This study presents an integrated predictive model for the long-term performance assessment of ground source heat pump (GSHP) systems, which comprehensively considers the dynamic heat loads of the buildings and heat pump units (HPUs), the 3D dynamic heat transfer process in the ground heat exchangers (GHEs) and the energy consumption by the system accessories particularly the pumps. The model achieved significantly improved predictions than the conventional models and was in satisfactory agreement with the field-test data of an in-operation GSHP system, demonstrating the importance of systematic consideration of the dynamic system operational characteristics and 3D heat transfer processes in the GHEs. The model was also utilized to analyse the performance degradation of GSHP system induced by the soil thermal imbalance. It was found that increasing the thermal imbalance ratio of the accumulative building load from 35% to 76% led to a 10.7 degrees C further increase in GHE outlet water temperature, a half-folded cooling COP of the HPU and a shorter life-span. (C) 2017 Elsevier B.V. All rights reserved.