I grew up in Northern Wisconsin (Ashland)
My Father was an electrician for the local paper mill up there. They provided plug-ins for the workers in the parking lot so their cars would start after sitting out all night (third shift)
As I recall, he said they had to put in several new circuits for all the block heaters. 500 to 600 amps worth at 120 volts!
The heaters available are oil pan, battery, coolant. The coolant heaters are the best.