An important consideration with regard to ground source heat pump (GSHP) systems is ensuring highenergy efficiency performance throughout the years. Multi-year analyses are thus exceedingly importantto evaluate the seasonal oscillations in the ground temperature and its long-term drift.

As only a limited number of results based on real cases are available in the literature, this work aims to address this paucity of information. Seasonal and long-term computer simulations were conductedin order to investigate the thermal performance of two office buildings in Italy with unbalanced load profiles.

The study focuses on the evaluation of ground temperature drift which was essentially due toan imbalance of the buildings’ load profile.An analysis, which was compared to two analytical approaches available in the literature, was carriedout using a detailed numerical model. The effects of improved load balancing of the ground load profileand of a higher number of boreholes on seasonal oscillations and on the thermal drift were investigated.The results showed that rebalancing the ratio between the heat extracted from and injected into theground led to better results from an energetic viewpoint almost certainly synonymous with an energetic-economic optimization.