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Hydro Flask vs. Thermoflask Review: The In-depth Review and Comparison

Portable drinking bottles are lifesavers. Literally! Not only do they make it so that you always have a fresh source of water wherever you go, they are designed with vacuum seal technology so you can have piping hot drinks, or ice cold drinks. A quick google search will tell you all the benefits you gain from proper hydration, and these bottles make it that much easier to get in your 8 glasses of water per day.

Those that work the 9 to 5 can use them to transport their morning cup(s) of coffee from home to the office, maximizing their time and saving money by skipping the Starbucks drive-thru, while gym rats, runners, hikers, and adventure seekers will have something to provide them the proper hydration for their active lifestyles.

This article takes an in-depth look at two models that should be on everyone’s radar – the best-selling Hydro Flask, and the up and coming Thermoflask. Both are excellent choices and provide a lot of value for consumers from their high-quality construction to their multi-hour temperature retention.

But what are the differences? Which ones holds more drink? How much do they cost? Is one far superior to the other?

We answer those questions and more as we break it all down for you.

Hydro Flask vs. Thermoflask

Hydro Flask Review

The Hydro Flask is the original, king of portable water bottles, and with good reason. It is a well-performing bottle that keeps hot drinks hot, and cold drinks cold, and at the end of the day, that’s all we are looking for with these types of portable drink holders.

Available in multiple sizes – 18 oz., 21, and 24 – the 18 oz. bottle weighs 11.3 oz., with dimensions of 8.7 x 2.87 inches. The mouth diameter of the flask is just shy of 2 inches at 1.91, giving you a wide opening for filling, sipping, and pouring. Each size will also fit a standard cup holder, which will come in handy as most people bring these to the gym and/or their workplace.

The bottle uses 18/8 stainless steel, and is also BPA and phthalate-free to ensure that the flask you are drinking from is not only eco-friendly, but has zero toxicity levels that could potentially compromise your immune system. The stainless steel is double-walled and vacuum sealed by removing the layer of air between the steel plates, providing superior insulation which keeps hot and cold temperatures locked in for extended amounts of time. Hydro Flask refers to this as their Tempshield system, which provides 24 hours of cold temperature retention, and 6 hours of hot. In addition, this vacuum seal also eliminates heat transference, so your hot drinks won’t heat up the outside of the bottle and burn your hand, while your cold drinks won’t warm up if the temperature outside is hot. This is important for keeping the bottle at a constant temperature, and reduces bottle sweat and condensation on the outside of the flask.

Aesthetically, the Hydro Flask comes in a wide range of color options, and is covered covered in a durable powered coating, which improves durability and longevity, protecting it from scratches and dings, while providing you a grippy material so it won’t slide out of your hand easily. NOTE: Only wash this bottle by hand with dish soap and warm water. Cleaning it in the dishwasher will strip away the outer coating due to high heat exposure and abrasive detergents.

Finally, we have the lid, which uses a honeycomb designed pattern for extra insulation, as well as a threaded gasket that makes it leakproof. A nice feature is that the threads on the lid protrude out, so it is very easy to clean, whereas most other lids are designed with opposite threading. On top of the lid is a flexible silicone handle that allows you to hold it comfortably, and also makes it easy to attach to a backpack using a carabiner.

If there is a downside to this bottle, it would be that the lid has to be fully unscrewed every time you want to take a sip of your beverage. Hydro Flask has a few variations of lid, with a straw design being a popular separate purchase, however, it is important to note that only the included flex cap is leakproof.

In addition to everything the Hydro Flask provides, you also get a lifetime warranty against manufacturer defects, making it a pretty safe purchase.

  • Best-Selling Water Bottle
  • Available in Multiple Sizes and Colors
  • Fits Most Cup Holders
  • Tempshield Double-Wall Insulation
  • Provides 24 Hours of Cold Temperature Retention, 6 Hours of Hot
  • 100% Leakproof Due to Flex Cap Lid
  • Durable Exterior Coating for Improved Grip and Scratch Reduction
  • Eco-Friendly Construction From Non-Toxic Materials
  • Lifetime Warranty Against Defects

  • Not Dishwasher Friendly
  • Lid Must Be Unscrewed and Removed Every Time You Drink

Thermoflask Review

The Thermoflask is the new kid on the block, but without a doubt, it is giving the Hydro Flask a run for its money. It has a very similar design to the Hydroflask, with excellent hot and cold temperature retentions, but also has a few differences.

With the 18 oz. model standing 9.2 x 3.2 inches, and weighing 11.5 oz., it fits the hand nicely, and its also available in 24 oz., 32, and 40 oz. sizes. With a slightly wider build than the Hydro Flask, the mouth opening allow more room for filling or drinking from, and the 18 oz. and 24 oz. models will both fit most cup holders. The larger sizes will need to be stored some other way.

Material-wise, the flask is crafted out of food-grade 18/8 stainless steel, eliminating flavor transfer (no metal taste), as well as rust and corrosion, and it is also BPA-free for a non-toxic drinking experience. A vacuum insulated seal with double plates of steel hold heat and cold in for long periods of time. Cold beverages can stay that way for 24 hours, while you’ll get 12 hours to drink your hot drinks before they start to lose warmth. Vacuum seals remove the layer of air between the stainless steel plates, trapping the ideal temperature inside the bottle while eliminating heat transference, and as a result, the exterior won’t sweat and will always be cool to the touch. This also works the other way, as cold beverages won’t be affected by your hand heat while you are holding the bottle.

Providing customers a few different colors to choose from, the exterior of the Thermoflask uses double powder coating for extended durability against scuffs and other superficial damage, while at the same time allowing for a firm grip that avoids slippage. As with most of these colored bottles, they should only be washed by hand to avoid exterior damage from the high heat and abrasive detergents that products are exposed to in dishwashers. Washing should be done before first use, and after every use to avoid waterborne bacteria from forming.

The lid on the Thermoflask uses a flip-style design that ensures there is no leakage from the spout, and a gasket ring at the fill-opening provides a similar airtight seal. The spout allows you to sip, chug, and pour from the bottle with ease, and a hinge lock keeps the lid out of the way so you aren’t fighting with it when you need to quench your thirst. There are also additional lids that can be purchased separately if you prefer a straw style or wide mouth opening. A silicone band around the base of the lid gives great grip, making it simple to twist the lid off when you need to fill or wash the bottle.

Topping off the features is a wide plastic handle so you can transport it anywhere with ease, and Thermoflask guarantees perfect workmanship by including a lifetime warranty for peace of mind purchasing.

  • Uses Food-Grade 18/8 Stainless Steel
  • Double-Wall Insulation for Excellent Temperature Retention
  • 12 Hours of Hot Drinks, 24 Hours of Cold
  • Multiple Sizes Available
  • Different Colors to Choose From
  • Spout Design and Silicon Gasket for Leakproof Lid
  • Double Powder Coated Exterior For Resilience Against Damage
  • BPA-Free and Non-Toxic
  • Lifetime Warranty Against Defects

  • Not Dishwasher Friendly

The Differences: Hydro Flask vs. Thermoflask

Now that you have a good overview of the two bottles, what are the key differences?

  1. The Thermoflask is slightly taller and thicker. When comparing the 18 oz. size bottles, while the height may not make much of a difference, the slightly wider opening can make refilling the flask easier, and will make the addition of ice cubes a non-issue.
  2. The Thermoflask is available in more sizes, and larger sizes – 18, 24, 32, and 40 oz., while the Hydro Flask comes in 18, 21 and 24 oz. sizes.
  3. The spout lid on the Thermoflask allows you to drink straight from the top simply by popping it open, while the lid that comes with the Hydro Flask acts like more of a stopper and needs to be fully removed off the bottle every time you want a drink.
  4. The Hydro Flask has better long term temperature retention. Two studies were carried out on both bottles. The first experiment filled each bottle with hot liquid, and it was only after 24 hours (1 full day!) that the Hydro Flask pulled away as the winner, maintaining a slightly hotter temperature. The second experiment monitored the temperature levels during “regular use” by taking sips from each bottle throughout the day. It took 8 hours to see a temperature change, but once again, the Hydro Flask came out on top with a slightly more stable temperature.
  5. The Thermoflask costs almost 50% less than the Hydro Flask.


These two bottles are so close in terms of quality and features. The both excel at providing cold and hot beverages for long periods of time. For our money, we would say the Thermoflask is the winner. Being able to drink straight from the lid, a larger selection of sizes, virtually identical heat retention times (unless you are planning on waiting a full day before ingesting your drink), and costing nearly half the price of the Hydro Flask make it a no brainer. if you want to be diplomatic about it, you could get the Thermoflask for your day-to-day cold drinks, and a Hydro Flask for your non-hydration drinks, like coffee or hot chocolate. Best of both worlds!

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