I am living with 3 other girls in a house for the next year. None of these girls have ever had to pay any bills (they lived in dorms). I, on the other hand, have lived on my own and am used to paying bills. I have already noticed the annoying habit of them leaving the lights on while they are not in a room and leaving them on after they go to work. They just don't understand that electricity costs money! Here's my options: 1) Let them continue to do this until we get the first month's electricity bill (split it 4 ways), but thereby screw myself to teach them a lesson. 2) Come up with some retribution mechanism like every time you leave a light on you have to put some amount of money in a jar that will go to the electricity bill -- but how do you enforce this? What amount of money is appropriate? 3) Suck it up 4) Go ballistic on them Any advice?