While coolers are mainly designed to keep food and drinks cold their insulating power can also be used to keep things hot for hours at a time.
A good cooler that is prepared correctly can keep food hot for hours or even days at a time even when it's cold outside. This can be great for keeping for hot at a party, or a picnic, during a roadtrip or when travelling.
In this article we'll love at the 7 best ways possible to keep food hot in a cooler. Some of these techniques are super simple and they work!
A Quick Word About Keeping Food Hot Safely
You don't often have to think about food safety and bacteria growth when you're using a cooler to keep things cold, but when you're trying to keep things hot it's a really important thing to consider.
According to the USDA there is a “danger zone” for food which is between 40-140ºF (4.4-60ºC). In between this range bacteria can rapidly grow which can spoil your food and potentially make you sick if you eat it.
For some meats (like poultry) as well as leftovers it's recommended you keep them above 165ºF (74ºC) in order to keep them safe.
Once your food enters into this “danger zone” you'll want to consume it within 1-2 hours so it doesn't have enough time to go bad.
If not properly kept, or if stored in the danger zone for too long your hot food can spoil in your cooler.
To avoid this you'll want to store your food HOT and once the temperature starts to drop below 140-165ºF (60-74ºC) you'll want to eat it within a couple of hours.
How To Keep Food Hot In a Cooler
There are a few methods below that are great at keeping food hot. But they all work off similar principles. Keep these principles in mind when trying to keep food hot.
Pre-Heat Your Food
The rule of keeping food hot is to make your food hot. It's not a great idea to try and warm food up in a cooler.
Coolers don't have a heating element. They can stop heating escaping, thus keeping food hot, but they aren't able to warm food up.
So pre-heat your food and remember, you're heating it to eat later in the day. So make it hotter than eating temperature as it will cool down over time.
Increase Thermal Mass
You know how soup can stay hot for a long period of time but toast gets cold within a couple of minutes coming out of the toaster?
This is because soup (and water) are dense and have a lot of thermal mass, while fluffy bread is light and doesn't have much thermal mass.
Dense foods will stay hot longer than non-dense foods. Adding things like hot water bottles and hot bricks to your cooler increases the overall thermal mass and things will stay hot longer.
Increase Insulation/Decrease Air Space
While a cooler is a good insulator sometimes it needs a little help.
Things like towels and cardboard are actually great materials for insulation and can insulate your hot food, keeping it hot for longer.
Empty air space in your cooler is also the enemy of keeping food hot. So using towels to fill up empty air pockets or using cardboard to create a barrier layer can keep food hot longer.
When food is hot it often lets off steam. As water evaporates from your food it takes a lot of the heat with it.
Wrapping your food up or putting it in a container so steam can't escape will keep it hot longer.
Now that you know the main rules to follow, here are the 7 best ways to keep food hot in a cooler.
1. Pre-Heat Your Cooler With Warm Water
Coolers are made of thick walls of foam which have millions and millions of tiny pockets of air.
These pockets of air are what stops heat getting in or out of your cooler.
When your cooler is kept at room temperature and you put hot food in it then the walls of the cooler (and the pockets of air inside) will steal some heat from your food as they warm up.
This is especially true for expensive coolers like Yeti.
You'll want to pre-heat the walls of your cooler. To do this fill up your cooler with warm water from the tap and leave it to sit for 20-30 minutes to warm up the walls.
Then discard the water, give your cooler a dry down and then put your food inside.
This will extend the time your cooler will keep food and drinks hot as the walls of your cooler won't steal any heat from your items.
Don't use boiling water in your cooler as it'll warp the walls and maybe even melt the insulation. Keep it under around 120ºF (49ºC) for expensive coolers.
2. Wrap The Inside Of The Cooler In Aluminum Foil
Coolers are great at stopping 2 types of heat transfer (convection and conduction) but there is a third type of heat transfer (heat radiation) and coolers are rarely if ever designed to stop this type of heat transfer.
It turns out that aluminum foil is great at reflecting and insulating against heat radiation. It's so good that people carry emergency space blankets which use aluminum to reflect their body heat back and keep them warm. Learn more about aluminum as a good insulator.
Aluminum reflects about 97% of heat radiation, so wrapping the inside of your cooler in a thick layer of aluminum foil, or multiple layers of thin foil can be a great way to trap more heat.
3. Wrap Your Food In Aluminum Foil
While wrapping the inside of your cooler in aluminum foil will increase it's ability to insulate wrapping your food itself in aluminum foil will keep the insulation closer to the food and thus keep the heat in the food better.
Aluminum foil also stops evaporation which is another way to keep food hotter for longer in a cooler.
So wrap your loose food items in aluminum foil and also wrap your food containers in aluminum foil.
4. Add Towels, Cardboard or Newspaper To The Bottom Of Your Cooler and In Air Spaces
Use a bath towel or beach towel on the bottom of your cooler. This will both insulate your food, keeping it away from the walls of the cooler which can sap heat but it'll also protect your plastic cooler from the extreme temperatures of your food.
If your cooler comes in direct contact with extremely hot food then the plastic will warp and the insulation in expensive coolers can melt. So towels are a great way to stop this from happening.
Cardboard or scrunched up newspaper are also great insulators and they can be used instead of towels, or along with towels if needed.
Also use towels, cardboard or newspaper to fill up any empty air pockets in your cooler.
You don't want empty air space as this causes your food to cool down more quickly. So fill these air pockets up.
If your cooler is larger and this isn't feasible use a piece of cardboard cut to the same size as the cooler opening and place it on top of all your hot food/towels to create a barrier layer.
5. Use a Hot Water Bottle or Heat Pack
Hot water bottles filled with boiling water or a heat pack filled with rice is a great way to add extra thermal energy into your cooler.
The extra thermal energy of the hot water bottle will keep the entire inside of the cooler hotter for longer and it'll take longer for your food to cool down.
6. Create Hot Bricks
Hot bricks are another great way to keep food really hot in your cooler. The good thing about these is that they can let off A LOT of heat, keeping food extremely hot and safe for hours.
They are also cheap and easy to make. You just need to be careful not to melt your cooler.
To make a hot brick follow these instructions:
- Wrap a brick in aluminum foil
- Place in the oven at 300ºF (150ºC) for 20-30 minutes
- Place 1-2 towels on the bottom of your cooler to protect it from the extreme heat of the brick
- Place 1 or more bricks in the bottom of your cooler
- Place your food directly on top of the bricks (unless using plastic)
- Place a towel on top of your food and close the lid
- You food will now stay hot for hours
7. Keep Your Cooler Closed
Hot air rises, so every time you open your cooler the warm air is going to escape and be replaced with cool air from the outside.
This will speed up the cooling down process of your food.
To keep your food hot for as long as possible don't open your cooler to check on it and try to keep it closed as much as possible.
Best Coolers For Keeping Food Hot
Not all coolers are created equal and some coolers are better at retaining heat than others.
Generally speaking coolers that are good at holding ice for a long period of time will also be the coolers that perform the best to keep food hot.
You can see my list of the best insulating coolers on the market and choose from that list or I've highlighted a couple of good options below:
Extreme Performance: Kong Coolers
Kong coolers are a newer entrant to the market and they are doing something right because they are currently the best insulating cooler on the market.
They can keep ice longer than any other brand and they are great at insulating and keeping food hot as well. They even outperform well known brands like Yeti, which you can see in my Kong vs Yeti comparison.
They are made in the USA, backed by a limited lifetime warranty and are one of my favorite cooler brands on the market at the moment. I can highly recommend them.
Value-For-Money: Lifetime Coolers
Lifetime coolers are the most affordable high end cooler on the market.
They have similar performance to premium brands and similar features but they sell for a fraction of the price.
While other coolers might cost you over $300 the smaller Lifetime coolers often cost less than $100.
Lifetime coolers are made in the USA, are bear proof and lockable and they can keep food hot all day long. They are the best value for money cooler on the market.
Best Budget Option: Coleman Xtreme
If you don't want to break the bank and you're looking for the best budget cooler to keep food hot then you can't go wrong with the Coleman Xtreme.
It's extremely cheap but it outperforms other cheaper coolers by a good margin, keeping your food warmer for longer.
They are lightweight and durable. I've owned one for 5 years now and it's still going strong.