It feels like very much a could country / could region distinction. In warmer regions of the world, heat pumps have been using for efficiently heating in winter

It feels like very much a could country / could region distinction. In warmer regions of the world, heat pumps have been using for efficiently heating in winter since the 1980s (that's as far as my memory goes). Of course, when the temperature rarely went below 0℃. If you look at the single-room AC units that now dominate these markets, you'll rarely find anything that cannot do both heating and cooling.