Over time, I’ve amassed an embarrassingly large collection of vacuum insulated steel water bottles including YETI, Hydro Flask, S’well and Klean Kanteen. I’ve managed to delude myself into believing each bottle serves a specific purpose in my daily life (Marie Kondo would not approve). But one thing I’ve never tested is their insulation properties relative to each other. If you’re curious about which bottle holds heat the best – read on!
The Experiment: Which Insulated Bottle Holds Heat the Best?
left to right in photos
- YETI 20 oz Rambler with Lid
- Hydro Flask 24 oz with Flip Cap Note: 20 oz is the standard size – this particular 24 oz bottle is the REI Members special edition. Yep, I am a huge sucker for things like this.
- S’well 25 oz bottle in white marble
- Generic 17 oz steel tumbler (non-vacuum insulated)
- Klean Kanteen 12 oz Coffee Mug with Cafe Lid
The Set Up:
I used a very high tech tea kettle to boil water to about ~210 degrees Fahrenheit before filling up each bottle to capacity. Afterwards, I measured and noted the temperature at hours 0, 1, 2, 4, 6, 8 and 13. The bottles were left in the same room and location – room temperature stayed consistent at 68 degrees Fahrenheit.
- Size: I realize that this isn’t a true 1:1 comparison as the bottles had different volumes, which impacts effectiveness. If I were to re-do the experiment, I’d love to have all 20 oz bottles. For now, I filled them all up to capacity to test them as manufactured (vs filling up the S’well halfway, for example).
- Cap Format: As you can see in the photo below, each bottle had a different cap. I guessed that the YETI would not perform as well as Hydro Flask because of its plastic tumbler lid.
- Initial Temperature Drop: Water temperature dropped about ~10 degrees when transferring from the tea kettle to each of the bottles. Some bottles saw less of a change than others – for example, the YETI tumbler saw an 11 degree drop to 198 degrees while Hydro Flask saw a 7 degree drop to 203 degrees.
Of course, I tracked everything in a Google Sheets document..
And the winner is… S’well!
After 8 hours, water in the S’well bottle was a whopping 172 degrees – only a 30 degree drop from what it had started with. I was pleasantly surprised, as I purchased the S’well mainly for its aesthetic properties and for use with cold beverages. The strong performance is an added bonus. Out of curiosity, I left it overnight and measured again the next morning. The water was an impressive 130 degrees 22 hours later.
Does this mean it’s the best bottle overall? If you’re looking for something to keep a large amount of coffee, etc. hot for a long period of time (think: overnight trips), then yes. However, If you’re looking for a desk option and want to drink your coffee without burning your tongue – the YETI or Klean Kanteen may be a better choice.
- Interestingly enough, the 12oz Klean Kanteen was about on par with the 20oz YETI Rambler. It’s nice to know that the smaller kanteen can keep up with the rambler for drinks like coffee, where you may not need the extra volume.
- While the S’well bottle maintained heat better than the Hydro Flask did, I’ll probably continue to use the Hydro Flask for my hot beverages, which I typically drink immediately. It’s easy to splash liquid on yourself with the S’well bottle mouth (or, I’m really just very terrible at drinking) – and I wouldn’t to risk burning myself with scalding water.