How long does food actually last in my freezer during a blackout?

With the door closed, a full freezer stays cold about 48 hours, a half-full freezer about 24 hours, and a refrigerator about four hours.

Keep the doors closed: a full freezer holds a safe temperature for about 48 hours without power, while a half-full one lasts about 24 hours. An unopened refrigerator protects perishables for only about four hours. Put an appliance thermometer inside now, because food is safe to keep or refreeze only when it still has ice crystals or measures 40°F or below.

Freeze water bottles or jugs to fill empty space; they act as cold mass during an outage and become drinking water later. Never taste food to judge safety. When the temperature history is uncertain, throw it out rather than risk foodborne illness.