Best Thermoses 2021

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These stylish containers guarantee steaming hot coffee and ice-cold water.

Call it a thermos, travel mug, or insulated water bottle, there’s no substitute for one of these multipurpose containers when you want to keep your drinks hot or cold. The best ones do so for longer and have other features, such as wide-mouth openings that make them easier to fill, clean, and add ice. They’re durable, less prone to leaking, and lighter than those that came before. We put a wide crop through the testing wringer to determine which tick those boxes.

Most rely on double-wall or even triple-wall construction, and the space between each wall is vacuum-sealed. Because it’s devoid of air, this gap slows the transfer of heat. Simply stated: The less air, the less heat flow. Insulated windows work the same way. You have two or three panes of glass joined in one sealed assembly, and each pane of glass is separated not by air but an inert gas that’s a poor conductor of heat. Scottish physicist and chemist James Dewar noticed this effect and, in 1892, invented the vacuum flask, a container with an inside and outside wall separated by a vacuum. Dewar’s flask was the forerunner of today’s thermos. The gap between the container’s inside and outside walls doesn’t have to be wide, it just needs to be absent of air to be effective.

It’s simple to maintain a thermos. Try not to drop it or bang it around, which may break its vacuum seal. Keep it clean, and make sure to remove and give the lid’s gasket a good scrub every once in a while. Most thermoses aren’t dishwasher-safe. Sometimes their lids are, but the bottle may not be rated to withstand the thermal cycle of a dishwasher. Three of the bottles on this list are, but when in doubt, wash by hand. For the bottles with a narrow mouth, you might find a bottle brush helpful.

While we won’t do a deep dive into thermodynamics here, suffice it to say that a wide range of factors can influence the temperature of the liquid in a thermos. To keep the contents hot or cold, stash the thermos in a place that’s hot or cold. Say you want your coffee to stay hot on a winter day, keep the thermos in a pack surrounded by something that will insulate it. Or leave it in your car, especially if there’s sun coming through the windows. If the contents should stay cold, put the thermos in the shade or a cooler. Be mindful of where you set the thermos down. For example, placing it on hot asphalt during a picnic will increase the rate of heat flow from the pavement to the thermos. Your ice-cold water will warm up more quickly. Yes, a thermos with an insulated lid and a vacuum seal at its base resists heat loss or gain more than other designs. But regardless of the construction, with a little common sense you’ll reduce the rate at which the thermos reaches temperature equilibrium with its surroundings.

We put 30 thermoses to the test to see which will keep your hot liquid hot the longest and which will protect that nice chilled drink from heating up.

The hot test: We filled each thermos to the very top (as high as we could without spilling) with 190-degree Fahrenheit water. We then closed the lids and let them sit for 24 hours. Before opening, we shook them to distribute any hot water that may have risen to the top, then tested each with the same infrared thermometer that measured the starting temperature. We then emptied the bottles and let them sit for three hours so that all parts of the bottles would return to room temperature, without retaining any heat from our earlier tests, before continuing to part two.

The cold test: We filled each bottle to the very brim with chilled water, all thermometer-confirmed at a cool 46 degrees. Again, we sealed up the bottles and let them sit for 24 hours. The next day we shook them, opened each, and checked the temperature.

Using these measurements, we calculated the heat loss for our hot test and heat gain for our cold test. For both, a smaller number is preferred. We also used these bottles as you will, seeing how easy they are to drink from, close, open, toss into a bag, and clean. We wanted to see how well they’d fit into our life to know how well they’ll fit into yours.

Weight: 1 lb 8 oz | Other sizes: 28, 64 oz | Lid styles: Screw top, flip top, thermal cup cap, chug cap, shaker | Heat loss (hot test): 65° F | Heat gain (cold test): 10° F

The Elevation is an incredibly impressive thermos with strong thermal retention and a good lineup of accessories that give it an edge over competitors. The 36-ounce model comes standard with a screw-top lid, which we used for our temperature testing. Otterbox has an entire system of lids that work with this bottle, though, including an easy-flip (but not as water-tight) sipping lid, a robust thermal lid like you might see on traditional thermos, and a cocktail shaker top that performed more reliably on a week-long vacation than some actual shakers we’ve used at home. We like that the lids can mix and match with other Otterbox vessels. The screw-top has a great handle and is easy to open and close. It’s not the easiest to sip out of on the move, but we’ll overlook it thanks to the impressive insulation for hot and cold liquids.We love the bright color options for the Elevation, and the powder-coated finish made it a bit grippier in our hands (though we didn’t experience any slipping with the stainless-steel version, either). The bottle’s hearty construction showed no wear after we banged it around in the car, threw it into packs, and plunked it downs on counters. The Elevation strikes a rare balance between superb insulation and ease of use that made it the stand-out winner.

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Weight: 15.2 oz | Other sizes: 14, 18, 32, 40, 64, 84 oz | Lid styles: Screw top, flip top, straw, chug cap | Heat loss (hot test): 66° F | Heat gain (cold test): 5° F

With an average 4.7 star rating based on nearly 21,000 Amazon reviews, the Summit is on par with high-end thermoses in performance—but not price. Not to mention, it’s the only bottle on our list that comes with two lids: an insulated screw top and a flip top (the other compatible options are available for purchase separately). We used both to drink from but stuck with the screw top during the quantitative portions of our test. Although the Summit fell just behind the Elevation at keeping liquids hot, the chilled water stayed 5 degrees colder than the Editors’ Choice winner. That made for swigs that were more refreshing on afternoon walks and all-day hikes.

The flip-top lid didn’t leak and has a comfortable built-in handle if you don’t have a pack or bag with you. But drinking from it was only okay. Its flow rate wasn’t as good as others, and the cover proved very challenging to open. For the first week of use, we needed both thumbs to pop the lid, and though it has loosened some, it still requires a forceful push. Once open, though, the flip top secures in place so it didn’t fall against our face as we drank. The Summit is available in dozens of colors, including ombres and solids. Whatever you choose, treat the bottle with care. Our test model sustained several small nicks in the powder-coated surface after falling onto a gravel lot from a car tailgate. Luckily, the thermal performance wasn’t impacted.

Weight: 1 lb 2.3 oz | Other Sizes: 25 oz | Lid Styles: Screw top | Heat Loss (hot test): 60° F | Heat Gain (cold test): 10° F

We’ll admit we were first drawn to the Beckridge for the sleek brushed-metal exterior. But it’s more than a pretty bottle. It ranked among the top performers in our thermal testing, and Avana adds thoughtful touches. The Beckridge matched the insulating power of the Elevation in the cold test and bested it and the Summit in the hot test. But its innovative easy-to-drink-from spout, which has a straw and a regular brim for big gulps, lends itself more to colder liquids. In that regard, we appreciated that we didn’t have to remove the drinking mechanism to fill the bottle with full-size ice cubes. This contender for our top spot also has a grippy rubber bottom—so it’s less liable to shift on flat surfaces—and a retractable stainless steel carry loop that surprisingly and thankfully didn’t dig in when we used it. Like all bottles this size, the Beckridge unfortunately doesn’t fit in cup holders, but it’s a sacrifice we’re willing to live with.

Weight: 1 lb 2.3 oz | Other sizes: 20, 32, 64 oz | Lid styles: Screw top, straw lid | Heat loss (hot test): 76.5° F | Heat gain (cold test): 3.4° F

After testing the lion’s share of Hydro Flask drinkware, we can definitively say the 40-ounce Wide Mouth is the best of the bunch. The large capacity provides plenty of space for hydrating water and leaves you enough room to bring hot cocoa to share after getting in some turns at the local ski resort. The wide opening let in small and large ice cubes without a fuss. Moreover, this dishwasher-safe bottle touts consistently great thermal retention. The boiling water from our hot test was still noticeably warmer than room temperature after 24 hours. Similarly, the refrigerated water remained cool and refreshing, even with the high-flow straw lid. Fair warning: This Hydro Flask is north of one pound to start and only gets heavier the more you fill it. Plus, the wider base won’t fit in most cup holders or squeeze inside backpack water bottle pockets (ones that don’t have elastic, at least). Still, when it comes to insulation and durability, you’ll get your money’s worth.

Weight: 5.7 oz | Other sizes: 16 oz | Lid styles: Spring-assisted flip-top | Heat loss (hot test): 84.6° F | Heat gain (cold test): 13.3° F

The unicorn of travel mugs is one that combines the drinking convenience of a sipping lid with the thermal efficiency of a screw-top. This ultralight Zojirushi model comes pretty damn close to that ideal. With one hand, we could hold the bottle, slide open the lid lock, depress the button to flip the lid backward, and close it back up after taking a sip. If that sounds complicated on paper, trust us that it’s much more intuitive in reality. We like that the lid is leakproof and disassembles easily for deep cleans. You’ll need a brush to reach beyond the bottle’s narrow opening and scrub the non-stick interior, though.

As for its insulation chops, the SM-SE36 outperformed the next best travel mug in our hot test by a whopping 14.2 degrees and most other options by 20 degrees or more. It’s still not on par with bottles that have traditional thermos lids, but the tradeoff for a user-friendly lid was worth it to us. Our coffee and tea poured from the spout quickly, though the flow wasn’t very steady. A minor irritant, but a smoother stream is about the only thing that could make this otherwise excellent mug better.

Weight: 1 lb 6.6 oz | Other sizes: 17-oz bottle / 12-oz cup | Lid styles: Screw top, sip cap | Heat loss (hot test): 85.4° F | Heat gain (cold test): 9.2° F

Some thermoses swap lids to transition from use with hot beverages to cold. The MultiBev, which CamelBak introduced this past summer, goes a step further by offering two lids and two containers. There’s a 22-ounce bottle with a screw-on lid. But unscrew the lower portion of the bottle and remove the foldable silicone sip cap from the main lid and you have a 16-ounce travel mug. The innovative, space-saving design is well executed. The mug parts stayed securely in place, without rattling, when we used the MultiBev as a water bottle. But they deployed easily when we toted a vat of coffee to a local park or simply wanted it to stay at temperature longer than it would in a French press at home.

It’s worth noting that the silicone cap doesn’t have a closure over the drinking spout. Still, the mug was much better to drink from than the “cup” portion of a thermal cup cap was. We were pleasantly surprised that the tall and narrow build isn’t top-heavy. The silicone base further prevents the thermos from sliding on tables and countertops. Lastly, the MultiBev is one of the heaviest and priciest models on our list but not unjustifiably so, especially for a two-in-one vessel.

Weight: 16 oz | Other sizes: 18, 26, 36, 46 oz | Lid styles: HotShot cap, screw-in, straw, thermal cup cap, chug cap, MagDock cap | Heat loss (hot test): 112° F | Heat gain (cold test): 16° F

Yeti’s Rambler bottles come in a variety of sizes. But this convenient 12-ounce, sold and tested with the HotShot Cap (Yeti’s take on a coffee lid), is great for morning joe. That lid is the best for coffee that we tested. While we had to use two hands to open it—one to hold the thermos, and the other to pinch and twist the lid’s interior rim with thumb and index finger—we loved how easy it was to drink from. We didn’t have to think about which side to tilt, since coffee flows from the center of the lid out over the interior edge in any direction you tip it. And when we closed it tightly, there was no leaking. In addition to the HotShot Cap, the Rambler bottles are compatible with five other lids. Among them, the chug and MagDock caps stand out. Both provided a narrower drinking top that prevented spills (our tester has a penchant for dumping water on herself somewhat frequently) while not restricting the flow rate too much. The chug cap features a large handle that was comfortable to carry, while the MagDock has a smaller cap that attaches to a magnet on the side of the lid so you don’t lose it. Another big plus here is that this bottle (and all Rambler drinkware) is dishwasher-safe.

Weight: 1 lb 2 oz | Other sizes: None | Lid styles: Thermal cup cap | Heat loss (hot test): 61° F | Heat gain (cold test): 9° F

The Stanley Adventure has a classic thermal design with a very small opening, a cap that screws into rather than over the bottle’s mouth, and a cup cover. This means it’s far from easy to drink from on the fly, like in the car on your way to work. In order to do so, we had to find somewhere to put the cup cover, then unscrew the supremely tight lid and hold it as we drank through the bottle’s small opening. It’s anything but convenient, and there are no alternative lid options. But with that inconvenience comes Stanley’s hallmark performance: exceptional insulation of both hot and cold beverages. And what really makes this bottle stand out is that you get those stats for a very affordable price.

So if you’re looking for something to take soup to work or to enjoy a hot toddy, then this bottle is your friend. It has the same rugged (read “heavy”) construction that has made Stanley bottles the standard across generations. And while it won’t break anytime soon, if you lose it, a replacement won’t cost that much.

Adrienne Donica tested hiking, camping, and other adventure gear as Popular Mechanics' outdoors editor, before going on to edit gear reviews for Popular Mechanics, Runner's World, and Bicycling as Expert Reviews editor. Find her on the trail, working on her latest cocktail project, or eating mint chocolate chip ice cream.

Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he’s not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.

James Lynch is Popular Mechanic’s Field Editor looking for stories across the U.S. about those building a better America. He’s passionate about the Erie Canal and the Apollo Space Program.

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