This paper presents an overview of the International Energy Agency (IEA) technology collaboration program Heat Pumping Technologies (HPT) Annex 52, "Long term performance measurement of ground source heat pump (GSHP) systems serving commercial, institutional and multi-family buildings." This project, which ran from 2018 through 2021, focused on measuring the performance of larger GSHP systems, going beyond energy use intensities which commingle the performance of the building envelope, occupancy effects and the system performance. Instead, performance factors were calculated, similar to coefficients of performance, but measured over various time intervals and system boundaries. The primary objectives of the Annex were refining and extending methodologies to better characterize system performance in larger buildings, creating a library of quality long-term measurements in the form of case studies, and providing guidelines for instrumentation, uncertainty analysis, key performance indicators, data management and quality assurance.

This paper summarizes the Annex outcome and illustrates use of the Annex boundary levels with a comparison between typical European and US GSHP systems. It is anticipated that this experience and the guidelines produced as a result of this experience will lower the cost and improve consistency and quality for future performance measurements.