Or even connect the cars to the electric mains at their house and heat them electrically.

See "Driving in winter" [1]

[1] https://finland.fi/life-society/how-to-survive-winter-in-fin...

Apparently in many new cars the electric heaters aren't good enough for colder climates, because these engines don't have factory options (or physical accomodation) for an electric heater that would heat the coolant - a lot of the heat is wasted to outside air and heating the engine exterior when the heater is tacked on the side of the engine. And they work with the same limited amount of power as the older ones.