How long does a freezer stay frozen in a power cut?
About 48 hours for a full freezer and 24 hours for a half-full one, if the door stays shut. A fridge keeps food cold for about four hours. Those are the figures the UK Food Standards Agency and the US Department of Agriculture both give. They are estimates: an old freezer, a warm kitchen or a door opened to look inside all shorten them.
What to do when the power goes
- Keep the doors shut. Every opening lets the cold out. Decide what you need for the day, take it out once, and put it in a cool box.
- Note the time. The four-hour and 48-hour clocks start when the power went off, not when you noticed.
- Check a thermometer, not the clock. A fridge thermometer tells you whether the food really stayed cold. The FSA says a fridge is still fine during a power cut while it stays below 8 °C; once it reaches 8 °C or more, food that normally needs refrigerating should be eaten within four hours.
- Fill the gaps. A full freezer holds its cold longer than a half-empty one. Frozen bottles of water and ice packs kept in the freezer before a storm fill the space and double as ice for the cool box.
The two cheap things that help
Fridge and freezer thermometers. The only way to know whether the food stayed cold enough, rather than guessing from the clock.
Look for: One for each appliance, readable without opening the door for long.
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When the power comes back
The USDA says food in the freezer that still contains ice crystals, or has stayed at 4 °C (40 °F) or below, can safely be refrozen, though its quality may suffer. Anything perishable that sat above that temperature for more than two hours should be thrown away. If you cannot tell, throw it out: never taste food to decide whether it is safe.
What a power station adds
A freezer is one of the jobs a battery does well, because the compressor only runs part of the time. A 1,056 Wh Anker SOLIX C1000 runs a chest freezer for about 15 h 3 min and a fridge-freezer for about 14 h 29 min on this site's model.
Because a full freezer holds its cold for a day or more on its own, you do not need to run it continuously. Running it for an hour or two every few hours stretches the same battery much further, and a thermometer tells you when it needs another turn.
Size a station for your freezer Power cut essentials
The fridge duty cycle guide explains why a fridge averages far less than its label, and the US outage list covers coolers and stored water.
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