---
title: "How Long Food Stays Safe in a Refrigerator Without Power — a South Florida Answer"
description: "USDA safe windows for a refrigerator and freezer during a power outage, the 40°F rule, what to keep and what to discard, and how to prepare a built-in Sub-Zero for"
url: "https://subzeromiami.support/blog/how-long-food-stays-safe-without-power/"
date_modified: "2026-08-16"
Category: "Safety & Risks"
---


# How Long Food Stays Safe in a Refrigerator Without Power — a South Florida Answer

## The numbers, first

These come from the USDA's food safety guidance and they are the ones to plan around.

| Situation | How long food stays safe |
| --- | --- |
| Refrigerator, door kept closed | About 4 hours |
| Freezer, full, door kept closed | About 48 hours |
| Freezer, half full, door kept closed | About 24 hours |
| Perishable food held above 40°F | 2 hours, then discard |

Every one of those assumes **the door stays shut**. A refrigerator with the door closed is a cooler with good insulation; a refrigerator that gets opened every twenty minutes to check on things is a cupboard. Opening it to look is the most common way people cut the four hours in half.

## Why 40°F is the number that matters

The hours in that table are estimates for a typical unit in a typical room. **40°F is not an estimate — it is the line.**

Below 40°F, bacterial growth on perishable food is slow enough that the food stays safe. Above it, growth accelerates, and the USDA's guidance is that perishables held above 40°F for more than two hours should be discarded.

That is why a thermometer beats a clock. A well-insulated built-in in a cool room may still be at 38°F after six hours. A unit in a hot kitchen with a weak door gasket may be at 45°F after three. If you know the temperature, you do not need to guess at the hours.

**Put a thermometer in each compartment now, before you need it.** An appliance thermometer costs almost nothing and turns the entire question from a judgment call into a reading. After an outage, it is the difference between throwing out a full refrigerator to be safe and keeping most of it because you know it never went above 39°F.

## What to keep and what to throw out

Once power is back and the compartment has been above 40°F for more than two hours, the rule is simple and unforgiving: **discard perishables, whatever they look like.**

**Discard:** meat, poultry, fish and shellfish; eggs and egg dishes; milk, cream, yogurt, soft cheese and cottage cheese; cooked leftovers and casseroles; cut fruit and cut vegetables; soft or cooked pasta and rice; opened baby food and formula; cream-based sauces and dressings; anything with mayonnaise that was already opened.

**Usually fine:** hard cheeses; butter and margarine; whole uncut fruit and vegetables; opened jars of jam, jelly, mustard, ketchup, relish and olives; peanut butter; bread and pastries without cream; fruit juices and unopened bottled drinks.

**The freezer is a separate judgment.** Food that still contains ice crystals, or that has stayed at or below 40°F, can be refrozen — with some loss of quality, not of safety. Food that has fully thawed and warmed above 40°F for more than two hours should go.

**Never taste food to decide.** The organisms that cause foodborne illness do not reliably change how food smells or tastes. Food that smells fine can make you seriously ill, and the amount you have to taste to check is enough to do it. When you cannot establish the temperature history, throw it out — the cost of a refrigerator's contents is not close to the cost of being wrong.

## The coin trick, for outages you slept through

The problem with all of this is that you often do not know what happened. The power went at some point in the night, came back at some point before you woke up, and the freezer is cold now — but was it cold the whole time?

There is a decades-old solution and it works.

- Fill a small cup or shallow container with water and freeze it solid.- Put a coin on top of the ice.- Leave it in the freezer permanently.

If you come home and the coin is still on the surface, the freezer never thawed. If the coin has sunk to the middle or the bottom, the contents thawed and refroze, and you now know to treat the food accordingly. It costs nothing and it answers the one question nobody else can.

## Preparing a built-in before a storm

This is where being in South Florida changes the advice. A hurricane outage is not a four-hour inconvenience — it can run for days, and everybody's plan gets tested at once.

**A built-in cannot be moved.** No wheeling it to a neighbor's generator, no putting it in the truck. Whatever cold it is going to have, it has to already be holding. That shifts the whole strategy from restoring cold to storing it.

**Fill the freezer before the storm.** A full freezer holds roughly twice as long as a half-empty one, because the frozen mass is the thermal store. Freeze bottles or containers of water in the days before — they cost nothing, they fill the space, and afterward they are drinking water.

**Consolidate.** Move what is genuinely perishable from the refrigerator into the freezer before the outage. The freezer is the compartment with the long window; the refrigerator's four hours will be gone before the first band clears.

**Turn both compartments to their coldest setting a day ahead**, so everything starts colder.

**Have a cooler and ice ready** for medication, baby formula and anything that will not fit.

**Know your building's rules.** In a lot of Miami-Dade and Broward condo towers, the generator carries the elevators, the corridors and the pumps — not the kitchen circuits in the units. Assume your refrigerator is on its own unless you have confirmed otherwise.

## After the power comes back

The outage is over. The unit is not necessarily fine.

**Check that it is actually cooling, not just lit.** Lights and a display prove there is power, not that the compressor is running. Put a thermometer in and check it four hours later.

**Expect it to take hours, not minutes.** A unit that has been off for a day is pulling a whole cabinet of warm mass back down. Give it time before deciding it has a problem.

**Watch for the specific ways an outage damages a refrigerator.** The restoration itself is often harder on the electronics than the outage: surges and brownouts as the grid comes back are exactly what kills control boards. If your unit powers up but behaves strangely — a display that does not respond, a compartment that will not come down, a compressor that will not start — that is a real diagnosis with a name, and we have a page for it: [not cooling after a power outage](/symptoms/not-cooling-after-power-outage/).

**A surge protector is worth more here than most places.** Not a guarantee, but the cheapest insurance available against the failure mode that follows every storm season — and there is more on which kind to buy, and why a desk power strip is not one, in [powering a Sub-Zero safely](/blog/powering-a-sub-zero-safely/).

## When to call somebody

Call if the unit does not restart, if it powers up but does not cool within a few hours, if there is a service code on the display, or if it is making a noise it did not make before.

Do not call because the food is ruined and you want somebody to confirm it. The table at the top of this page is the same information a technician would give you at the door, and it is free.

If it is the unit rather than the food, tell us the model number and what happened — how long the power was out, and what the unit did when it came back. After a storm those two details decide whether it needs a part or a reset, and they are the difference between a slot this week and a slot next week.

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