Simple steps to keep food frozen longer in a power outage: fill gaps, add ice blocks, group food, use a thermometer and keep the door closed.
- A full, tightly packed freezer holds cold much longer than a half-empty one.
- Frozen water bottles fill gaps and later become drinking water.
- An appliance thermometer and a closed door are your two best tools.
A full freezer is a big stock of food, and it is worth protecting. The good news is that a freezer is built to hold cold well, and a few easy habits stretch that time even further.
The standard guidance from Canadian and US food safety agencies is that a full freezer will keep food safely frozen for about 48 hours if the door stays closed, and a half-full freezer for about 24 hours. A fridge keeps food safe for about 4 hours. Those are guides, not guarantees. For the full rules on what to keep and what to throw out, see fridge and freezer food safety in a power outage.
Fill empty space
Air warms up fast, but frozen food and ice hold cold. A freezer with a lot of empty space loses cold sooner, so fill the gaps.
- Freeze water in clean plastic bottles, jugs or food containers. Leave a little room at the top, since water expands as it freezes.
- Use gel freezer packs from the camping aisle or a lunch bag.
- Fill bags with ice cubes and seal them. These also work as drinking water when they melt, if the bag is clean and food-safe.
- In a pinch, bread, paper bags or crumpled newspaper can fill empty space and reduce air movement, though ice does a better job.
Frozen water bottles do double duty. They keep the freezer cold, and as they melt they give you cold drinking water. Our water storage guide shows how much to plan for.
Group food together
Packing food close together helps it stay cold, like ice cubes in a glass. Push everything to one side or into the centre, and consider putting meat and poultry on a tray or in a bin at the bottom, so juices do not drip on other foods as things thaw.
Grouping also makes it quicker to find what you need, which means the door stays open for less time.
Set the temperature right
Freezers should hold -18 degrees C (0 degrees F) or colder. If a storm is on the way and you have notice, you can turn the freezer to its coldest setting a day or so ahead, then return it to normal afterward. Do the same for the fridge, aiming for 4 degrees C (40 degrees F) or colder.
Use an appliance thermometer
Do not guess. A cheap appliance thermometer sitting in the freezer tells you the real temperature, and it also tells you something important after the power comes back: whether food stayed cold enough. A thermometer that reads -18 degrees C (0 degrees F) or below means the freezer held its cold. A good trick is to put a coin on top of a frozen cup of water. If the coin has sunk to the bottom when you return, the contents thawed completely and then refroze, and the food may not be safe.
Keep the door closed
Every time the door opens, cold air spills out and warm air flows in. Decide what you need before you open it, take it out quickly, and close it. Tell everyone in the house the freezer is off limits, and put a note on the door if that helps.
A chest freezer holds cold better than an upright one because cold air sinks and stays inside when you lift the lid. If you have both, use the chest freezer for long-term items.
Add insulation and shade
- Keep the freezer in a cool place, out of direct sun.
- Cover a chest freezer with blankets or a sleeping bag to add insulation, but do not block any vents.
- If the freezer is in a garage or basement in winter, check that it does not get so cold the compressor has trouble, and see manufacturer guidance.
Backup options for longer outages
For an outage that runs past a day, you have a few choices.
- Run the freezer off a power station or generator. See what size power station you need and how to use a portable generator safely.
- Move food to a cooler with plenty of ice, or to a neighbour's or relative's working freezer.
- Use dry ice, following the supplier's handling instructions. It needs good ventilation and gloves, and must never be sealed in an airtight container.
- Cook and eat the thawing food first, starting with the most perishable items.
Please also read neighbour check-ins during a power outage, since sharing freezer space is a good way to help each other.
After the power returns
Check each item. Food that still has ice crystals or feels as cold as if it were in the fridge can usually be refrozen or cooked. Food that has been above 4 degrees C (40 degrees F) for more than 2 hours should be thrown out. When in doubt, throw it out.
Quick answers
How long will a freezer stay frozen without power?
Official guidance says about 48 hours if full, about 24 hours if half full, as long as the door stays closed. Treat this as a rule of thumb.
Should I refreeze thawed food?
Food that still has ice crystals or is still at fridge-cold temperature can generally be refrozen, but quality may drop. If it was warm for more than 2 hours, discard it.