How long will food last in a freezer without power?

Disclaimer: The information below should be regarded as informal advice based on our research. Health and safety guidelines and policies are subject to change. Businesses should always refer to the latest official Food Standards Agency (FSA) guidance and contact their Local Authority's food safety team if they have any queries.

How long will food last in a freezer without power? The answer mostly depends upon how full your freezer is when the power goes down. For most businesses, the freezer will be fully stocked. The FSA states that food can be stored for up to two days (48 hours) in a full freezer providing the door is kept sealed.

If your freezer is half full, you have up to one day (24h) to restore the power before the clock starts really ticking down. Again, the door must remain sealed throughout.

The problem with posting these figures is that people often just type in, 'How long will food last in a freezer without power,' glance at the top search results and take the basic facts at face value without looking at the detail.

If you read the FSA advice carefully, you will see that these values are estimates that can vary due to the make and model of your freezer and the ambient temperature. We would also add that the quality of your door seals (gaskets) will play a big role (more on that later).

Preparing your freezer for a power cut

The most important step you can take if you are expecting a power cut is to buy an appliance thermometer. This will ensure that you can measure the temperature of your thawing food once the power is back on.

If you rely on the FSA estimates alone, you could be putting the safety of customers at risk. What if the power went off intermittently the night before your failure? What if your freezer's temperature was already too high before the power went off?

It is also a good idea to get hold of some blankets. Insulating your freezer during a power cut will slow heat transfer (but make sure you keep the vents clear).

Should it stay or should you throw?

Once the power has been restored, it's time to spring into action. Immediately place your appliance thermometer inside the freezer and take measurements from various parts.

If the temperature is 5°C or below, then you can theoretically refreeze any food in that part of the freezer. If you see ice crystals on the food, this is another sign that the food should be safe to refreeze.

You can theoretically refreeze items that have been above 5°C for two hours or less, but this adds extra risk and will reduce the quality of the food in any case. It is best to immediately dispose of high risk foods, such as meat, poultry, fish and soft dairy products, if they have crept above 5°C. The same applies to foods which contain these items (e.g., cream-based sauces, meat-topped pizzas, custard-filled pastries, etc.)

Some foods can be refrozen even if they have thawed. These include hard cheeses, bread, whole fruits and vinegar-based dressings.

Others, such as sugar-based preservatives and fruit juices may need careful checking for the appearance of mould.

We recommend following the mantra, 'When in doubt, throw it out!'

Caution: could faulty door seals be a hidden threat?

If you're asking, 'How long will food last in a freezer without power?', chances are you are either expecting a power cut (e.g., due to severe weather or planned maintenance) or you have experienced a freezer breakdown.

If it's the latter, this could be a sign of a faulty door seal because this would cause your freezer's processor to work much harder than it's designed to.

If your power has been restored within the 24 or 48 hour period stated above but the interior is above 5°C, your freezer could be letting in more heat than normal. This is another possible sign of a damaged or poor-fitted door seal.

We recommend regularly checking the integrity of your gaskets to avoid a nasty surprise further down the line. If you need new gaskets, we can quickly and easily source or manufacture replacements. Take a look at our website to find out how.