Our home food freezer (ca. 14cu ft) is bigger than we really need. I am planning to fill one shelf with 8-12 gallon jugs of water, with the intent of using its high latent heat of fusion to help keep the contents cold during a power outage. Is this volume actually enough to make a meaningful difference? Would this improve the efficiency during regular operation? (I am presuming cold air in the unused volume warms up very quickly, thus needing to be cooled down again.) Could this be improved by adding something to lower the water's freezing point?