On 13/08/2020 13:24, Martin Brown wrote:


Do the sums very very carefully. It has to beat electricity since you
get the gain of the heat pump. It might beat bottled gas. But with
prices are as they stand now it might not beat oil or mains gas.


If you have a building (or part of a building) that needs aircon as well
as heat you can (perhaps) do it with one system. Perhaps you need a
better design of outdoor unit (vertical plates coated with PTFE, and an
auto defrost system that makes the ice fall off without needing much heat).

I think from time to time about adding a single system to one part of my
house where summer aircon would be nice and I can sometimes use a heat
boost in the winter to supplement the existing traditional gas/water
system. I think there is little doubt that in the long term we will be
going this way (although perhaps more with ground source heat pumps). I
guess one might build a hybrid system with an air HX for heat rejection
in the summer and a ground HX for winter heating.