Heat pump water heaters are not the same thing as heat pumps used for home heating. Please edit your comment to make it clear you misunderstood what I was talking about.

My expectation is that an air source heat pump would not work well here, at considerably higher cost than the gas furnace when installing is included in the comparison. Air source probably not working well is why I talked about drilling (each paragraph is a topic; water heating in the first and home heating in the second...).