It's no secret that a full freezer is the most efficient kind, since the majority of the energy used is to cool down warm air. A more packed freezer means less air, which means less energy used to cool things down. But what if your freezer isn't full? You can fill up large bags with Styrofoam packing peanuts to fill up spaces, or reuse freezer bags by filling them with water and freezing them flat to act as ice blocks (and they can be used to keep things cool in ice chests when you need them). Any reusable plastic containers (perhaps from takeout) can be cleaned, filled with water and frozen to help fill your freezer space, too.
ANDREWS MCMEEL SYNDICATION