I guess this post was meant just for me :D . We have a very small house about 900 square feet and our bill has been climbing and climbing since the heat wave hit. We received our bill today at almost 500 bucks YIKES! No, we don't have it set at 40 either. Today the fan wasn't blowing anything, called the landlord and the repair guys called and said that it was probably 'frozen'. So we turned it off the past hour or so and it started blowing a little, then I read this post..... Yep, there are batteries in the silly thermostat! Let's see if that makes a difference and THANK YOU for posting this!