The objective of this paper is to examine the impact of climate change on the energy performance of a typical residential ground-source heat pump (GSHP) system equipped with a horizontal ground heat exchanger (GHE) and located in a heating dominated climate (Montreal, Canada). Simulations results under future weather conditions (Relative Concentration Pathway – RCP8.5) show a drop in heating and a rise in cooling energy loads over 30 years. The outlet temperature from the GHE increases consistently from year to year and shows a high degree of variability in-line with the general trend of future ambient temperature fluctuations. In terms of electricity consumption, the main conclusion is that the use of current TMY weather files is inadequate to predict the yearly electricity consumption fluctuations.