[occz]

Gas is still an inferior solution in those cases - wood pellets are better for those climates. Better yet, a combination of heat pumps and wood pellet furnaces gives you the best of both worlds - very energy-efficient heating while the temperature is still not too far below freezing (iirc heat pumps still beat alternatives as far down as negative 10-15 C), and wood pellets to handle the most extreme colds of the year.

There's also the alternative of putting the outlet of the heat pump below ground, where the temperature never gets that far below zero.

It's entirely incorrect to say that heat pumps only work in mild climates. I live in a country where we do not have a mild climate, and heat pumps are becoming more popular each day, owing to their technological superiority.