Hydro Flask vs Thermos

Whether you just like to stay hydrated or you’re always on the go, having an insulated, stainless steel bottle provides you with an easy way to keep your drinks cold and keep track of your water intake.

These kinds of bottles are now more popular than ever, and lots of people are choosing insulated steel bottles over simple plastic ones. 

And when it comes to these bottles, there are dozens of different companies that manufacture them, and choosing which brand to go with can be quite challenging.

Among the most renowned ones are Hydro Flask and Thermos – both brands have millions of loyal followers and are well-known for the quality of their products. 

But which one of them is better? Should you go for a Hydro Flask or a Thermos bottle?

In this article, I’ll be taking a closer look at the two most popular products made by these companies – keep reading to find out how they compare to each other. 

Hydro Flask vs Thermos – A Product Overview 

Hydro Flask 

Even though it was founded only a bit over a decade ago, in 2009, Hydro Flask has managed to establish itself as one of the most important names in the drinkware industry.

Their bottles are particularly popular with the younger population, due to their stylish, eye-catching design. 

However, that doesn’t mean that HF’s bottles only look good – they are also highly practical, functional, and versatile. All of the company’s insulated bottles effortlessly maintain the temperature of hot and cold drinks.

They are also often equipped with convenient features, such as leak-proof flex caps, that make them much more convenient and easier to use. 

Hydro Flask Wide Mouth Stainless Steel Bottle

Hydro Flask flex-cap bottle


  • Weight: 15.2 ounces
  • Material: Stainless steel 
  • Insulation: TempShield insulation  
  • Sizes Available: 4 
  • Colors Available: 10 

Out of all the insulated stainless steel bottles offered by Hydro Flask, this one is the most popular, and for a couple of good reasons.

Besides the fact that it’s available in several different sizes and (chic) colors, the model offers superb insulation and sports a clean, sweat-free design. It has everything that outdoor enthusiasts need to keep themselves hydrated in the backcountry.


  • Simple yet versatile design 
  • Eye-catching colors 
  • Easy to clean 


  • Flimsy retaining strap 


This brand is much older than its rival – its roots go all the way back to the beginning of the 20th century when it was founded as Thermos GmbH by Gustav Robert Paalen, Albert Aschenbrenner, and Reinhold Burger in the German Empire. 

Over the years, the brand has expanded significantly and become extremely popular during the 1950s, when it sold over 2 million units.

The original company in Germany, as well as the branches operating in Australia, Canada, Japan, and the UK, were all acquired by the Japanese-based multinational corporation called Nippon Sanso K.K, in 1989. 

Thermos Stainless King Vacuum Insulated Bottle

Thermos bottle


  • Weight: 12 ounces
  • Material: Stainless steel
  • Insulation: Vacuum insulation 
  • Sizes Available: 1
  • Colors Available: 11

There’s a lot to like about this 40 oz vacuum-insulated bottle.

Advertised by its manufacturer as the “go-to piece of drinkware for outdoor enthusiasts and family campers”, it’s a model that effortlessly maintains the temperature of drinks for hours on end, and, while doing so, it doesn’t form condensation or become hot to touch.

And its lid doubles as a drinking cup!


  • Keeps hot drinks hot for longer 
  • More affordable than its rival 
  • Lots of convenient features 


  • The potential appearance of rust spots 

Hydro Flask vs Thermos – The Comparison 

The Insulation

Hiker holding a black Hydro Flask

The biggest advantage this type of drinkware has over plastic bottles is definitely the insulation. In the case of Hydro Flask, the company uses something called the TempShield technology, which, truth be told, isn’t that different from your standard double-walled vacuum insulation. But it does its job pretty well – there’s no doubt about that. 

If you fill this Hydro Flask bottle with ice and leave it sitting, the ice will start to melt only after about 24 hours. This is seriously impressive and something that’s bound to be of huge help during long summer hikes.

What is more, the ice-cold water inside the Hydro Flask bottle won’t make it sweat, and that’s always a huge plus in my book. 

Hydro Flask claims that their bottle can keep hot drinks hot for about 12 hours, but you can be sure that your hot tea will turn into lukewarm tea after only 6 hours inside this bottle. Thermos, on the other hand, claims that their bottle can maintain the temperature of both cold and hot drinks for about 24 hours.  

And while the model is capable of keeping cold drinks cold for a long time, it can maintain the temperature of hot drinks for only about 8 hours (and sometimes even longer).

That’s at least two hours longer than in the case of Hydro Flask’s model, which gives the Thermos bottle the title of the winner in the insulation department.

In the realm of Hydro Flask vs Stanley, Stanley’s bottles, much like Thermos, often emphasize their long-standing reputation for durability and insulation. While Hydro Flask boasts modern aesthetics and TempShield technology, Stanley’s classic designs have been trusted by many for maintaining drink temperatures during extended outdoor adventures. It’s a close contest, with both brands having their unique strengths in the insulation game.

Similarly, when considering Hydrapeak vs Hydro Flask, the former is often recognized for its competitive pricing and varied designs, while the latter continues to be a favorite for its innovative insulation techniques.

The Construction Quality

Feeling substantial in hands and being made out of stainless steel, the Hydro Flask bottle is certainly a durable piece of drinkware.

However, due to its girth, the model becomes quite heavy when it’s full and therefore impacts the floor with a lot more force. This means that the dents are sometimes unavoidable, especially if you accidentally drop your Hydro Flask bottle onto the rocky ground. 

One thing a lot of people complained about is how flimsy the cap of the Hydro Flask Wide Mouth Stainless Steel Bottle can be.

And while this is true, having a bad-quality cap replaced is quick and free – you only have to fill out a user-friendly warranty claim on the company’s website and they will send you a new cap immediately and at no charge. Hydro Flask’s customer service is, without a shadow of a doubt, one of the best in the industry. 

What about the construction quality of the Thermos Stainless King Vacuum Insulated Bottle? As its name suggests, this bottle is also made out of stainless steel and therefore easily withstands daily wear and tear.

During my drop test, the model ended up with only a small scrape after I dropped it while it was full from a height of about two meters. 

One important thing to mention here is that quite a few users reported that they noticed spots of rust on the interiors of their Thermos bottles.

While I didn’t experience anything like this while testing the model, it’s certainly something that raises serious concern. But still, I think this can be easily avoided by regularly cleaning and drying the bottle.  

The Ease of Use

Hydro flask bottles in an outdoor environment

Due to its fairly simple design, the Hydro Flask model is an extremely easy-to-use water bottle. My only complaint in this regard is that the model’s retaining strap isn’t of the best quality. While it can be used to clip the bottle to a backpack, that’s not something you should do when the bottle is full and you’re moving a lot. 

The Thermos bottle is even easier to use and it’s definitely a winner in this department. Not only does it come with a built-in carry handle that allows quick and easy use, but it’s also equipped with a twist & pour stopper, which allows the owner to pour the drink without completely removing this part of the bottle.

Moreover, the model’s lid doubles as a serving cup – how handy is that? 

The Ease of Cleaning 

As it consists of only two simple parts – the bottle and the cap – this Hydro Flask model is exceptionally easy to clean. I found that it takes only a minute to clean the entire thing with the help of a brush.

While it’s true that the Hydro Flask Wide Mouth Stainless Steel Bottle is a dishwasher-safe model, the manufacturer advises against washing the bottle in the machine – doing that can have a negative effect on its insulation. 

The same can be said for the Thermos bottle – it is dishwasher-safe, but cleaning it by hand is always a much wiser decision. And due to the fact that it has more parts than its rival, cleaning it is a bit more time-consuming and difficult. 

And due to the user reports about rust spots appearing on the inside of this bottle when it’s full but not used for days, manual cleaning is something you’ll have to do more frequently than in the case of the Hydro Flask bottle. 

The Best Application

Hydro Flask on a green bench

Both of these bottles can keep cold drinks cold for a long time, which makes them perfect for office use. However, their volume (40 oz, although the Hydro Flask model is also available in 64 oz, 32 oz, and 20 oz variants) is sufficiently large to last you one full gym session without having to refill them constantly. 

Now that we know that both bottles have advantages in the urban environment, an important question arises – which one of them is better for backcountry use? In my opinion, that would be the Thermos Stainless King Vacuum Insulated Bottle.

Not only does it keep hot drinks hot for longer, but also comes with a couple of very useful features – like the twist & pour function or the lid that can be used as a cup – that make it more convenient for use in the Great Outdoors. 

Hydro Flask vs Thermos – The Verdict

Hydro Flask lying on the ground

So, at the end, who’s the winner of this battle? The fact that some users have reported the appearance of rust spots on the insides of their Thermos bottles raises serious concern.

However, if you’re someone who takes proper care of his drinkware and washes it often, that is not something you’ll need to worry about. 

Due to its ability to maintain the temperature of hot beverages for longer, as well as the fact that it comes with some practical quality-of-life features, the Thermos Stainless King Vacuum Insulated Bottle stands as a better choice – just make sure to wash it properly and frequently. 

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