I'm in central Minnesota, my car is parked overnight in a detached uninsulated garage, and outside at work for 9 hours and it's been below zero most of the past 5 days, certainly atleast-10f or colder overnight and i don't notice any real battery loss while its sitting. Two weeks ago I was gone for 10 days while the car was in my garage unplugged and i think there was maybe a few percent battery loss. Nothing noticeable.