Refrigerators and freezers account for about a sixth of all electricity use in a typical home. Over- or under-crowding makes the fridge work harder to maintain its optimal internal temp around 37 degrees F. This means that you should throw out all that junk that piles out in your fridge, but if it gets empty fill your fridge with bottles of water and freezer with ice trays. This way you can throw a cocktail party and keep your energy usage down.