A techno-economic comparison of a direct expansion ground-source and an air-source heat pump system in Canadian cold climates

• A techno-economic comparison between DX-GSHP and ASHP is undertaken.
• A detailed numerical modeling of both systems is performed.
• The effect of heat pump capacity and borehole size on system costs is evaluated.
• Under good design condition, DX-GSHPs offer some performance and cost advantages over ASHPs.

This study aims to compare two commonly used ASHP (air-source heat pump) and DX-GSHP (direct-expansion ground-source heat pump). There have been many debates on energy efficiency, system costs and relative payback period of DX-GSHP against ASHP systems over the past few years. In this context, and with the aim of enriching this debate, a detailed screening heat pump model previously developed is modified and used to compare the seasonal performance of ASHP vs DX-GSHP in a residential building in the cold climate city of Montreal. Further, a life cycle cost analysis is performed to account for the difference between initial and 10-year operating costs of the two systems based on the current prices in Quebec. The obtained results show that by proper sizing, energy consumption of the DX-GSHP system can be reduced by 50%. Moreover, with current borehole installation prices, the relative payback period of the GSHP (ground source heat pump) compared to ASHP is more than 15 years. However, if the borehole installation price reduced by 50% the payback period would be reduced to just a few years. Such results highlight the importance of further investigations in the area of DX-GSHPs, in order to reduce the borehole installation cost and increase its performance.