I live in Wisconsin where it can get down to -20 before wind-chill in the winter and the heat index pushes 100 in the summer, plus our summers are basically always 100% humidity for months at a time. My house was built before the turn of the century (the 19th century specifically) and both my furnace and AC are on their last legs. With all that said, I get $250 bills in the summer months and it pushes close to that in the winter, but during the spring and fall when it's a lot more reasonable they can get under $100