When the power goes out in the home, minimize opening the refrigerator and freezer. Refrigerators and freezers are insulated, aiding in keeping foods cold. However, if the refrigerator or freezer door is opened often, the cooling will be lost. Perishable refrigerated foods (i.e. foods of animal origin) should be discarded after a 6-hour period. Using block ice may increase shelf-life of refrigerated foods. Food stored in fully loaded freezers may last for approximately two days, whereas food stored in partially loaded freezers may last for only one day. Freezer foods may be refrozen if ice crystals are present. Exceptions include ice cream, pizza, and casseroles. If the frozen food has completely thawed but is cold, it must be cooked within a 24-hour period; or foods may be refrozen within 24 hours after thawing. However, quality may be diminished. If in doubt about when the food actually thawed in the freezer, discard the thawed food. Dry ice may be used to keep frozen foods frozen and cold foods cold. Be careful not to handle dry ice with bare hands or breathe the vapors.
(Source: Virginia Tech - Food Storage Guidelines For Consumers - Virginia Cooperative Extension)