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The National Audit Office (NAO) has been analysing progress since the government published its Heat and Buildings Strategy in October 2021. The strategy set out an ambition to end the installation of new fossil fuel boilers by 2035 and grow the supply chain for heat pumps to a minimum market capacity of 600,000 installations per year by 2028.
By 2035, government wants to see up to 1.6 million heat pumps being installed annually.
According to today’s NAO report, Decarbonising Home Heating, there were 55,000 heat pump sales in 2022.
The government’s flagship Boiler Upgrade Scheme has also underperformed, installing just 18,900 heat pumps between May 2022 and December 2023. The Department for Energy Security & Net Zero (DESNZ) had expected the scheme would have delivered 50,000 installations by this point.
The NAO says the government’s assumptions about levels of consumer demand and manufacturer supply are optimistic.
A key issue behind lower-than-expected heat pump uptake is their cost to use and install, the NAO says. DESNZ delayed its planned work to reduce running costs, by rebalancing gas and electricity prices, for example by moving some levies and charges from electricity to gas bills. The department says that price rebalancing remains an essential policy but is challenging. Heat pump installation costs also fell more slowly than DESNZ hoped.
The NAO also found that DESNZ has no long-term plan to address the low levels of awareness among households about the steps required to decarbonise home heating.
In response to the Boiler Upgrade Scheme’s underperformance, DESNZ increased the grant available to people replacing boilers from £5,000–£6,000 to £7,500, which has enabled some energy suppliers to offer heat pump installations starting at £500. Applications to the scheme in January 2024 increased by nearly 40% compared with January 2023, though more data is required to determine whether the change is sustained.
DESNZ is also considering what role hydrogen will play in decarbonising home heating, despite the National Infrastructure Commission telling it to forget about hydrogen. The department has so far indicated that it will have a limited role but it will formally take a decision in 2026.
Trials of hydrogen schemes intended to provide evidence to support the government’s decisions have been delayed or cancelled. Stakeholders told the NAO ongoing uncertainty could slow progress by limiting the ability of local authorities and industry to plan and invest.
Parts of the gas network may need to be decommissioned if natural gas is no longer in use and hydrogen is confined to certain areas of the country. DESNZ is working to develop its understanding of the consequences for gas networks of decarbonising home heating and how decommissioning could be funded.
The NAO recommends government considers providing more certainty on the role of hydrogen in home heating before 2026.
To improve its transparency and accountability on the rollout of heat pumps, the NAO says government should report progress annually to Parliament.
Gareth Davies, the head of the NAO, said: “Government needs to engage every household to achieve its objective to decarbonise home heating as part of the transition to net zero. DESNZ’s progress in making households aware and encouraging them to switch to low-carbon alternatives has been slower than expected.
“DESNZ must draw on its experience to date to ensure its mix of incentives, engagement and regulations addresses the barriers to progress in its current programme of work.”
Philip Dunne MP, chair of the House of Commons environmental audit committee, said: “The NAO’s latest report is a timely reminder of the challenges that remain in improving the energy performance of our homes. While the government is making progress towards decarbonising homes through insulation schemes, more remains to be done. Decarbonising older and less efficient homes will be more difficult, but it is an unavoidable part of the net zero transition.
“Rapid adoption of innovative technologies like heat pumps can play a bigger role in moving these harder to insulate homes away from fossil fuel heat. But successfully installing heat pumps often requires significant additional work. The now disbanded Energy Efficiency Taskforce was expected to propose innovative ways to make installations and retrofits more affordable; improving affordability must remain top of the agenda.
“The committee knows that decarbonising our housing stock is a central part of the journey to net zero. Throughout this parliament, we have sought to point the government in the right direction, and returned to examine this topic frequently. We are likely to do so again before the next election, and I look forward to conducting further scrutiny on the government’s plans.”
The National Audit Office report, Decarbonising home heating, is available at www.nao.org.uk/reports/decarbonising-home-heating
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