Heat pumps are a critical technology in decarbonising residential heating in the UK. The UK government set out its market-based approach to increasing the deployment in October 2021. Since then war has broken out in Europe, contributing to a global energy crises and the rise of domestic energy prices in the UK, Prime Minister Boris was replaced by Liz Truss and then Rishi Sunak, the UK economy experienced a period of sharp inflationary pressure causing a wider 'cost of living crises'. Given these disruptive events, the project examines how the UK market for residential heat pumps has developed in recent years, up until May 2023, and considers what is now required to accelerate heat pump deployment in the UK. The research proceeded in three phases. In phase 1 a literature review was undertaken followed by eight scoping interviews with policy makers, academics, and industry. The interviews were undertaken to build understanding of heat pump deployment from a socio-technical, whole systems perspective and gather insights about important elements of the system that may have changed given recent events. In phase 2 In Phase 2 a rapid review of the UK market for heat pumps was undertaken. Results of phase 2 were then feed into three stakeholder workshops, where participants were presented with new information before being guided through a series of exercises which culminated in participants collectively making decisions about what steps should now be taken to accelerate heat pump deployment in the UK. The workshops resulted in a rich set of data for analysis, including both written statements and audio transcripts. Analysis of both elements concentrated on areas of agreement, tension, and trade-offs made in reaching prioritised change solutions. The data consists of eight open-ended interviews from across policy, business, and academia. The interviews were undertaken to develop a socio-technical, whole systems understanding about the diffusion of residential heat pumps in the UK and gather insights about what system elements might have changed in recent years. The interviews were conducted in March 2023, lasted between 30 and 120 minutes and were guided by the question: "How have the multiple crises experienced across 2022 impacted the UK market for residential heat pumps in your opinion?".

Interviewees were sampled for diversity, selected for the their knowledge of and participation in the diffusion of residential heat pumps in the UK. Potential interviewees were contacted via email by the primary researcher. Interviews were conducted via Microsoft Teams and lasted between 30 and 120 minutes depending on how much time the interviewees were will provide and on their propensity to talk.