> Heat pumps and air conditioners are identical, with the sole difference being that the heat pump can _also_ function as a heater/furnace. That's a pretty hug

> Heat pumps and air conditioners are identical, with the sole difference being that the heat pump can _also_ function as a heater/furnace. That's a pretty huge difference from the user's point of view. Take an existing house that does not have cooling, and has either fossil fuel heating or electrical resistance heating. The owners want to add cooling. If they get an AC for that then later decide they want more efficient heating in winter the cost of doing that (whether by getting a new efficient heating system or by making the modifications necessary to add heating mode to their AC) are likely to be quite a bit more than than the extra it would have cost to get a heat pump instead of an AC when they were just trying to add cooling.