The build

The strange thing about Air source heat pumps is they are more efficient in the warm when you don’t want the heat, but are generally geared to be run at temps that are cooler than most of the UK, I think Scotland is ok, they come into their own in that zone around -5 to +5. Down south it’s not often we get those temperatures our winters are a lot milder.

Theoretically they can generate heat from extreme cold, as absolute zero is -273 degrees but, obviously the materials used in the operation would fail before getting there. They were being used as the heat source for the apartment we stayed in in lapland which was toasty, while the outside temp was -30 to -40 during the day. I didn’t measure it overnight but imagine by comparison it was cooler.