Heat pumps are technically inverted A/Cs and can usually be put in inverted mode to act as regular A/Cs but they're often used to warm up / cool down water wher

Heat pumps are technically inverted A/Cs and can usually be put in inverted mode to act as regular A/Cs but they're often used to warm up / cool down water whereas a conventional A/C pumps the cooled air directly into the rooms. Heat pumps that work the same way are also sometimes called air-air heat pumps (contrasted with air-water, which in turn are contrasted with water heat pumps which pump brine into a network of underground pipes to create the heat differential). When picking a heating system my wife and I did look into air-air heat pumps but as we live in Central Europe and thus need the system for heating as much if not more than cooling and the building's insulation and rooftop solar panels already reduce the need for cooling outside very long and extreme heatwaves, we decided against it (and went with a more common air-water heat pump with underfloor heating) because they're not very efficient for heating. As I understand it, while underfloor heating retains heat at a stable level even when venting, airflow heating loses heat considerably more rapidly. To compensate, in order to heat up the room more rapidly, air-air heat pump systems often have electric heaters at the vents. These essentially work like an electric hair dryer and consume a lot of energy. On the other hand, underfloor heating is worse at cooling. Anecdotal reports seem to be mixed on both systems with the only consensus generally being that if you want either system to be more efficient you should look into insulation above all else.