When you open your freezer, all the freezing cold air is going to come out. That means when you close it the freezer has to produce more and that can get expensive over time. A way to prevent this is to pack your freezer full of stuff. You can do things like bags of ice or even newspaper if you have it laying around. When your freezer is packed, it keeps the cold air in. That means your freezer works less and uses less electricity.