The idea here is simple. If your home is using more power than the average of other homes on wattvision, your home gets a red roof. If your home is using less than the average, it's got a green roof. It's a quick way to see how you're doing relative to everyone else on wattvision. Here are some images from the wattvision map:
Behind the scenes, wattvision compares your present energy use with the 'system-wide average' -- the average of all users on wattvision -- every few minutes. So you can actively work to get your house to have a green roof in just a matter of minutes, ensuring yourself a place among those working to save the environment while saving some money. Your comments are appreciated!