Boiler Upgrade Scheme

Infrastructure and Construction

Record date: 31 March 2026

Whole-life cost: £3.1bn
Published schedule: Not disclosed – 31/03/2030
NISTA delivery confidence: Not disclosed
Senior responsible owner: Not disclosed

What the project is for

The Boiler Upgrade Scheme (BUS) is part of a wider package of measures to drive significant heat pump deployment and support the expansion of the low carbon heat market. The scheme provides grants to encourage property owners to replace existing fossil fuel heating with more efficient, low carbon heating systems including air source heat pumps (ASHP), ground source heat pumps (GSHP) and, in limited circumstances, biomass boilers. The grant available for an ASHP and GSHP is £7,500, and £5,000for biomass boilers. The scheme was set to run from April 2022 until March 2025 supported by £450m. The scheme has been extended to 2029/30 and the funding allocation for 2025/26 to 2029/30 is £2,687m as set out in the Warm Homes Plan.

Departmental delivery commentary

The SRO delivery confidence assessment rating for 25/26 remained at Amber. The scheme is operationally mature and performing strongly, with sustained year‑on‑year growth in deployment. Applications in 2025/26 were up 19% on 24/25, with redemptions up 21%. The BUS Evaluation evidenced a high level of property owner satisfaction at 91% and MCS outreach recorded an average 95% satisfaction rate. The implementation of scheme changes announced in the November 2025 Government Response, will improve access, stimulate demand and strengthen consumer protection, and come into force from 28 April 2026. The Full Business Case for FY 2026/27 to 2029/30 has received TAP approval, confirming funding for the remainder of the scheme timeline. While demand and delivery continue to grow, overall delivery confidence remains dependent on wider market and policy factors, including the delivery of the Warm Homes Plan; given the materiality of these dependencies, an Amber rating remains appropriate.

Schedule

The project end date in 2025/26 was extended from March 2026 to March 2030. This reflects the extension of the scheme following the Spending Review, which provided additional funding and extended delivery to March 2030.

Cost

The project’s departmentally agreed whole life cost increased due to the extension of the scheme to 2030 following the Spending Review, which increased both the duration and scale of delivery. As a result, total funding for the extension period increased with the annual budgets set out in the Warm Homes Plan in January 2026.

Benefits

The project’s departmentally agreed benefits at Q4 2025/26 are estimated at £4,043m (real prices, base year 24/25). These benefits primarily reflect the monetised social value of carbon emissions reductions and air quality improvements arising from the installation of low-carbon heating systems under the scheme. These benefits are partially offset by disbenefits, reflecting the additional capital and maintenance costs associated with these technologies, as well as long run variable costs of fuel, relative to a like for like replacement of incumbent heating systems, which are typically fossil fuel boilers.