Can You Leave a Slow Cooker On Overnight?

As a single dad with 3 kids who runs his own business making healthy delicious meals for my kids can be tricky. A slow cooker is a great way to make those meals for them.

But can you leave a slow cooker on overnight? Can I prep the food at night when the kids are asleep and then leave it to cook while everyone is in bed?

You can leave a slow cooker on overnight as long as temperatures stay above 140ºF (60ºC) but it may dry out or burn. The “low” or “keep warm setting is usually 145-165ºF (63-74ºC) and according to the USDA this will keep food safe for eating indefinitely.

So whether you're putting your slow cooker on to cook your meal overnight so it's ready in the morning or you've already got a cooked meal and you would rather keep it warm instead of putting it in the fridge or freezer then it's fine to keep it for extended periods of time in a slow cooker.

Will Food Go Bad in a Slow Cooker Overnight?

I know that slow cookers are safe to leave unattended for a long period of time, but my biggest concern is food safety.

Will the food go bad, get spoiled or be dangerous to eat if left in a slow cooker overnight?

Your food should not go bad if left in a slow cooker overnight as long as the slow cooker is on. The slow cooker keeps food at a temperature of 145-165ºF (63-74ºC) which stops bacteria growth. You food may get dry or change in flavor though.

But how do I know this is the case? If it was me I'm not just going to trust some random Dad blogger and what he says. I want details from a reputable organization about whether or not this is likely to make me sick.

Well it turns out the USDA has looked into the issue of keeping hot food safe for long periods of time.

They had this committee meeting on hot holding temperatures and in their notes they state:

the Committee concluded that a minimum temperature of 135 degrees for a maximum of 8 hours, or a minimum temperature of 140 degrees Fahrenheit indefinitely also would be adequate to ensure food safety.

USDA Committee on Microbiological Criteria for Foods

There are also some other precautions you want to take to ensure the food in your slow cooker is safe to eat

Heat Food Above 165ºF (74ºC)

Above you can see an image of the “danger zone”. This is the temperature range where bacteria can grow and multiply.

Once you get above 140ºF (60ºC) it becomes too hot for most bacteria and they die off.

However you can also see that for some types of food the temperature is higher. Poultry for example needs to be kept above 165ºF (74ºC).

It's also recommended that if you're reheating food you raise the temperature to above 165ºF (74ºC) for at least 15 seconds and then you can store at 140ºF (60ºC) for a longer period of time.

This time on the increase heat will kill off most bacteria, making it safer to keep the food at a lower temperature.

With a slow cooker it usually cooks above 165ºF (74ºC) anyway before it switches to “Keep Warm” so you should be fine.

Food That Is Not Kept Properly Prior To Cooking Can Be Dangerous

Some foods, like raw meats, if not kept properly can grow bacteria that produce heat resistant toxins.

While cooking this food above 165ºF (74ºC) or hotter may kill the bacteria it may not remove the toxins that are already in the food.

So if food has gone bad prior to you cooking it in the slow cooker then don't use it as it could still have toxins in there.

Keeping it warm overnight is unlikely to add to these toxins, but it's also unlikely to remove them.

Is It Bad To Leave a Slow Cooker On Overnight? Will It Overheat?

What about electronically? Is it bad to leave a slow cooker on overnight or for long periods of time?

Could it potentially overheat and start a fire? The answer is yes, but it's incredibly unlikely.

It's highly unlikely that your slow cooker will start a fire if left overnight but it is technically possible. Brittle power chords can cause sparks and electric fires. So make sure you follow the safety instructions and have a smoke detector in your kitchen.

According to the federal emergency management agency caused 103 fires from 2012-2015 but that's a tiny number compared to fires other appliances have caused. In the same time frame there were 63,784 fires caused by other appliances.

You can see in the video below a house that caught on fire, presumably by a slow cooker.

So it's incredibly unlikely that your slow cooker will start a fire while you're sleeping but you do want to have a smoke detector working just in case.

Will Food Dry Out If Left In a Slow Cooker?

If you leave food in a slow cooker overnight will the food dry out?

While slow cookers use lids to retain most of the moisture they do lose moisture slowly over time.

If you're keeping your slow cooker on warm overnight you want to make sure it has enough liquid/moisture in it otherwise the food will dry out.

Even the “Keep Warm” setting is usually between 145-165ºF (63-74ºC). While not super hot this is still cooking your food slowly and it still creates a lot of evaporation.

Can I Leave a Cooked Meal on ‘Warm' In a Slow Cooker Overnight?

If you've had food cooking in your slow cooker all day and you've got some leftovers or you didn't end up eating it that night can you simply leave it on the “Keep Warm” setting overnight or will the food go bad?

The “Keep Warm” setting on slow cookers is usually between 145-165ºF (63-74ºC) which, according to the USDA, is hot enough to keep food safe and bacteria free indefinitely. So you can leave a cooked meal on warm in a slow cooker overnight without issue.

Keeping food hot is actually a medieval method of safe food storage and slow cookers keep food out of the “danger zone” where bacteria can grow and multiply and spoil your food and potentially make you sick.

Slow cookers generally do have a 24 hour timer though after which they turn themselves off. So you'll just want to make sure your slow cooker doesn't turn itself off or your food will enter the danger zone and if it's in that temperature range for more than 1-2 hours then it won't be ok to eat.