True or False? A full freezer is more efficient than a half-filled freezer. Answer? True. A full freezer is more efficient. Once something freezes it helps in keeping the surrounding items cool, and its volume reduces the amount of air circulation needed in the freezer box. This means the unit's compressor needs to run less often which saves energy. If you have excess freezer space a couple of empty plastic bottles filled with water will work just as well as TV dinners.