If the temperature outside is -20, heat pumps have an efficiency of around 200%. That's nice. But if you feed it electricity from a coal plant running at 33% ef

If the temperature outside is -20, heat pumps have an efficiency of around 200%. That's nice. But if you feed it electricity from a coal plant running at 33% efficiency, total efficiency becomes 66%, less than many stoves. That doesn't take into account the transfer loss or the cost of producing an maintaining all that gear. In places where the vast majority of electricity comes from renewables or nuclear and where the supply is quite stable, heat pumps still make sense in cold weather. But using lignite based power plants to fuel heat pumps in Eastern Europe is something that is attractive more because it lets you heat buildings in highly populated areas while having the air pollution happen far away from population centers.