I am in Wisconsin to. And to be honest I would never think of heating my coop. These birds have been here long before us and I think it throws them off. If your coop is tight as mine is. I have 11 birds in a 6 x 8 coop and a thermostat in there. I have gone out in the mornings when is in the negatives and their coop is comfortably in the 20s with no heat. They then pop out to their run which is covered with plastic like solar heater and there are bails of straw to block the north winds and they are happy as can be.
I love my birds as much as everyone else but thing we tend to get carried away at time.
By the way Happy Holidays everyone