Ground-source real-world cost effectiveness for residential use isn't that great (see here, although unfortunately paywalled: https://www.greenbuildingadvisor.c

Ground-source real-world cost effectiveness for residential use isn't that great (see here, although unfortunately paywalled: https://www.greenbuildingadvisor.com/article/geothermal-heat-pumps-reputation-vs-reality https://www.greenbuildingadvisor.com/article/geothermal-heat...). The gotchas are the energy used to run the circulator for the ground loop, and the fact that over the course of a heating or cooling season the ground temperature lowers or raises, respectively, by enough that the COP isn't even much greater than an air-source system (but this would definitely vary by climate). Coupled with the much higher installation cost, it's a bit hard to make a system pencil out for a building the size of a single-family house.