The trouble with water heaters is you want hot water year round. Heat pumps are pretty ineffective once you get down close to freezing. So having an exterior ai

The trouble with water heaters is you want hot water year round. Heat pumps are pretty ineffective once you get down close to freezing. So having an exterior air source heat pump would only make sense for maybe half the year in a lot of locations. Generally utility rooms in houses have a decent amount of waste heat anyway from being near the furnace, so it probably does work out decently a lot of the time. My in-laws have a heat pump water heater and it makes their basement noticeably colder in the summer, which is pretty nice.