how long does a freezer keep food frozen?

If you lose power how long will the freezer unit in an upright fridge or in a chest type freezer keep food safe after the power goes out?
What can be done to extend the time?
Does filling empty space in the freezer with water bottles and freezing them while you still have power help?

scafool, I recently had the opportunity to gather hard data on this. A windstorm took out the 15KV supply to my parents' house while they were on holiday; I was on duty as Generator Man for the better part of three days.

Horizontal (chest) freezers:

If packed dead full, in a cool location (basement) will last for 24 hours plus. If you don't open the lid, and pack blankets around them (unplug to avoid fire hazard upon startup), you could probably push that by another 24. You might sacrifice food quality by mild defrosting, but I don't think food safety would be compromised. Though I would keep a close eye on seafood for example.

If not packed full, 8-12 hours is the best you'll get. I was getting the first signs of thawing in a 1/3 full freezer that held freshly processes garden vegetables. It helps a lot to consolidate the food at the bottom, drop in whatever ice you have, and pack a blanket in there (or even lots of sheets of newspaper); anything that's a barrier to air movement is helpful. I spread out a blanket on top as well; hard to tell how much that mattered, though it couldn't hurt.

Vertical fridge/freezers:

These are generally much worse. 12 hours max. if it's packed full of hard-frozen blocks, and as little as 6 hours if it's small odds and ends.

I had to stick a sign on the old vertical side-by-side fridge/freezer ... "freezer has partially thawed, don't trust it." Everything stayed at fridge temperatures, and could be cooked and eaten right away; but refreezing some items (pork, seafood) is asking for trouble AFAIK.

If I had packed in extra ice and blankets (or crumpled newspaper I suppose) I could have stretched out the timeline, but by the time I got there the deed was done.

Bottom line:
In all cases: ice and insulation are your friends, and open air space is your enemy.

Most freezers have a "fast freeze" setting, this bypasses the thermostat and runs the compresor continualy, thus cooling the freezer to a lower temperature than normal.

If a power failure is expected, then useing the fast freeze setting before hand will extend the holding time.

Whilst some power failures are random, many result from bad weather, wildfires and industrial disputes.
In such circumstances use of the fast freez setting in advance would help.

Food which is defrosted but still cold should be safe to eat if cooked promptly, but most would advise against re freezing.

For homes that are regulary left unattended it might be prudent to place in the freezer a thermometer that records the MAXIMUM temperature reached.
This would warn the owner if the freezer had defrosted and refrozen whilst they were away.

If the meat is still edible but you can't cook and eat it all, contact your friends with dogs and ask if they have any interest in feeding some raw meat. My vet, a proponent of feeding raw, says that dogs have a shorter gut than humans, and there is no problem whatsoever in thawing meat and then refreezing it for dogs.

Or you can do as our neighbors in Vegas did, when their freezer accidentally got unplugged during some construction: hold a neighborhood BBQ! YUM!

Yes and no. Dogs can tolerate a greater range of bacteria without becoming ill. However, they can and do become sick (perhaps more importantly they can become reservoirs of bacteria pathogenic to humans Camplyobacter - Pets as Reservoirs ) if the pathogenic bacteria overwhelm their natural defenses Campylobacter Infections in Dogs. With that said, I would feel confident feeding my dog refrozen beef (not hamburger) raw. I would likely cook refrozen hamburger, pork and chicken before feeding to my dogs.


Pete

Put duct tape around the seal of the fridge to extend the thaw time. Did this on an igloo cooler with ice in it, put it in our canoe, put gear all around it and on top of it, opened it once a day to take the evening meal out of it, and still managed to keep ice in it till late on day five of a ten day trip in Utah. If putting a blanket on top of the items BEFORE shutting it up, remember that the blanket was at the ambient room temperature before putting it in the freezer. It would be helpful to have the blanket as close to the freezer temp as possible before storing it.
If needed, take a picture of the loaded freezer and refer to where everything is before opening the door, as this will help redice the time needed to get it out.

A practical alternative to getting the min/max thermometer to monitor freezer temps is to simply place a handful of frozen ice cubes in a sealed plastic baggy or other covered container.

As long as the power remains on and the fridge/freezer is properly operational, the ice cubes will remain intact. If the power is lost or the fridge/freezer has a malfunction the ice cubes will start melting when their temp reaches 0+C or 32+F.

You can also make a reasonably educated guess as to how long the power was off by looking at the amount of melting of the ice cubes in instances where the power was offline for several hours and was subsequently restored, thus preventing all the ice cubes melting.

If you come back and find that the ice cubes melted and have the resultant liquid has been refrozen in the shape of the container, then you are reasonably sure that the food in the fridge/freezer may have issues and should be considered as suspect for consumption.

We started doing this as a regular activity after coming back from vacation and finding that the house had a power loss. We ended up tossing all the food (composted some, fed some to the dogs) since we were unsure about it's status due to various neighbors providing conflicting information about the length of the power outage.

The utility company was not much help regarding questions about the length of the power outage, they just said that x number of customers had been without power and could not provide detailed enough information regarding locations and durations for our comfort.

Regards,
Comanche7

There are 'freezer monitors' available that can be set up to tell you what the temperature gets up to and for how long. Typically they are small battery powered units that either maintain a continuous log or start logging when a set temperature is reached. Most seem to have buzzers and/or small lights to give you quick status readings. The more complex ones will feed a detailed log to a computer.

Used to be these were high-end items that were prohibitively costly and used only in industrial plants and places like blood banks where temperature excursions were very costly or dangerous. Prices have come down, $25 to $75 roughly last time I checked, and the units have become much more user friendly.

My experience with an older, low-end refrigerator/freezer has been that in four hours the refrigerator compartment becomes a fetid swamp and the freezer is on the verge of becoming unfrozen. If I run the refrigerator thirty minutes every two hours the temperatures remain within acceptable limits.

My power plan is to hook a small generator to a set of large deep-cycle batteries running an inverter. Using all the excess power from the generator I can charge the batteries. With charged batteries and the inverter I can run smaller loads while the generator handles the larger loads like the refrigerator that can be run a shot time every so often. Shifting loads I can keep pretty much everything running that I need.

Should the generator fail or the loads prove too much I can run a second inverter off my vehicle. In effect turning my car into a generator to make up the difference or to limp along in a somewhat less satisfactory manner.

I really like Comanche 7's idea for a low-tech thermometer.

I am assuming that they should be kept near the outside of whatever is in the freezer, maybe on the top of everything else or in the door tray.

Don't forget the lemon and sea food trick.

Not as good as right out of the ocean with a splash of lemon and down the throat.. but hey it works

Coordinate with your neighbours? Agree the order in which you will open your freezer doors. Whoever's turn it is next, shares their food with everyone else. Everyone else keeps their own freezer doors closed, not even peaking. Hopefully that way, the last freezer to be opened will still be cold.

I don't know how much difference this would make. Some sources say the freezer will only keep food cold for 24 hours, in which case it hardly matters and you'll all have more food than you can eat anyway. Other sources say 48 hours, and in fact I've seen several comments saying their food was still frozen solid after 48. I suspect with a well-stocked and lagged chest freezer, in winter, the food might be edible (after cooking) after as many as 5 days.