[fancyfredbot]

Air to water heat pumps are typically less efficient than air to air. Both will work in cold UK temperatures. However the water is often heated to a higher temperature which can reduce efficiency.

[msh]

That seems to not hold up when checking. Fx according to https://daikinquebec.net/en/heat-pump/air-vs-water-vs-geothe...

Air2air have a cop of 2.5 - 3.2 while air2water it’s 3.0 to 3.5