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Keeping a fridge and freezer cold in an outage
FDA time limits for an unopened refrigerator and freezer, and how to use a power-station calculator without treating the result as a food-safety test.
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The first move when the power fails is to leave the doors shut. The U.S. Food and Drug Administration says a refrigerator will keep food cold for about 4 hours if it is unopened, and a full freezer will hold temperature for about 48 hours if the door stays closed. A freezer that is half full holds for about 24 hours, again if it stays closed. Those are FDA’s figures for the insulated box, not a promise about any battery.
Before the outage
FDA’s outage page asks you to put an appliance thermometer in the fridge and the freezer, with the freezer at or below 0 °F and the refrigerator at or below 40 °F. The thermometer is how you know whether the food is still cold when the power returns. Group food in the freezer so the mass stays cold longer. Freeze water jugs ahead of time if you want extra cold mass and, if the tap is unsafe later, melt water. Know where you could buy block ice or dry ice. FDA says fifty pounds of dry ice should keep an 18-cubic-foot fully stocked freezer cold for two days. Handle dry ice with the ventilation and skin protection the seller describes. This page is not a dry-ice manual.
If you expect a long outage, cook or eat perishable food while it is still at a safe temperature, and cook it to a safe internal temperature. FDA says perishable food held at room temperature for 2 hours or more should be discarded, or 1 hour if the outdoor temperature is above 90 °F.
When the power comes back
If a freezer thermometer reads 40 °F or below, FDA says the food is safe and may be refrozen. If you did not have a thermometer, FDA says you cannot rely on appearance or odor. Food that still has ice crystals or is at 40 °F or below may be refrozen or cooked. Refrigerated perishable food — meat, poultry, seafood, milk, eggs, leftovers — that has been above 40 °F for 4 hours or more should be discarded. FDA also says perishable food that was not kept adequately cold may cause illness even if it is cooked afterward. When you are unsure, throw it out. This site is not a medical diagnosis. If you think someone has a foodborne illness, contact a healthcare provider. FDA lists its food-information line as 1-888-INFO-FDA (1-888-463-6332).
Floodwater is a separate problem. Do not eat food that touched flood water. FDA’s page has the container rules. Follow that page rather than a summary if flood water reached the kitchen.
Using a power station
A station can run a fridge only if it can both start the compressor and keep up with the average load. Starting watts are often much higher than the running watts printed in a shopping table. On a model page here, continuous watts and surge or peak watts are separate fields. If surge is unknown, the calculator will say the starting-watt check cannot be completed. Do not type a guessed surge into that box and treat the pass as a manufacturer rating.
The calculator’s fridge presets are planning assumptions: example running watts, example starting watts, and a duty cycle such as 0.3 or 0.35 because a compressor cycles. They are not a measurement of your refrigerator. Replace them with the nameplate. Depth of discharge and inverter efficiency are also assumptions unless you are copying a figure the manufacturer actually published. None of the station records in this catalog include a recommended depth of discharge.
Idle draw matters. Jackery’s support articles for some Explorer models state a standby consumption, and those records prefill it. If idle draw is unknown and you leave it at zero, the runtime is longer than a station that uses power just by being on. The result is still arithmetic. It is not a test, and it does not override FDA’s clock. If you are not confident the fridge stayed at or below 40 °F, the food rule is the FDA rule, not the battery estimate.
A small station can fail a full-size refrigerator on surge even when the watt-hour capacity looks large. Read both numbers. X-Boost or SurgePad, where a brand publishes them, are not automatically added to the continuous rating on this site.
Medicines that must stay cold need a plan from the pharmacist or clinician. Do not assume a fridge runtime estimate covers them.
Sources
- FDA, Food and water safety during power outages and floods, retrieved 7 November 2026.
- Ready.gov, Power outages, on keeping refrigerator and freezer doors closed, retrieved 7 November 2026.
- BlackoutSmart runtime calculator, for the formula and the labeled assumptions.