Pete C. wrote:
"Not@home" wrote:
....

My understanding is that heat pumps are more efficient, but need a
supplementary source of heat in areas where the winters are quite cold.

Air source heat pumps need supplemental (usually electric resistive)
heat in cold areas. Geothermal / ground source heat pumps don't since
their coils are below frost lines and soil temps are stable.

I'd revise that slightly as geothermal / ground source heat pumps _may_
not if sufficient heat source/sink capacity is available since
their coils are below frost lines and soil temps are relatively stable.

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