This post explains the differences in how long food stays hot inside a thermos between the most popular brands, keeping the food hot, and selecting the right container for your needs.
While manufacturers advertise how long their brand keeps food hot, some things can help you get the most out of your container so the thermos lunch stays warm until lunchtime.
How long does a thermos keep food hot
The amount of time you need to keep food hot will depend on when you pack the lunch and heat the food and when it will be consumed. On average, most of us need to keep food hot between 6 and 7 hours.
Depending on your brand of thermos lunch container, food will stay hot for between 5 and 12 hours, so the one you purchase matters.
Check out this comparison chart by brand and price:
| Brand | Hours Hot | Price (avg) |
|---|---|---|
| Thermos Foogo | up to 5 | $15 |
| Thermos Funtainer | up to 5 | $15 |
| Bentgo | up to 6 | $29 |
| Stanley Classic | up to 12 | $22 |
| Stanley Heritage | up to 8 | $24 |
| Mira | up to 5 | $16 |
| Omiebox | up to 4 | $45 |
| Lunchbots Wide | up to 5 | $34 |
| Lunchbots Classic | up to 6 | $20 |
Learn more about the features of each of those insulated containers here.
How to keep food hot in a thermos for Lunch
The best way to keep the food hot as long as possible inside the thermos container is to heat it up properly before transferring it into the thermos. This means the food should be heated up piping hot, meaning too hot even to taste!
You can also preheat the thermos by filling it with boiling water and letting the heat warm up the metal sides and the air space between the double insulated walls.
Is it safe to keep food warm in a thermos?
Food that was cooked and stored properly makes a terrific thermos lunch. The thermos’s job is to keep the food at a safe-to-eat temperature for hours after being heated up properly and packed inside.
The time between when you warm up the food to when it will be enjoyed determines which thermos container is best for you! For this reason, most brands list an approximate time of how long it will retain the food’s temperature inside the insulated walls of the container.
How to Pack Hot and Cold Lunch Together
Packing hot and cold lunch foods inside the same lunch bag is possible by placing the hot food inside a thermos and the cold items, such as fruits and veggies, separately.
If you need to add an ice pack to keep other food items chilled, place it away from the thermos container that’s keeping the warm foods and near the cold food items.
Here is a quick video showing you how to pack hot and cold lunches the right way:
Best Hot Food Thermoses
Three things make up the best thermos container for your lunches; how much food it can hold, how long it will keep the food hot inside, and the features that make it age-appropriate for your child; meaning ease of opening and getting the food out.
Tip: if you’re packing food in a thermos for the first time, let your child try it at home first so they can open and close the container independently.
Here are 3 great performing thermoses:
You can't go wrong with any of the options above for packing lunches. A thermos is a terrific vessel for repurposing leftovers and sending hot and cold foods for lunch! A great place to start is with these delicious thermos soup recipes.
Julie Moussot says
I have been using Thermos Foogo containers for years with good success. To pre-heat the container, I add boiling water and screw on the lid while I heat the food. Just dump the water and refill with lunch and you will be goo to go!
Brittany says
Any suggestions on how to pack a thermos in a lunch box with cold items, such as juice box or yogurt?
Rachel says
Lisa from 100 Days had a whole post about how pre-heating the thermos has no effect on how the food keeps its heat. Thoughts?
MOMables says
While I respect Lisa and her process very much, I was curious about this. I took the time to preheat and test the thermoses as shown. The temperature is clearly different. To me, it is worth taking the minute to preheat.
Karen Lynne says
Have you continued to use the Stanley thermos with success? Most of the reviews I read said they only lasted a few weeks before the seal broke. Evidently, they are now made in China, and the quality isn’t up to previous expectations. What has your experience been?
MOMables says
2 years going strong. the reason the seal breaks is because people are putting it in the dishwasher. The lid should be hand washed.
Rebecca says
Laura,
I struggle with keeping foods (other than soup) above 140 degrees from 7:15am to 12:15pm which is the time between when my sons lunch is packed and eaten. Any further advice? I’ve reheated spaghetti and marinara on the stove. I can only heat it to about a maximum of 180 degrees without burning it before putting it in a thermos preheated with boiling water. I’ve tested the temperature and after 2 hours using the funtainer thermos you recommended and it is in the neighborhood of 130 degrees which concerns me because for the remaining 3 hours it would be in the danger zone. I’m still so puzzled as to how to tackle a safe hot lunch. Thanks so much for your thoughts.
MOMables says
Rebecca, the foods we tested in our tests were heated in a microwave (sorry!) stirring often to prevent hot spots. As a mother of 3, I am less concerned with “safe temperature issues” in winter than summer. My biggest concern is where my kids’ hands have been (school bathroom… gross) rather than food that I’ve prepared at home and cooked it thoroughly the first time. Of course, you have to do what’s best for your family and I am glad you are testing this for your own precautions.
Rebecca says
Thanks so much for your additional thoughts on keeping hot lunches hot and safe Laura. I too am most concerned about clean hands at lunch time. I actually pack a mini alcohol based hand sanitizer in my son’s lunch !
Connie says
To keep lunches hot I heat food really hot, like said above. I also put boiling water in the canister to heat the container. And remove it, just before adding the food. That’s way your food doesn’t start cooling down right away from putting the food into a cold canister.
MOMables says
Exactly what I preach. Thanks Connie!
Stephanie says
I just want to say Thank You for your suggestion about keeping my child’s food hot in a thermos. I wouldn’t have thought about it. My son is so happy that he can have other foods besides PB & J or bagels.
Thank you again. Can’t wait to see what other ideas you have.
Rosa says
Do you know of any rectangular container that can keep food warm? Something that the kids can open up and eat in like a small plate? I currently use a Thermos too but the mouth of the container is small. Short of using 2 Thermoses, is there one that can keep 2 different foods warm while keeping them separate? My son does not like the sauce or meats mixed with the pasta or rice.
MOMables says
I’ve searched everywhere an there are no square/rectangular thermos containers out there. I wish!
C says
Do you keep foods besides soups warm? Weird question but my daughter loves sauteed shrimp and asked if I could pack her some in her stainless thermos. Do you think it would remain warm and safe even though it won’t be completely full? My husband is convinced that this is a horrible idea.
MOMables says
I use a thermos more often for other leftovers than just soup! A thermos is a wonderful idea. If your food was cooked to a safe temperature for dinner, reheating it and placing it in a thermos will be no problem.
Laurie says
Hey, C! Since shrimp take almost no time at all to cook completely, I’d recommend actually starting with raw shrimp in the morning. It might take an extra minute or two in the morning, but if you’ve prepped them for dinner, then they’re ready to cook.
Just make sure to hold boiling water in the thermos until ready to place the freshly cooked shrimp into it. I’ve done this myself for shrimp and seafood dishes, and haven’t had a cold. or otherwise unappetizing dish yet.
Anna says
What if my child’s lunch time isn’t until 6-7 hours after? I leave for work in the morning at 6:15 AM, dropping him off at the extended hours program. (He eats breakfast there). Lunch isn’t until after noon.
MOMables says
I use a thermos too. The food will still be warm.