How do I defrost a freezer?

Defrosting a freezer without damaging it, keeping the food safe, and preventing heavy ice building up again.

Difficulty: beginner
Time: 4 hr
Read: 2 min
Safety: caution

Short answer

Move the food into cool bags or a neighbour's freezer, switch the appliance off, and let the ice melt with bowls of hot water inside to speed it up. Never chip at ice with anything sharp — puncturing the cooling circuit destroys the appliance.

Ice build-up reduces a freezer's efficiency and its usable space. Frost-free models handle it automatically; older ones need defrosting when the ice reaches about a centimetre. The one rule is never to attack the ice with anything hard or sharp.

Safety

Never use a knife, screwdriver or ice pick to remove ice. The cooling circuit runs close behind the inner lining and puncturing it releases refrigerant and permanently destroys the appliance. Keep frozen food below 8°C throughout — food that has fully thawed should be cooked or discarded rather than refrozen.

What you'll need

Cool bags or boxes
Towels
Bowls of hot water
Plastic scraper
Wet vacuum (optional)

Step by step

Run the freezer stocks down first if you can plan ahead.Less food to move and less to keep cold. A week of eating from the freezer makes the job far easier.
Move the food into cool bags with ice packs, or a neighbour's freezer.Packed tightly together, food stays frozen for several hours. Keep it below 8°C throughout.
Switch the appliance off at the socket.Not just the dial. You will be putting water inside it.
Put towels around the base and inside to catch meltwater.There is more water than expected, and it runs out of the door as the ice releases.
Place bowls of hot water inside and close the door.The steam loosens ice from the walls far faster than air alone. Replace the water as it cools.
Ease loosened sheets of ice off with a plastic scraper.Plastic only. Never anything metal or sharp — see the safety note.
Wash the interior with a bicarbonate solution and dry it thoroughly.Dry completely, or the residual moisture immediately becomes new frost.
Switch it back on and let it reach temperature before reloading.Around -18°C. Loading a warm freezer thaws the food you are putting back in.

Tips

A wet vacuum removes meltwater as it goes and turns a wet job into a manageable one.
Heavy ice build-up often means the door seal is failing. Test it by closing the door on a sheet of paper — if it slides out easily, the seal needs cleaning or replacing.
Keeping the freezer reasonably full helps it hold temperature and run more efficiently.

Common mistakes

Chipping ice with a knife or screwdriver — The cooling circuit sits behind the lining. Puncturing it destroys the appliance beyond repair.
Refreezing food that has fully thawed — It should be cooked first, or discarded. Refreezing thawed raw food is a food safety risk.
Reloading before the freezer is back to temperature — It partially thaws the food you are putting back in.

Questions people ask

How often should I defrost a freezer?

When the ice reaches about a centimetre thick, which is typically once or twice a year for a manual-defrost model. Frost-free appliances handle it themselves.

Can I refreeze food that has started to thaw?

If it is still below 8°C and has ice crystals, it can usually be refrozen with some quality loss. Fully thawed raw food should be cooked before refreezing, or discarded.