[socks]

You just helped me realise (as an Aussie living in Europe) that when some people are saying "air-to-air heat pump" what they mean is what an Aussie or Kiwi would call "reverse cycle air conditioner" - which are extremely common and affordable. The heat pumps I have seen personally in Europe are geothermal, very big, and very expensive.

[bkor]

> The heat pumps I have seen personally in Europe are geothermal, very big, and very expensive.

In NL I saw loads of water/water heat pumps (so using geothermal) in plans for new buildings. The latest plans now seem to prefer air/water. The air/water is cheaper and the units nowadays are much quieter than they used to be. This is just my observations, I could be way off.

[ianleighton]

I think your reverse cycle ac would be an air-to-air heat pump. Air-to-water is more like your heat pump water heater, with the hot water then going through radiators.