I used to be an energy waster.  Guilty as charged.  When I was in the military, I lived in government housing on base and they paid for everything: electricity, water, housing upkeep, etc, etc.  So I'd leave my AC on 68 all the time, no matter if I was there or not.  In fact, I wouldn't even shut off my TV or any of the lights before I left the house.  Now since I'm out of the military and paying for it, I'm a lot thriftier.