How long does a freezer stay cold without power?

By SGWNI. Checked on 2 November 2026.

A full freezer should keep food frozen for up to 48 hours in a power cut, and a half-full one for up to 24 hours, as long as the door stays shut. Those are the Food Standards Agency’s figures, and the FSA calls them estimates. If the power is off for less than 4 hours, it says this is unlikely to affect the safety of chilled or frozen food.

The fastest way to work out where you stand is the power cut food checker. The rest of this page explains the reasoning.

What changes the time

• How full it is. A packed freezer holds its cold for longer. Those two figures are the only ones the FSA gives, so if yours is somewhere in between, plan on the shorter one.
• The door. The FSA’s first instruction is to keep fridge and freezer doors closed as much as possible. Each time you open the door, warm air gets in.
• The room. The FSA says the temperature of the room can raise the temperature inside, more so if the doors are opened often. A warm kitchen will shorten the time.
• The type of freezer. The USDA says the freezer compartment in a fridge may not keep food frozen as long as a separate freezer.

What you can do in the first few minutes

Write down the time the power went off. Every decision later depends on it.

If the freezer isn’t full, the USDA suggests grouping packages together so they keep each other cold. It also suggests moving raw meat and poultry away from other food, so that juices can’t drip onto anything if they start to thaw.

Then shut the door and leave it shut. A freezer thermometer kept inside will tell you far more than lifting packets out. A freezer normally runs at -18°C.

Getting ready for next time

Citizens Advice suggests filling plastic bottles with water and putting them in the gaps in your freezer, which helps it stay colder for longer. Leave some room at the top of each bottle, because water expands as it freezes.

When the power comes back

Don’t refreeze food that has thawed. The FSA’s power cut advice doesn’t cover refreezing, but Food Standards Scotland says not to refreeze food that thawed while the power was cut. Food that’s still frozen solid hasn’t thawed, so it can stay in the freezer.

The FSA’s general advice is to use food within 24 hours of it fully defrosting. You can freeze it again once it’s cooked, but then reheat it only once. GOV.UK’s guidance on food labels gives the same 24 hours for food frozen before its use-by date.

The FSA also says what to eat first if you’re using up food during a long cut: chilled food, then defrosted frozen food that doesn’t need cooking, then perishable food kept at room temperature, and tinned, bottled and dried food last.

The most detailed food-by-food chart we know of is American, from FoodSafety.gov. It’s shown here as extra guidance on what to throw away, and it isn’t UK advice. It’s more relaxed than the UK rule: it allows refreezing that we don’t. So we use it only to help you decide what to discard.

If frozen food has been at 4°C or above for more than 2 hours, the chart says to discard:

• meat, poultry and seafood of all kinds
• stews, soups and casseroles
• milk, soft cheese and shredded cheese
• eggs out of the shell
• cheesecake, and cakes or pastries with a custard or cheese filling
• ready meals, frozen pizza and meat pies
• vegetables and vegetable juices, once they’ve been above 4°C for 6 hours

It also says to discard ice cream and frozen yoghurt, even if they still have ice crystals.

The chart is more relaxed about foods like bread, hard cheese and flour. We still wouldn’t refreeze them: eat them within 24 hours, and throw away anything with mould, a yeasty smell or sliminess. The power cut food checker goes through this food by food.

If you’re feeding someone at higher risk

The FSA says young children, pregnant women, older people and people with underlying health conditions are at greater risk of food poisoning. For them it advises care with high-risk foods such as deli meats and smoked fish, making sure food is steaming hot, and not eating food that has passed its date or spoiled.

Our own view is to be stricter still for these households. If you’re cooking for someone in one of these groups, we’d throw out anything that has thawed and might not have stayed cold.

Two rules that always apply

Never taste food to find out if it’s safe. Food that has been kept too warm can look and smell normal.

When in doubt, throw it out. A freezer of food is a real loss, but it’s a smaller one than a bout of food poisoning.