Food Safety During a Power Outage: What to Keep and Toss

The three numbers to remember

Appliance	Safe time with the door shut
Refrigerator	About 4 hours
Freezer, full	About 48 hours
Freezer, half full	About 24 hours

These times assume the doors stay closed. Each opening lets cold air out and shortens them.

The temperature rule

The line that matters is 40°F (4°C). Bacteria multiply quickly above it. Perishable food that has been above 40°F for more than 2 hours should be thrown out. That includes meat, poultry, fish, eggs, milk, soft cheese, cooked leftovers and cut fruit.

An appliance thermometer in the fridge and another in the freezer removes the guesswork. They cost a few dollars, and they are the only way to know what happened while you were asleep or away.

While the power is out

Note the time the outage began.
Keep both doors shut. Decide what you need before you open one, then be quick.
After about 4 hours, move the most perishable fridge items into a cooler with ice or frozen gel packs.
Group frozen food tightly together so it stays cold longer.
In freezing weather, do not store food outside. Sun can warm it even on a cold day, and animals will find it. Freeze containers of water outdoors and bring the ice inside to the cooler.

When the power comes back

Fridge: if the outage lasted under 4 hours and the door stayed shut, the food is fine. If it lasted longer, check the thermometer and discard perishable items that were above 40°F (4°C) for more than 2 hours.
Freezer: food that still has ice crystals, or is at 40°F (4°C) or below, can be refrozen or cooked. Quality may suffer, but it is safe.
Never taste food to test it. Food can look and smell normal and still make you ill.

What usually survives

Hard cheeses, butter, whole uncut fruit and vegetables, bread, jam, mustard, ketchup, peanut butter and most vinegar-based sauces tolerate a warm spell. When in doubt, check the official chart linked below, which lists foods one by one.

When is backup power worth it?

For an outage of a few hours, a closed door is all you need. Backup power starts to pay for itself when outages run past a day, or when the freezer holds a lot of meat or a season's garden produce.

You do not have to run the appliances continuously. Powering a fridge and freezer for an hour or two, a few times a day, is often enough to hold safe temperatures and uses far less battery or fuel. Use the thermometers to confirm it is working.

A typical modern fridge and a separate freezer together might use around 1.8 kWh a day. At 90% usable capacity, that is a 2,000 Wh battery for 24 hours. The fridge and freezer calculator works this out from your own figures.

Medicine

Some medicines, including insulin, need refrigeration. Ask your pharmacist ahead of time how long yours can stay unrefrigerated and what to do if it gets warm. A small cooler with ice packs is a sensible standby.

Sources

Reviewed October 2026 by Lee Palmer. This guide is general information, not professional advice. Suggest a correction.

Food safety during a power outage