When your freezer is full you will get the best performance and functionality from it. Each frozen item helps keep the others frozen. This keeps the temperature low as well as your energy costs. If your freezer is less than full, you can remedy this with a clean milk or juice jug that has been filled 3/4 of the way with water. When you add this to your freezer it will do the same job as frozen food. Always leave a little air between your items so the cold air can circulate.