Which Thermos Bottle Keeps Your Water Hot the Longest?

Testing 8 different bottles to discover which is the hottest thermos bottle out there.

Any outdoorsy person knows that choosing the right water bottle for the adventure matters.  I personally have an entire cabinet dedicated to all sorts of bottles, thermoses and the like. Google search “best water bottle”and you’ll get hits from thousands of websites including Outside Online, Outdoor Gear Lab, Popular Mechanics and so many more!  

The problem is none of the reviews that I’ve found actually quantify “best” in way in the way I was looking for. Being that my day job is a test engineer at a certified lab I decided to take on the challenge.  

For our Denali trip I decided that the most important quality I was “how long will my bottle keep boiling water hot?” Denali is a cold place and I wanted to know that my water wouldn’t freeze instantly and that I could warm my belly with hot tea and electrolytes hours into each day’s climb.

In the end I quantified the results based on how warm the boiling water was after 7 hours in a zero degree Fahrenheit freezer.  Below you’ll see exactly what bottle stayed the warmest and how warm, you’ll get my personal opinion on each bottle and what I liked and disliked about them on trips that they have helped quench my thirst on.  



Each bottle was filled with boiling water (210-212F) to the fill line. Then sat at room temperature (68F) for 30 minutes. Bottles were then placed in 0F and temperatures were recorded at 4 hours and 7 hours. Bottles were only opened at 4 and 7 hour mark to record temperature.
4 CAMELBAK CHUTE 1.2 153.3 133.4 16 38
5 HYDROFLASK WIDE MOUTH BOTTLE 1 149.3 128.1 14.1 40
7 CAMELBAK CHUTE 0.6 128 104.6 10.9 28


Opinions and Observations


This vacuum sealed stainless steel bottle was the winner of my test keeping its contents to a still super warm temperature of 166 degrees after 7 hours in the zero degree freezer. It’s a bottle that you don’t drink directly out of but do so using the integrated insulated cup that screws over the pour through top.  

Although the bottle is bigger in size it was absolutely worth stuffing into my pack for the few weeks on Denali. It’s easy to use, seals very well and kept my tea and coffee warm literally all day, there were multiple times I was pleasantly surprised that my drink was still steaming much later in the day (or night). I would even fill this with boiling water at dinner time and and drink it after waking up to warm me up and get me going.

The bottle did not retain any flavors, it pours without dripping and even the cup is insulated and stays warm while you sip.  Plus it comes in a bunch of cool colors, including my favorite, green!

Bottle Line: The 1 liter Glacier bottle kept beverages the warmest out of all the bottles I tested, although a bit larger and pricier, this will bottle will make its way into my pack for any overnight winter trek I go on.

STEELWORKS BY SIGG THERMOS, 1 Liter (discontinued)

While completing this write up I unfortunately found out that this product is discontinued, although that’s the case I’m still going to go through the details. This bottle came in second in my test finishing up at a respectable 159 degrees.  

With the pour through spout and integrated cup this is a great bottle for car camping or any trip where you want your beverages to stay hot.  I’ve filled this with hot coco (read:coco and whiskey!) plenty of times and kept it in the lodge while riding at the resort.  

Bottle Line: A nice bottle that keeps beverages warm for hours with slightly less bulk, if this sounds like the bottle for you, then maybe try out their Classic Thermo 1L water bottle. I haven’t used it, but it seems to have filled the Steelworks’ spot in their lineup.


The baby brother of the GSI Glacier bottle that won first in my review.  The only difference here is that it’s got half the volume coming in at half a liter.  This thing is great for a chilly day hike where you know you’ll want a warm pick me up on top of your summit.  It fits into most pack bottle holders and keeps your drink warm  (or cold on summer days) for hours.  

Bottle Line: The half liter Glacier bottle is much smaller and more manageable than its 1 liter bro so it’s great for day hikes when the temperature of your drink is just as important as the trail you’re hiking.  

CAMELBAK CHUTE, 1.2 Liter ($38)

The Chute is a pretty awesome bottle. It’s insulated and kept the water to 133 degrees, right in the middle of the tested bottles, but what I like about it is that it’s easy to drink out of. It has a tiny spout that can easily be unscrewed for drinking but the entire cap unscrews for filling and cleaning.

The only downside I see to this is that with two sets of threads there is a greater possibility for leakage.  Its also a large bottle and because of that, heavy. Despite this I find myself using this bottle more and more each week because of its easy drinkability while walking, hiking and driving as well as its large capacity. It holds the most liquid out of any of the bottles that I tested at 1.2 liters and I drink a lot.  

Bottle Line: Quickly becoming the bottle I carry everyday. I love the large capacity and the easy drink spout. Despite being a little bulky I like it and love the texture color, stainless steel look.


I’ve been using this almost daily since my fiancée got it for my birthday over a year ago. It’s been great for keeping drinks hot and cold for quite a long time (128F in my test). I love that it’s simple and sleek, plus it comes in basically any color you could want. The wide mouth makes it easy to clean and just as easy to toss some ice in on a hot day.

The few flaws I can think of are that it’s on the heavier side for a regularly insulated bottle, if you do fill it with piping hot water be careful as the lip is stainless steel and I unfortunately did chip the paint on the bottle of mine.

Bottle Line: Although it’s the most expensive bottle on my list I love it. I’ll continue to use it throughout the year and I’m sure it will make it into the pack for many more trips.  


Another gift from the fiancée, I guess she wants to keep me well hydrated! This is my go to with loose tea which I drink on the go at least once a week.

I love it because it has a removable tea infuser that I can fill with my favorite mixes. Its also great because it has a quick press button top for drinking, no unscrewing necessary. Only downside is that it’s tough to clean with its medium diameter mouth and the interior becomes stained, although it does not seem to retain any leftover flavors.

Bottle Line: If you drink loose tea this is the bottle for you, it’s great on the go and keeps the beverage hot for hours.  

CAMELBAK CHUTE, 0.6 Liter ($28)

The smaller sized Chute. It has all of the same great features as the larger version but compacted to half the volume. Great for smaller trips or times when you don’t expect to drink as much.

This bottle was great on Denali although it didn’t keep our water the warmest it was nice to clip to our harnesses via a carabiner for easy access to water. Because it is double walled, it stood up to the frigid weather and its smaller size did not get in the way while swinging from our sides.  

Bottle Line: Another great easy drinker.  This bottle proved itself on Denali and will always be in the wheelhouse from now on.  

WIDE MOUTH NALGENE WITH FORTY BELOW BOTTLE BOOT, 1 Liter ($10 bottle, $25 Bottle Boot)

No hiker can deny the time tested awesomeness that is a standard Wide Mouth Nalgene. This bottle comes on every trip with me and gets used way too often. After literally years of use it’s held up just fine and has no weird flavors. The wide mouth makes it easy to clean and refill.

This is the only plastic and only non insulated bottle I tested but when you add the 40 Below Bottle Boot now you’re set! You have a super lightweight, compact and bare bones bottle that’s perfect for stuffing in the backpack. The Bottle Boot keeps the water just warm enough not to freeze for over 7 hours at 0 degrees.

On Denali one thing I wish I bought was the Bottle Boot for my 1.5 liter Nalgene. This insulating cover made all the difference. Not only that but it has a nice loop on it that I would place on my pack’s sternum strap for easy sipping on the go.

Bottle Line: The cheapest bottle tested matched with a great product from 40 Below gives you a super versatile light weight option for any situation you can dish out. This bottle will be around forever and the 40 Below Bottle Boot should be on it in any cold conditions, PERIOD.


Which is the hottest thermos bottle out there? Or at least in my current arsenal?

In this test, the GSI Vacuum 1L Bottle came out on top keeping water the hottest and earned its place on Denali with me. Well, so did a couple of the others, but the GSI was my go-to for really keeping beverages hot during days on the glacier and for knowing I could fill go to sleep and still wake up to hot tea.

Eight solid bottles were tested at the lab and one of the biggest factors I noticed in the double walled bottles were the caps. Hypothetically speaking if the wall thickness of each tested was the same then the cap would make the greatest difference in heat retention and without knowing for sure I would expect this to be true in my testing.

Looking at the bottles in order you can see that the three thermos style bottles came out on top followed by the others with a more standard thinner cap. Although there are plenty of other brands I would have liked to add to this comparison I don’t have those ones in the cabinet right now and probably won’t for a while. If get them them I will make sure to update this!

Heat retention aside, the weight, size, style and cost all play into what you’re going to buy and use. Just make sure you pick the right bottle for the adventure!

Ryan Sarka
Ryan Sarka

Brand Ambassador & Writer

Cyclist, climber, snowboard mountaineer, triathlete, and engineer. Founding member of Between The Peaks. Bikepacked across the entire U.S.

  1. This is the best article I have seen as a review / comparison of these products . Quantified analysis makes much more sense for me compared to other reviews. Thanks for the job well done!

  2. In your test you didn’t specify whether you pre-heated the containers, as is usually recommended. The first step should have been to fill the container with boiling water, wait at least a minute, then discard this water before testing as described. This would definitely effect outcomes, since an inner wall with a greater mass would absorb more of this initial heat and outperform a thinner wall even if the insulating properties were identical.

    1. Good tip Kenneth, thanks! I’m pretty Ryan didn’t do that before testing… so maybe the hours that the water stayed hot would have been extended if the bottles had pre-absorbed some heat, that makes sense. But having not pre-heated any bottle, the test is still consistent across the board. I can’t say I’ve heard of that trick, and will definitely give it a go, but we were testing these bottles to see which would be best to bring to Denali where we wouldn’t have the luxury of discarding any water at all when it takes hours to gather melt and boil snow after a long haul to a cache or camp.

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