Best Thermoses of 2018

Nicole Johnston ·
Internet Security & Appliance Editor
Updated
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We spent over 100 hours testing thermoses, insulated flasks and food vacuum jars, and our favorite is the Isosteel Vacuum Flask. This well-designed and durable thermos keeps liquids hot for 24 hours or cold for 48 and has the lowest heat loss rate of all thermoses we tested. The insulated walls keep the outside of this thermos from heating up or cooling down and prevents condensation from building. The Isosteel easily fits into your car’s cup holders, holds 30 ounces of your favorite drink and comes with a five-year warranty.  

Best Overall
Isosteel Vacuum Flask
The Isosteel Vacuum Flask holds enough liquid to keep you hydrated for a while, or to share a drink or two with a friend. It keeps your drink hot for 24 hours or cold for 48.
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Best Value
Hydro Flask Standard Mouth
The Hydro Flask insulated travel thermos comes with a lifetime warranty and is available in three different sizes and 11 colors.
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Best Food Thermos
Zojirushi Stainless Steel Food Jar
The Zojirushi Stainless Steel Food Jar keeps food and beverages warm or cool for up to six hours and has a wide mouth so it’s easy to ladle food in and spoon food out.
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Product
Price
OVERALL RATING
Value
Test Results
Construction
Suggested Manufacturer Price
Warranty
Claimed Hours Hot
Heat Lost After Claimed Hours (degrees F)
Heat Retention After 2 Hours
Claimed Hours Cold
Warm Up After Claimed Hours (degrees F)
Leak-Proof
Fits In Car Cup Holder
Fits In Stroller Cup Holder
Liquids
Foods
BPA Free
Vacuum Sealed
Double-walled or Insulated
Stainless Steal Walls
Dishwasher Safe
Number of Fluid Ounces
Height (inches)
Width (inches)
Weight (ounces)
Base Diameter
$41.6 Amazon
5 5 4.5
$18.95
5 Years
24
-64
96
48
.+27
Yes
Yes
No
N/A
30
12.2
3
18
3
$19.81 Amazon Warehouse
4.5 5 4.5
$40
Lifetime
24
-65
95
24
.+15
Yes
No
No
N/A
35
14.25
4.5
30.4
4.5
$27.95 Amazon
5 4.5 4.5
$29.95
Lifetime
12
-76
86
24
.+29
Yes
Yes
No
N/A
18
8.4
2.9
11
2.9
$15.5 Amazon Marketplace
4 5 5
$15.50
30 Days
5
-40
84
10
.+20
Yes
Yes
No
N/A
13.5
5
3.2
13.6
3.2
$21.32 Midland Hardware
3.5 5 5
$24.99
30 Days
12
-54
91
24
.+18
Yes
Yes
Yes
X
16
9.8
2.9
8
2.9
$28.78 Amazon
4 4.5 5
$28.99
5 Years
6
-38
91
6
.+36
Yes
No
No
N/A
25
7.2
4
14.1
4
$14.69 Amazon
2 4.5 5
$20.99
N/A
5
-57
80
12
.+16
Yes
Yes
No
Lid only
16
7.8
3
16
3.5
$19.95 Amazon Marketplace
2.5 4.5 5
$12.99
N/A
6
-64
82
No Claim
Not Tested
Yes
Yes
No
Lid only
12
5.4
3.5
30.4
3.5
$35.99 The Sportsman's Guide
1 5 5
$39.99
N/A
24
-83
92
24
.+22
Yes
Yes
No
X
26
10.5
4
30.4
3.5
$12.99 Amazon Marketplace
2 3.5 5
$19.99
N/A
3
-55
69
No Claim
Not Tested
No
Yes
Yes
X
10
4.5
3
5.9
3
Best Overall
This vacuum flask is a great thermos to take along with you and holds 30 ounces of liquid. That’s as much as two water bottles, a medium soft drink or a Starbucks Trenta Cold. It keeps your cold liquids chilled for 48 hours or your coffee hot for 24 hours.
Its base is only 3 inches in diameter, which is perfect for fitting nicely into your car’s cup holder (we tried it out just to make sure), but it is too big for standard cup holders on baby strollers. The Isosteel thermos’s cap doubles as a handy cup, and because of the amount of liquid it holds, it can easily be brought along on a road trip or picnic to share a hot or cold drink with a friend. The quick-stop cap keeps spills at bay, even when being jostled and bumped in a backpack (we tested this too!), and you can remove the cap to drink straight from the thermos itself. The mouth of this thermos isn’t large enough to cover your nose while drinking, but it is wide enough to easily fit standard size ice cubes through it. The BPA-free insulated walls of the Isosteel Vacuum Flask keeps the inside temperature from reaching the outside so while you are carrying it around, you can’t tell if the liquid inside is hot or cold. This also helps keep condensation from forming, which tends to make your thermos wet and more difficult to keep ahold of.
Pros
  • Doesn’t lose heat very quickly
  • Holds 30 ounces of liquid
  • Ice cubes fit through the wide mouth
Cons
  • Isn’t dishwasher safe
  • Heavy when full
  • Doesn’t fit in stroller cup holders
US$17.54Amazon
Read the full review
Best Value
The Hydro Flask Standard Mouth insulated thermos is the best value in large part because of the lifetime warranty that comes with it. But it is also a good quality thermos that doesn’t leak when shaken or bounced in a backpack.
This vacuum thermos fits nicely in standard car cup holders and holds 18 ounces of your favorite drink. It keeps coffee hot for 12 hours, though it does lose heat quickly, about 86 percent after two hours. During our tests, the average thermos filled with hot liquid cooled by 76 degrees after 12 hours (from 188 degrees to 117 degrees F), even when we prefilled the thermos to heat the inside before finally filling it. So, this coffee thermos works best if you’re planning on enjoying your drink within a couple hours of pouring it. The insulated walls keep the outside of the thermos from changing temperature, so you can always comfortably hold your drink. It also doesn’t collect condensation. While the Hydro Flask thermos is BPA free, it isn’t dishwasher safe, so you should wash the entire container, including the lid, by hand.
Pros
  • Includes a lifetime warranty
  • Several sizes to choose from
  • Prevents condensation
Cons
  • Loses heat quickly
  • Isn’t dishwasher safe
  • Doesn’t fit in stroller cup holders
$27.95Amazon
Read the full review
Best Food Thermos
The Zojirushi food jar’s wide-neck design lets you ladle hot soup, chili or pasta into the container without making a mess, and it’s equally easy to spoon out the food without contorting your hand in awkward positions. Plus, it keeps food really hot, only cooling down by 38 degrees in the six hours we tested it.
This Zojirushi holds 25 ounces, more than double the amount of other food thermoses we tested, so it’s a good option for middle or high schoolers who need a bigger lunch at school, or for on-the-go adults who need a healthier option than fast food. This food jar keeps cold foods chilled for six hours, too, though Zojirushi does advise against toting raw or cold dairy products in this container. You can place the Stainless Steel Food Jar directly into your child’s backpack because even with all the shaking and bumping, the threaded gasket seal lid stays snuggly sealed and doesn’t leak. As with most thermoses, this one isn’t dishwasher safe, and there have been reports that it can retain odors from extra smelly foods.
Pros
  • Wide mouth for easy use
  • Retains heat well
  • Leak-proof seal
Cons
  • Not suitable for dairy products
  • May retain odors
  • Handwash only
$29.95Amazon
Read the full review
Best Commuter Thermos
The Contigo West Loop thermos is a great choice for commuters because it holds 16 ounces of coffee, keeps it hot for five hours and fits snuggly in most car cup holders. The leak-proof lid has an easy-sip spout that can be unlocked with one hand then re-secured after enjoying a sip.
Plus, you can control how fast the liquid pours out so you’re not surprised with a rush of hot coffee. If you find 16 ounces isn’t enough, Contigo does offer 20-ounce and 24-ounce options. The insulated walls keep the heat inside while keeping the outside walls cool to the touch. Or, if you prefer an iced latte, the thermos will keep it cold for 12 hours on the inside without freezing your fingers on the outside. The Contigo thermos isn’t built to handle foods, so its restricted to drinks only, but its unique lid is dishwasher safe if placed on the top rack. The body of this thermos should be handwashed.
Pros
  • Fits in most car cup holders
Cons
  • Isn’t designed for food
$17.44Amazon
Read the full review
Best for Outdoor Enthusiasts
We were impressed that the Stanley Classic thermos kept hot liquids hot for 24 hours, cold liquids chilled for 24 hours and ice cubes cold for 120 hours (that’s five days.) And because it holds an impressive 35 ounces, the Stanley Classic is perfect for taking along on a fishing trip, hike or picnic.
The Stanley Classic is heavy and bulky because of the amount of insulation used to keep drinks ready when you want them. But its leak-proof cap makes it possible to tote it around in a backpack without worrying about spilling. And the cap doubles as a handy cup so you can share a drink with your travel companion. Its sheer size doesn’t allow the Stanley thermos to fit in a dishwasher (it’s handwash only anyway) or in your car’s cup holder, so it isn’t an easy grab and go option.
Pros
  • Keeps drinks hot or cold for 24 hours
Cons
  • Large and bulky
$40.39Amazon
Read the full review

Why Trust Us

Top Ten Reviews has been researching and testing home products since 2010, and for the past three years we have invested several hundred hours examining thermoses. We looked at a wide variety of thermoses and insulated food containers and spoke with moms, commuters and outdoor enthusiasts who tend to use these items frequently to learn about their experiences with different types of thermoses and the brands they purchase.

For example, Richelle Kimbal, a mother of four, bought an insulated food jar to send hot lunch to school with her second grader during the cold winter months. Kimbal was so impressed with the quality, value and ease of using it that she purchased a second one when another child started all-day school. We used this feedback while examining different characteristics of insulated food jars, such as wide mouths, durability, spill-proofing and ease of washing them. We also considered cost since that is an important determining factor for many people.

Another consumer we spoke with is Anna Burleson, who totes an insulated thermos to the office in the morning with several ounces of coffee. Burleson pointed out that during her commute it’s important that the flow of coffee from the pour spout is consistent to avoid burns, and equally important is to control the speed of the flow. Also, being able to unlock and open the flask with one hand is necessary. With this information we looked closely at pour spouts, cap locks and ease of opening and closing them, plus which thermoses fit into standard car cup holders.

How We Tested

We conducted multiple temperature tests to see if the manufacturer’s claim of how long a thermos keeps food or liquid hot or cold was accurate. After filling each thermos with a consistent hot or cold temperature measured water, we waited for the claimed hours to go by. We then opened the thermoses and remeasured the water to learn how much heat was lost, or how warm cold water became as it sat untouched.

Hot Water Tests
According to a study published by the US National Library of Medicine National Institute of Health, researchers at The University for Texas at Tyler found coffee, tea and other hot beverages are typically served between 160 and 185 degrees F. For heat tests, we added water heated with a sous vide machine to 200 degrees F. When it was transferred to the thermoses, the water cooled to 188 degrees F. We performed multiple tests, with some testers filling thermoses at room temperature and others pre-filling the thermoses with hot water to heat the inside first. We didn’t see much difference in how quickly the water cooled between the pre-filled and non-pre-filled thermoses. On average hot water cooled by 55 degrees after sitting between six and 12 hours, with another 15-degree cooldown at the 12-hour mark. 

We wanted to learn the average heat loss for each thermos, so we filled each pre-filled thermos with 188-degree F hot water then remeasured after only two hours. The best insulated thermoses retained over 90 percent of the water’s heat, though several dipped down to 80 percent heat retention. Only one thermos retained less than 70 percent of its water’s heat after two hours.

Cold Water Tests
As with the heat tests, we started by filling each thermos with water that had been chilled to 33 degrees F, which is 1 degree warmer than water’s freezing point. We noted how long each thermos claimed it could keep water cold, and we measured the water temperature once that time had elapsed. On average the water warmed by 23 degrees to a temperature of about 58 degrees F, still 15 degrees colder than room temperature.

Food Jar Tests
For the three food jars we tested, we wanted to learn how hot the food stayed after sitting in the thermos for six hours, which is the amount of time manufacturers claim their jars keep food warm. We heated soups, chowders and Top Ramen to 187 degrees F, which is 27 degrees hotter than food should be heated to kill any foodborne bacteria. There was a decent difference in heat loss between the food jars with a range of 33 to 66 degrees of cooldown. This still kept foods at a decent, enjoyable temperature after six hours of sitting. 

Leak-Proof Tests
We subjected each thermos to vigorous shaking, tipping, jostling and bouncing to see how tightly the lids sealed. Even the food jars, filled with hot soup, were turned over and tossed to make sure they wouldn’t open in your child’s backpack. With the exception of one thermos, every one kept a very tight seal. The Asobu Imperial Beverage Cup was the only thermos that leaked…a lot. And unfortunately, the first time we performed a leak-proof test with this product the water was a bit hot and caused some burns on the hands of one of our testers. 

Other Tests
In addition to our temperature retention tests, and our leak-proof observations, we also checked out which thermoses fit well in car cup holders and in stroller cup holders. We learned that stroller cup holders are substantially smaller than those in cars and most thermoses don’t fit well. Even most standard water bottles are too big to fit. Kimbal expressed her frustration with not being able to tote along a hot or cold drink during her morning run with two children strapped into her jogging stroller. Instead she places her thermos in the carrying basket under the stroller but mentioned this is very inconvenient since it requires her to stop and bend down to find her drink when she needs to rehydrate. 

How much does a decent thermos cost?

Because there are so many kinds of thermoses and food jars available, there isn’t a clear-cut answer to how much one costs. However, you can expect to spend between $15 and $20 for a decent thermos that is well insulated, holds a good amount of liquid and includes a leak-proof lid. Most thermoses in this price range also come with a warranty to cover major manufacturing defects.

Things to Look for in a Thermos

Whether you are toting icy water to hydrate you after a long workout or bringing warm baby food with you to keep a hungry child happy, having a quality thermos can make or break your outing. Different thermos models have different characteristics, so you’ll need to choose the one that works best for your situation.

Construction & Insulation
Construction and insulation can profoundly affect temperature retention and durability. There are plastic and pressed tin models on the market, but better- quality thermoses give you a double-walled stainless steel construction. This provides strength, scratch resistance, shatterproofing and corrosion resistance. Stainless steel is also able to withstand the pressure of vacuum insulation. This type of insulation maintains temperature with airless space between the two walls of the thermos. This prevents heat or cold leaching into or out of the interior, which means a flask with good quality vacuum insulation holds heat or cold for longer intervals than one with foam insulation.

Capacity
The capacity of a thermos dictates how many people can stay hydrated and for how long. With capacities ranging from 4 ounces to 1 gallon, you should choose the size of your flask based on its most likely use. If, for example, you need a thermos for hiking, family picnics or other all-day or overnight activities, you’ll no doubt need one with a substantial capacity. For your own hydration during a workout or a hot drink on the daily commute, a single-serve travel mug or travel tumbler that holds between 4 and 16 ounces probably would work better.

Features
If you're looking for a thermos that's easy to carry while you run or work out, consider one that comes with a carry strap, clips to your belt or has a contoured body for a comfortable grip. For drinks while driving, opt for a slimline travel mug that fits into a vehicle cup holder. When you require a large-capacity flask, look for one with a carry handle, strap or case. For storing in a backpack or lunchbox or to carry over rough terrain, the flask needs to be airtight so it doesn't leak.