draft delivery guidance V0.1 was published on 30 May 20232.
Why it matters for households
The guidance sets the rules that determine whether insulation installed in a home can count towards a supplier's obligation, and therefore whether it can be funded through the scheme at all. The completion window, running from 30 March 2023 to 31 March 2026, and the Council Tax band and SAP rating conditions define which homes fall inside the Great British Insulation Scheme1. The ban on combining scheme funding with other government grants affects how a retrofit is put together where more than one source of support is involved1. For a household, the practical effect is that the scheme's contribution to insulation and energy independence depends on the property meeting the band and rating tests, and on the measure being completed inside the scheme dates.
What happens next
The guidance states that suppliers will be able to transfer measures until 30 June 20261. Ofgem's later summary records that it was working on a process to allow manual notification before 31 January 2024 should the register not be available to accept notifications2. No further dated steps are given in the published guidance.