I heard once a actual math on the cost per degree of heat per square foot. I would imagine it is a rough formula of some sort, but I finally convinced my huisband to turn the heat down this year (last year we had just had our girl and I didn't try to hard) Anyway he was convinced because my SIL found out from the electric company that turning the air down 2 degrees made a 20% difference in the bill. Not sure how accurate that is but I used it to convince him to turn the heat to 67 degrees (which means when he is cold it will go up to 69
We have a new house so there is no issue with weather stripping or anything, just in getting the kids to get out the house faster so we can shut the door sooner!