My wife says every time I open the hangar door in winter it costs $50. A neighbor who offers winter storage actually charges $50 for each door opening. By the time spring arrives I won't care.
I suspect it depends on wind direction and OAT, but the $50 wouldn't be far off. In the winter (before departure) I run the hangar winch cable out to the door and I also leave a pair of ice overshoes by the door to accelerate the process of putting the plane back in. There's always a couple of times when it's windy and cold that nothing seems to go quick about getting the bird back in the nest....and then the heater runs for an hour or so to get everything back to temp.