In this paper the performance of a ground source heat pump (GSHP) system with horizontal coupled ground loop pipes was monitored, analysed, extrapolated and numerically simulated. The state-of-art facility of the Kortright Centre was used to experimentally monitor the performance of GSHP. The main objective was to develop cooling/heating performance curves based on the building loads and the source temperatures. In addition, it was aimed to evaluate the efficiency of the heat pump at different load/source temperatures and measure the cycling characteristics of the compressor. Furthermore, the heat pump was modelled using the performance curves obtained from the experimental investigation. TRNSYS was used to model the house as well as the heat pump. The model was validated using the daily thermal output and it was determined that the COP ranged from 3.05 (at an ELT of 44.4 degrees C and an EST of 2.7 degrees C) to 3.44 (at an ELT of 41.5 degrees C and an EST of 5.48 degrees C). The system was also investigated for potential improvements in the control strategies. The aim was to identify issues with the current controls of as installed system and determine methods for possible improvement in the overall efficiency. (c) 2015 Elsevier Ltd. All rights reserved.