Oxford study proves heat pumps triumph over fossil fuels in the cold::Published Monday in the scientific journal Joule, the research found that heat pumps are two to three times more efficient than their oil and gas counterparts, specifically in temperatures ranging from 10 C to -20 C.
They’re spreading all over the Alps too. Easily a 50° temperature difference between summer and winter, and they tick over nicely for years with no problems
I think in Europe it’s a fairly common method now so reliability has been sorted out.
Generally the US is a decade or so behind everyone else though so it might take a while