We Tested 12 Thermoses—Four Were Hot, Hot, Hot

Ah, the humble thermos—once a stalwart of commuters everywhere, these tall, vacuum-insulated bottles have become less common with the rise of cupholder-fitting travel mugs. But while many people prefer their hot coffee in individual portions, let’s face it: sometimes 20 ounces (or less) just doesn’t get the job done. Maybe you want to share some cocoa with friends on a winter hike, or perhaps you like having cups of coffee a day in the office (and it has to be home-brewed)—this is where a large thermos comes in handy.

Compared to travel mugs, thermoses are bigger (usually at least one liter compared to 16 ounces), have thicker vacuum insulation, and have screw-on, leak-proof caps without a sipping port. They’re better at retaining heat for longer periods than travel mugs, and most are secure enough to toss into any bag without fear of coffee (or iced tea) leaking. To find which thermoses have the best insulation, we put 12 models to the test. It’s worth noting that since we originally reviewed thermoses in 2021, our previous top pick from GSI has been discontinued.

The Winners, at a Glance

The Best Thermos

Zojirushi Stainless Bottle SJ-JS10

View On Amazon $34 View On Zojirushi.com

We loved the size of this thermos from Zojirushi, which was almost a half-inch narrower than some other models. It was easy to carry around, and the small wings on the cup lid gave us more leverage when screwing it on and off. We also really liked its pour-through lid, which features a flip mechanism for sealing it back up when you’re done. 

A Classic, Great Thermos

Stanley Classic Vacuum Insulated Bottle

View On Amazon $39

If you’re looking for a classic thermos with great performance, the Stanley Legendary Classic Bottle fits the bill. It kept liquids hot and cold and had a durable construction that held up against dings and drops. 

The Best Portable Thermos

Zojirushi Stainless Bottle SJ-TG08/10

View On Amazon $41 View On Zojirushi.com

With a similar performance to our top pick but in a slightly shorter bottle with a detachable lanyard, this Zojirushi thermos is good for on-the-go. It also has a plastic bumper on its base that helped it avoid damage during our drop test.

The Best Wide Mouth Thermos

MiiR Wide Mouth Water Bottle

View On Amazon $40

We really liked the Miir because it was easy to fill and had a convenient handle lid. While it had a wide mouth, it also had a narrower body than other models, making it easy to fit in or backpack or tote bag. It also comes in a variety of attractive colors and was easy to clean. Though it didn’t perform quite as well as our other top picks, we think its heat and cold retention are more than adequate for everyday use.

The Tests

• Heat Retention Test: We poured boiling water into each thermos and checked the temperature every two hours with an instant-read thermometer to simulate opening and closing the lid to pour. After eight hours, we let the thermoses rest overnight and checked the temperature one last time at 24 hours. 
• Cold Retention Test: We chilled water with ice until it was near 36ºF and then poured it into each thermos and checked the temperature every two hours. After eight hours, we let the thermoses rest overnight and checked the temperature one last time at 24 hours. 
• Leak and Durability Tests: We tilted each thermos on its side over a paper towel to check for any potential leaks. We then dropped each thermos on its lid, side, and bottom corner from three feet up and performed the same leak test. Finally, we held each thermos upside down over the sink and shook it lightly.
• Usability and Cleanup Tests: We evaluated how easy the thermoses were to fill and pour from. We checked how much effort was required to tighten and loosen each cap, and carried every thermos around the house to see how portable they were. Finally, we washed each thermos by hand and ran all dishwasher-safe models through the dishwasher. 

What We Learned

So What Is a Thermos, Anyway? 

Thermoses use vacuum-flask insulation (originally popularized by the Thermos company) to keep liquids hot or cold. Vacuum flasks remove air, creating an insulating barrier between what’s inside the thermos and the ambient temperature around the bottle. That same vacuum insulation is used in all types of drinkware, including thermoses, travel mugs, and water bottles, so we took a slightly broader approach to product selection. Most of the models we tested are traditional thermoses that have at least a one-liter capacity and typically come with a cup lid that you pour your beverage into. We also wanted to test some newer insulated bottles that have a lid with a handle instead of a cup. These models are typically marketed as water bottles but are rated for both hot and cold liquids. 

Only One Model Failed Our Heat Retention Test…and Just Barely

Through all our heat and cold retention tests, almost every thermos performed well enough for most people to be happy with them. The only model that struggled was the YETI Rambler, but that bottle is mostly marketed for cold retention anyway. Buried almost halfway down their FAQ page, YETI states that their Rambler bottles are only rated for a maximum temperature of 185ºF. Still, we tested it with boiling water and it was the only model that dropped below 160ºF after eight hours. However, it did maintain a temperature of 152ºF at the six-hour mark, which is still warmer than our preferred drinking temperature. 

The Thermoses and Their Heat Retention
Product Name	Initial Temp	After 2 hours	After 4 hours	After 6 hours	After 8 hours	After 24 hours
Stanley Legendary Classic Bottle	201ºF	194ºF	183ºF	179ºF	174ºF	135ºF
Zojirushi Stainless SJ-JS10RA	201ºF	191ºF	183ºF	177ºF	171ºF	137ºF
Zojirushi Stainless Bottle SJ-TG10XA	205ºF	195ºF	186ºF	177ºF	172ºF	132ºF
Stanley Classic Insulated Thermos	200ºF	193ºF	186ºF	178ºF	174ºF	137ºF
Miir Wide Mouth Bottle	200ºF	190ºF	178ºF	170ºF	161ºF	119ºF
YETI Rambler 36oz	204ºF	179ºF	163ºF	152ºF	142ºF	100ºF
Otterbox Elevation Growler	203F	190ºF	178ºF	169ºF	161ºF	117ºF
Stanley Adventure To Go	201ºF	192ºF	184ºF	177ºF	170ºF	134ºF

Most models, like the Stanley Legendary Classic Bottle, Stanley Classic Insulated Thermos, the Stanley Adventure To Go, and both Zojirushi thermoses performed very similarly. They all maintained at least 170ºF after eight hours, which is hot enough to burn most people’s tongues. 

Cold Retention Is Easier Than Heat Retention

Every model performed well in the cold retention test. The best-performing bottles (like the Zojirushi Stainless SJ-JS10RA and the Miir Wide Mouth Bottle) only let the temperature rise by 10ºF or less after 24 hours. And while the YETI was at the bottom of the pack (along with the Otterbox Elevation Growler), it only saw a temperature rise of 13ºF. A three-degree difference in cold water isn’t really discernible for most people, though. 

The Thermoses and Their Cold Retention
Product Name	Initial temp	After 2 hours	After 4 hours	After 6 hours	After 8 hours	After 24 hours
Stanley Legendary Classic Bottle	35ºF	36ºF	38ºF	39ºF	39ºF	45ºF
Zojirushi Stainless SJ-JS10RA	36ºF	37ºF	38ºF	38ºF	39ºF	45ºF
Zojirushi Stainless Bottle SJ-TG10XA	35ºF	37ºF	38ºF	38ºF	39ºF	45ºF
Stanley Classic Insulated Thermos	35ºF	36ºF	38ºF	39ºF	39ºF	45ºF
Miir Wide Mouth Bottle	37ºF	38ºF	39ºF	40ºF	42ºF	47ºF
YETI Rambler 36oz	37ºF	38ºF	39ºF	42ºF	43ºF	50ºF
Otterbox Elevation Growler	37ºF	39ºF	40ºF	42ºF	43ºF	51ºF
Stanley Adventure To Go	34ºF	36F	37ºF	38ºF	39ºF	46ºF

Most of the other thermoses performed nearly identically, with temperatures rising only a few degrees during the first eight hours. It’s safe to say, then, that if you like your water (or iced tea) frigid, most of these models would be sufficient for an entire day. 

Cup Lids Provided More Insulation

We didn’t particularly like drinking out of the cup lids (plastic and stainless steel give off some less-than-pleasant flavors, especially with warm beverages), but they did add an extra layer of insulation. Every model we tested with a screw-on cup lid (including the Zojirushi Stainless Bottle SJ-TG10XA, Stanley Classic Insulated Thermos, and Stanley Adventure To Go) performed significantly better than bottles that had a lid with a handle over longer periods. The air gap between the cup lid and screw-in stopper might not be a vacuum, but it does help keep the thermos from losing heat through the top. 

Handled Lids Were More Convenient

Even though they didn’t perform as well in heat retention, thermoses with a handle on the lid were more convenient for everyday use. It was easy to snag the Miir, YETI, and Otterbox thermoses from the counter as we ran out the door, and you could even hook a carabiner through the handle to attach them to a bag. We also felt like their design was more versatile for people who plan on carrying cold liquids as much as hot—their wider mouths were easier to fill and drink from directly, so if you’re in the market for a water bottle that can double as a coffee carrier, this style might be more up your alley. 

Most Were Durable Enough For Everyday Use

While every thermos took some damage in our drop tests, all of them survived with slight dents and no impact on their leak-free status. Stainless steel corners took the heaviest impact, so the plastic bumper around the base of the Zojirushi Stainless Bottle SJ-TG10XA was a nice touch for softening impact. The drop test was another moment where the utility of the cup lid shone—by forming a protective barrier, the internal stopper was protected from impact. If you’re you’re accident-prone, a traditional cup lid thermos might be a better option. 

Usability Was Key 

Since every thermos performed well, usability features were important for picking our winners. We really liked the small wings on the Zojirushi’s cup lid, which gave us extra leverage for screwing it on and off, and the detachable lanyard on the other Zojirushi model was convenient for carrying. While the Otterbox thermos had a wide mouth that was easy to fill, it was so wide that it became precarious to pour from. That’s where the Miir bottle shone—even though it had a wider mouth than most, the bottle tapers towards the lip which slows down the flow and makes it easier to pour. 

The Criteria: What to Look for in a Thermos

Above all else, a great thermos needs to have excellent heat and cold retention. They also should be convenient to use and durable enough to hold up to everyday use.

Our Favorite Thermoses

The Best Thermos

Zojirushi Stainless Bottle SJ-JS10

View On Amazon $34 View On Zojirushi.com

What we liked: This slim thermos had excellent hot and cold retention, despite being significantly smaller than most of the competition. Its interior has a nonstick coating to prevent coffee oils from staining the inside, and its pour-through lid has a flip-up stopper mechanism that is easy to use and leakproof. We liked the fun pattern, but it also comes in plain stainless steel if you’re looking for something less flashy. All in all, its smaller size makes it easy to pack without sacrificing capacity or performance, and the small details on this thermos (like the tiny wings on the lid for better screw-on leverage) make it convenient for everyday use. 

What we didn’t like: It had a very narrow opening, so pouring hot liquids into it felt precarious.

Key Specs

• Weight: 13.8 ounces
• Materials: Stainless steel, plastic
• Product dimensions: 11.5 x 3.5 inches
• Capacities available: 1 liter
• Manufacturer temperature ratings: Hot: 180ºF at 6 hrs / 144ºF at 24 hrs, cold 45ºF at 6 hours
• Lid type: Cup lid
• Care instructions: Handwash only

Another Classic Thermos

Stanley Classic Vacuum Insulated Bottle

View On Amazon $39

What we liked: This thermos performed great in our hot and cold retention tests, held up really well to our drop tests, and was one of the lighter traditional thermoses we tested. We also liked its slightly slimmer body, which made it easier to grab and pour than other traditional thermoses. If you’re looking for a classic, heavy-duty thermos that’s easier to carry around, the Stanley Legendary Classic fits the bill. 

What we didn’t like: Its rugged build makes it great for camping, but its overall size might feel clunky compared to our top pick. 

Key Specs

• Weight: 22.5 ounces
• Materials: Stainless steel, plastic
• Product dimensions: 12.5 x 3.75 inches
• Capacities available: 20 ounces, 1 quart, 1.5 quarts, 2 quarts, 2.5 quarts
• Manufacturer temperature ratings: Hot for 24 hours, cold for 24 hours, iced for 5 days
• Lid type: Cup lid
• Care instructions: Handwash only

The Best Portable Thermos

Zojirushi Stainless Bottle SJ-TG08/10

View On Amazon $41 View On Zojirushi.com

What we liked: Another slim thermos from Zojirushi, this model matched our top pick for hot and cold retention but comes with a detachable lanyard for easy carrying. It’s slightly shorter than our top pick, making it easier to fit into tote bags, and sports the same flip-up lid and nonstick coating, to boot. It also had a plastic bumper around the base that protected it during our drop tests. 

What we didn’t like: It has a very narrow opening that made it tricky to fill with hot liquids and the knobs that the lanyard attaches to stick out and can get caught on things. 

Key Specs

• Weight: 13.8 ounces
• Materials: Stainless steel, plastic
• Product dimensions: 11.5 x 3.5 inches
• Capacities available: 1 liter
• Manufacturer temperature ratings: Hot: 180ºF at 6 hrs / 144ºF at 24 hrs, cold 45ºF at 6 hours
• Lid type: Cup lid
• Care instructions: Handwash only

The Best Wide Mouth Thermos

MiiR Wide Mouth Water Bottle

View On Amazon $40

What we liked: The Miir’s wider mouth made it easy to fill with both hot and cold liquids, and its slightly tapered shoulders made it easy to pour from, too. We loved the convenience of its handled lid and it performed nearly as well as our top picks for both hot and cold retention. It’s also one of the slimmer and lighter models we tested. This was the easiest bottle to drink directly from in our testing, so if you’re looking for a great everyday water bottle that can pull double duty for hot drinks, we think this is the thermos to buy. 

What we didn’t like: Its heat retention dropped off after eight hours compared to our other winners, though we think that’s more than enough time for most people. And while its handled lid is convenient, it’s more prone to damage after repeated drops compared to a cup lid. 

Key Specs

• Weight: 15.6 ounces
• Materials: Stainless steel, plastic
• Product dimensions: 11 x 3.5 inches
• Capacities available: 16 ounces, 20 ounces, 32 ounces 
• Manufacturer temperature ratings: None given
• Lid type: Handle lid
• Care instructions: Handwash only

The Competition

• Stanley Classic Insulated Thermos: This thermos also performed well in our temperature tests but its plastic handle was clunky and the other Stanley models looked more sleek and modern. 
• YETI Rambler 36oz: The YETI Rambler performed the poorest in our heat retention test, and we struggled to screw on the lid with hot liquids inside due to its dual lid system. We do recommend it for cold drinks, however. 
• Otterbox Elevation Growler: The extra-wide mouth on this thermos made it easier to clean, but it was difficult to pour from. 
• Stanley Adventure To Go: This model from Stanley has a sleeker look, but it didn’t perform as well as the other Stanley models in our hot and cold retention tests. 
• Swell 40z. Onyx Roamer: This thermos also had poor heat and cold retention and was bulky, heavy, and therefore hard to carry.
• Hydro Flask 32 oz Wide Mouth with Straw Lid: While this model was easy to drink from (with a flip-spout), it had poor heat and cold retention.
• Thermos Stainless King Beverage Bottle: This thermos had excellent heat and cold retention and performed incredibly well…until it got to the durability test. After it was dropped, it dented so much that it leaked and its lid would no longer unscrew from the base. That said, if you don't plan on dropping it, at just $21, it's a solid model for the price.
• Stanley QuadVac Bottle: A former top pick from our last round of testing, this model also was our top performer this time around. Unfortunately, it was discontinued before this review was published. 

FAQs

Are thermoses dishwasher safe? 

Some thermoses are dishwasher safe, but we still recommend handwashing them. Because more thermoses are tall and narrow, it’s difficult for a dishwasher’s sprayer to reach the entire depth of the bottle. Instead, we recommend getting a bottle brush in order to give your thermos a good scrub. 

What’s the best way to keep a thermos hot? 

While all of the models we tested performed well with pouring hot water directly into a room temperature thermos, you can preheat your thermos with a little boiling water and let it sit for a minute before dumping it out and filling it with your hot beverage of choice. This keeps your drink from losing thermal energy by raising the temperature inside the thermos and will keep your thermos hotter for longer.

What’s the difference between a tumbler and a thermos?

The biggest difference between a tumbler and a thermos is that thermoses tend to have a screw-in stopper lid (that sometimes doubles as a cup) for extra heat retention and leak-proofing. They also are usually larger and are designed for carrying enough liquid for sharing, while tumblers are generally designed for a single serving and have a lid you can drink from.  

What thermos fits in a car's cupholder?

Because a thermos is designed to hold a very large amount of liquid, all of our favorites are too wide to fit in a car's cupholder. If this is of importance, look at travel mugs instead. (All of our favorite travel mugs can fit in a car's cupholder.)

Why We’re the Experts

• Jesse Raub was Serious Eats' commerce writer and spent over 15 years working in the specialty coffee industry. He was our in-house coffee expert and regularly tests coffee and baking gear, including reviews of loaf pans, pourover coffee makers, and bread lames.  
• For this review, he tested nine thermoses by measuring hot and cold retention, usability, and durability. 
• The Zojirushi Stainless Bottle SJ-JS10RA and Zojirushi Stainless Bottle SJ-TG10XA are two longtime favorites that were our top picks when we first tested thermoses in 2022. They were retested again against previous picks and newer models and still came out on top.