Received a Yeti 20oz tumbler as a gift a few weeks ago. Since there was a Zojirushi 16oz and a dozen or so generic 12oz "tumblers" in the cabinets, I had to run a comparison test.
Here are the contestants:

I poured 202 degree water (from the same pot full) into all three tumblers, waited five minutes, and checked the temps. The Zojirushi had dropped to 194 degrees, the Yeti to 191 degrees, and the generic to 188 degrees in those first five minutes. First conclusion was that pre-warming (or cooling) the tumblers isn't such a bad idea. Geez, you just spent $30 on an efficient tumbler and lost ~10 degrees on fill-up.
Recorded temps through out the day to obtain this graph:

It's obvious that the Yeti is much better than the generic tumblers that most of us have been using. The Zojirushi really stood out as a high performer. The lack of an insulated lid is probably the primary contributor towards the Yeti coming in second.
I wondered what the data meant relative to real-world usage. My coffee pot turns out 183 degree coffee and the hot plate (on high setting) will warm it to 193 degrees after an hour or so. Sounds like 180 degrees is a reasonable high temp figure for a cup of coffee ... 140 degrees, although hot, seems to be the temp when I start towards the microwave.
So the curves were manipulated to produce this graph where the tumbler data starts out at 180 degrees and the time to cool to 140 degrees is easy to see:

If you start out with a tumbler of 180 degree coffee and don't drink it, then the generic tumbler will keep it drinkable for 1.2 hrs, the Yeti for 2.9 hrs, and the Jojirushi for 11.5 hrs. The Zojirushi might look like a yuppie toy, but it's really a good product.
The time frame for the Zojirushi matches what I've experienced using it ... fill it, leave it in the Jeep, and it's still good to drink on the way home after work. Its high efficiency is probably its greatest deficit for average use. If you start with too-hot-to-drink coffee, it simply doesn't cool down in a reasonable length of time. If you want to drink it now, then you've got to put drinkable coffee in it to start with. It's most forgiving when using it for cold drinks ... just not during summers in the South where a gallon an hour seems about the correct liquid intake.
The Yeti looks like it's well worth double the cost of the generic tumblers. An insulated closable lid would improve it's heat transfer efficiency, but I really like the convenience of the lid as designed. The sliding pieces on the generic caps get gummed up and are hard to keep clean. The Yeti is easy to clean ... and, easy to see where to clean since it's clear. Although the Zojirushi lid works well and can be cleaned completely, it is composed of two pliable seals and two hard plastic parts.
Looking forward to taking a road trip with the Yeti ...
Washington, IL > Queen Creek, AZ ... Two large eggs and an
adopted Mini Max
Comments
See der Rabbits, Iowa
I'm so old I recall when Zojirushi was only a bread-making machine.
It amazes me, how many people do not realize how the future works.
XXL BGE, Karebecue, Klose BYC, Chargiller Akorn Kamado, Weber Smokey Mountain, Grand Turbo gasser, Weber Smoky Joe, and the wheelbarrow that my grandfather used to cook steaks from his cattle
San Antonio, TX
Washington, IL > Queen Creek, AZ ... Two large eggs and an adopted Mini Max
Washington, IL > Queen Creek, AZ ... Two large eggs and an adopted Mini Max
@lousubcap ... that's funny about the bread maker, since they make some great rice makers in Japan - high end models that they don't export. Next time you're getting a cup of coffee from the containers at a hotel, look at the maker ... it's probably a Zojirushi product.
Washington, IL > Queen Creek, AZ ... Two large eggs and an adopted Mini Max
Washington, IL > Queen Creek, AZ ... Two large eggs and an adopted Mini Max
Location- Just "this side" of Biloxi, Ms.
Status- Standing by.
Agree on the requests to do a "cold" test.
re: Yeti vs Zoji, beyond the results
I think the differences in the lid create different use cases for each.
I keep the Yeti 30oz next with me all day to drink from while at home, whereas I would not choose to do that with the Zojirushi because of the extra lid manipulation needed. Plus, I already have a "home for lost gaskets" (seals) in a small jar. (When I wash something with a gasket, I remove the gasket before putting it in the dishwasher.)
Before the Yeti, my favorite to take with me on errand trips was the Contigo model, specifically because its the only model that does NOT have a gasket to lose. I keep the Contigo in my freezer. (fyi - YETI's are not supposed to be kept in the freezer from something I read here.)
In a car, the Yeti lid is spill resistant but not spill proof like the Zoji is. It does have a gasket, but it can't be removed / lost.
However, before I purchased the Yeti, I was in the market for something exactly like the Zoji, specifically for the "in the car" scenario. But unless I turn the Yeti sideways, that lid + a bendy straw is good enough to prevent most tilt spills in the car.
I do like my Zo though.
BTW, if you can't drink your coffee when first brewed, you're brewing it too hot.
I hate it when I go to the kitchen for food and all I find are ingredients!
MichaelDitto! And who doesnt love a rendition of Twinkle Twinkle Little Star when your rice is done (As my Zoji plays lol)
@stv8r Ok - confession time.
I've had mine for just over 10 years. I use it at least once per week, often more. That means I've heard that cute little jingle over 600 times - not until you posted did I realize it was Twinkle Twinkle Little star.
I would like to see the test done with no lids.
See der Rabbits, Iowa
You asked to see the test done with no lids. What's your guess as to the results?
Playing around with my Flameboss 200. Not sure they intended it for that use, but it makes an interesting data acquisition unit. With one food probe, I'm restricted to a single channel. Should be done testing late tonight.
Washington, IL > Queen Creek, AZ ... Two large eggs and an adopted Mini Max
A better test of insulation would be to submerge them in ice water to pre-cool, then pour 32F water in them and see how long they take to get up to some temp, like 60F. Heat rises so you have a lot of loss on the top. Hence the winner having the best top. But cold air sinks and the winner will be decided by the insulation quality of the sides and bottom.