Do you turn off the lights when you leave a room? Or when you leave your home? What about the TV and stereo? Most of us turn them off too. We do it in order to save energy. We do it because our parents taught us that it is important. Even though the importance is clear, our parents rarely looked at any numbers. Turning off the lights is a nice gesture, but it turns out that this barely makes a difference. So, if we really want to reduce our energy consumption, the question is: What does?