Bridging the efficiency divide: open-source insights into UK heat pump performance gaps

Abstract

This study utilises real-world data from the open-source HeatPumpMonitor.org platform and the UK's Electrification of Heat trial to investigate the significant gap between the expected and actual performance of heat pumps. Analysis of systems with an average seasonal performance factor (SPF) of 3.8 from HeatPumpMonitor.org shows that high efficiency is strongly correlated with operation at low flow temperatures, specifically an average of 34 °C. In contrast, the Electrification of Heat trial reported a lower average SPF of 2.81, which is more representative of the wider market. The paper identifies several key factors contributing to this performance gap, including sub-optimal weather compensation settings that lead to unnecessarily high flow temperatures, cycling on room temperature and a high proportion of time spent at less efficient compressor operating points such as high modulation. Other factors include significant oversizing of heat pump units, large temperature setbacks, and issues with domestic hot water controls. The findings provide clear technical and policy recommendations to optimise heat pump performance. These include designing systems for low flow temperatures (≤40 °C), performing accurate heat loss calculations to prevent oversizing, and ensuring careful commissioning. The paper concludes that closing the performance gap can be achieved through a combination of best-practice design, improved installer training, and policy frameworks that encourage high real-world performance.