We live in the Colorado Front Range in a 50 year old house that isn't particularly well insulated. We have a Mitsubishi high-efficiency air source heat pump dis

We live in the Colorado Front Range in a 50 year old house that isn't particularly well insulated. We have a Mitsubishi high-efficiency air source heat pump distributing air through our existing duct work. We have electric backup inside the air handler. Last week it got down to -15F overnight. The heat pump ran throughout and there was only really activity from the electric backup during the occasional defrost cycle. We keep our house pretty warm too as we have a baby. In winter the heat pump seems to have no issues meeting our heating needs albeit at quite a bit higher overall utility cost compared to our old gas furnace. In summer the heat pump is much more efficient than our old AC unit and our solar panels cover >100% of our usage from ~April-Oct. Prior to installing the heat pump we did as much insulating as we could (mostly attic) and I think that was important for enabling the heat pump to keep up in the cold. The nature of the heating is lower level and continuous compared to the occasional blasting from a gas furnace, so you do want to prevent rapid leakage of heat from the house.