“Performance gaps and quality assurance challenges in the UK heat pump roll-out: evidence from 1,700 metered installations”
This paper presents a comprehensive analysis of in-situ performance data from 1,700 domestic heat pump installations carried out under the UK’s Renewable Heat Incentive (RHI) between 2017 and 2022. The dataset – obtained by UK’s Department for Energy Security and Net Zero (DESNZ) – includes approximately 300 ground-source systems, providing a unique large-scale insight into ground source heat pump (GSHP) performance. The analysis compares measured Seasonal Performance Factors (SPF) with installer design forecasts based on the Seasonal Coefficient of Performance (SCOP) metric. Although a substantial proportion of heat pumps met the SPF = 3.0 benchmark (30% of ASHPs and 67% of GSHPs), median SPFs fell notably short of installer design forecasts: 2.69 for ASHPs (design SCOP 3.59) and 3.26 for GSHPs (design SCOP 3.93), representing performance gaps of 0.97 and 0.70 respectively. The correlation between measured and forecast efficiencies was weak (Pearson r = 0.225 for ASHPs; r = 0.228 for GSHPs). These findings closely align with results from the independent Electrification of Heat (EoH) Demonstration Project, which reported a comparable performance gap (ASHP SPFH4 difference = 0.85), validating both studies. Further analysis of the dataset from the EoH project is described in this paper. The study finds that although heat-pump technology is reliable, many installations underperform, risking consumer trust and hindering UK decarbonisation. It recommends evolving regulations to focus on outcomebased assurance – such as public performance databases, post-installation monitoring incentives and the establishment of minimum in-situ performance thresholds (e.g. SPF = 2.5) or contractual guarantees assigning outcome responsibility to installers. These strategies aim to de-risk the market for consumers, discourage "fit-and-forget" installation practices and ensure transparency. They also reflect the principles of regulatory science, emphasising evidence-based, adaptive policymaking informed by measured real-world outcomes. Building trust and reducing financial risk are crucial for broader heat pump adoption over gas boilers.