I live some 5 hours north of Montreal, we have few days at -40C and wall radiators (not sure about the name) are needed, but for most of the winter days we use the heat pump to heat the house (-21C and up). Some members in my family work in AC/Refrigeration industry and all of them have thermo pumps, which make economic and ecologic sense. On the other side I don't know about AC/heat pump replacements as it's not common to have AC for the just a handful of days that could be very hot.