How long food lasts in the fridge and freezer when the power is out

Before an outage: two thermometers and some ice

The most useful preparation is cheap: an appliance thermometer in the refrigerator and another in the freezer. USDA guidance says the refrigerator should be at 40°F or below and the freezer at 0°F or below. After an outage, these thermometers tell you exactly how warm the food got, so you are not guessing.

A few more things help:

• Freeze containers of water or gel packs ahead of time. They help keep the freezer cold and can go into a cooler later.
• Keep the freezer as full as you reasonably can. A full freezer holds its temperature about twice as long as a half-full one.
• Have a cooler ready, and know where you could buy ice or dry ice nearby.

During an outage: keep the doors closed

Every time the door opens, cold air spills out. Decide what you need before you open the refrigerator, take it out quickly, and close the door.

If the power has been out for about 4 hours and is not coming back soon, move perishable food from the refrigerator into a cooler with ice or frozen gel packs. USDA notes that 50 pounds of dry ice should keep a full 18-cubic-foot freezer cold for about 2 days. Handle dry ice with gloves, keep it in a ventilated space, and follow the seller’s instructions.

In winter, is outside a refrigerator?

It is tempting, but outdoor temperatures swing, sunlight can warm a container, and animals get into food. A closed cooler with ice, kept in a cold room and checked with a thermometer, is easier to control than a snowbank. If you do use the cold outside, keep food sealed in a cooler and check its temperature.

After an outage: what to keep and what to toss

• Check the thermometers first. If the refrigerator stayed at 40°F or below, the food is generally fine.
• Perishables above 40°F for 2 hours or more go. That includes meat, poultry, fish, eggs, and leftovers.
• Frozen food can be refrozen if it still has ice crystals or is at 40°F or below. The quality may suffer, but USDA says safety does not.
• Check each item separately. Throw out anything that touched raw meat juices.
• Throw out food that touched flood water unless it is in undamaged, waterproof, commercially sealed packaging.

Medications that need refrigeration

Some medicines, including insulin, need to stay cool. The FDA says insulin vials and cartridges, opened or unopened, can be kept unrefrigerated between 59°F and 86°F for up to 28 days and still work. Keep insulin away from direct heat and sunlight, and do not use insulin that has frozen. For any other refrigerated medicine, check the label or ask your pharmacist what to do if it warms up.

Keeping the refrigerator running instead

If you would rather power the refrigerator through a long outage, a battery station or generator can do it, but plan for both the energy and the brief surge when the compressor starts. Using the calculator’s default values, a refrigerator alone for 24 hours comes to about 1,639 Wh after the loss buffer and reserve. Your refrigerator may use more or less, so check its label and adjust the numbers.

Estimate your refrigerator’s needs

Short checklist

• Put appliance thermometers in the refrigerator and freezer.
• Freeze water containers or gel packs.
• Keep a cooler where you can reach it.
• Keep the doors closed during an outage.
• After about 4 hours, move perishables to a cooler with ice.
• Toss perishables that sat above 40°F for 2 hours or more.
• Know the storage rules for any refrigerated medicine.

Sources and safety references

• Keeping Food Safe During an Emergency (external, USDA Food Safety and Inspection Service)
• Three Ways to Keep Food Safe When You Lose Power (external, FoodSafety.gov)
• Information Regarding Insulin Storage and Switching Between Products in an Emergency (external, FDA)
• Avoiding Carbon Monoxide Poisoning (external, CDC)