Ofgem has added scores for smart thermostat measures to the Great British Insulation Scheme scores matrix, in an update dated 22 April 2025 and labelled Version 31. The matrix sets out the scores energy companies receive for measures installed under the scheme1. Smart thermostats are the first heating control measure to appear in the matrix, which previously covered insulation measures only.
The scheme adopts the ECO4 partial project scores framework, so the matrix is identical to the ECO4 partial project score matrix, with the exception of ineligible measure types being removed1. The matrix was originally published on 30 May 2023 as Version 11. Version 2, dated 20 July 2023, added Hybrid Wall Insulation (HWI) measure types1.
A further update applies to Version 3 and is dated 06 August 20251. It sets out which products can be notified as a smart thermostat. Where the pre-retrofit RdSAP assessment uses RdSAP 10, a product can only be notified as a smart thermostat where it is listed in the SAP 10 PCDB as a smart thermostat, for use with the heat source of the home where it is installed1. Ofgem states that the PCDB currently lists smart thermostat products only for the following pre-main heat sources1:
| Pre-main heat source |
|---|
| Condensing Gas Boiler |
| Non-Condensing Gas Boiler |
| Condensing LPG Boiler |
| Non-Condensing Liquified Petroleum Gas (LPG) Boiler |
Whether a product is eligible to be notified as a smart thermostat depends on the version of RdSAP used in the pre-retrofit assessment, and Ofgem directs readers to the section on Smart Thermostats within Chapter 5 of the GBIS Delivery Guidance for more detail1. The scores matrix itself is published as a spreadsheet, with Version 3 available as an XLSX file and Version 2 as a CSV1. The scores attached to smart thermostat measures, and the rates payable, have not been reported in the published guidance page.
"Scores for Smart Thermostat measures have been added to the matrix."
Why it matters for households
The Great British Insulation Scheme works through energy companies, which receive scores for measures they install. Adding smart thermostats to the matrix means a heating control now sits alongside insulation in the same scoring framework, rather than being outside it. For a household, a heating control affects how existing heat is used rather than how much heat escapes, so it addresses a different part of a home's energy independence: the running cost and the timing of heating, not the fabric of the building.
The eligibility wording ties notification to the SAP 10 PCDB and to the heat source of the home where the product is installed1. The listed pre-main heat sources are gas and LPG boilers, condensing and non-condensing1. Homes heated by other sources are not covered by that list as published. Households weighing a control against insulation measures, or against the Warm Homes: Local Grant, may find the comparison with ECO4 relevant, since the two matrices are otherwise the same1. The difference between a smart thermostat and a traditional programmer, and between smart TRVs and a smart thermostat, is not addressed in the scoring page.
What happens next
The Version 3 update is dated 22 April 2025 and the further update applicable to Version 3 is dated 06 August 20251. No further version or date has been reported.