Elsewhere in this thread fastbeef says "They're very common in Sweden and can easily warm an entire house even at -20 C [-4F]." So, it can work though at -10F you would probably need supplemental heat.

Of course in Sweden residential natural gas prices are almost 4 times what they are in the US so its a very different economic decision. Shows what a carbon tax can do.

https://www.statista.com/statistics/702735/household-natural...