Establishing expected performance for residential air-to-water heat pumps under real-world conditions

As heat pumps become increasingly prevalent in residential buildings, discrepancies between expected and achieved efficiency can increase operating costs and undermine confidence in this technology. Yet, determining whether individual installations perform as expected remains challenging because efficiency strongly depends on operating conditions. Conventional assessments based on absolute efficiency thresholds cannot distinguish demanding operating conditions from additional performance shortfalls, while scalable methods for establishing installation-specific expectations are lacking. Here, we develop an approach to estimate expected heat pump efficiency under actual operating conditions, combining thermodynamic relationships, product-specific laboratory data, and field measurements. Validated using 176 heat pumps, the approach achieves a median absolute percentage error of 7.03%. Applying the method to 10,087 installations, we identify 5.1% with both low absolute efficiency and substantial deviations from expected performance. Systems falling below 80% of expected performance exhibit 2.3 times the incidence of subsequent recorded service contacts, whereas conventional absolute efficiency thresholds show no substantial difference between groups. These findings establish a scalable basis for assessing whether individual heat pumps perform as expected, enabling targeted performance monitoring and supporting greater transparency and efficiency in residential heating.