How we tested
Whether it’s hot coffee for your commute, ice-cold water for your workout, or cool rosé for your leisurely picnic, travel mugs are ideal for keeping your favorite beverage at its proper temperature. It had been a while since we last tested these mugs, and we wanted to know if our former favorite, the Timolino Icon Vacuum Travel Tumbler, was still the best option available. So we bought eight models, priced from about $12 to about $33, including our previous winner. The market is glutted with travel mugs, so we narrowed our lineup using findings from previous testings. We decided to focus on insulated stainless-steel mugs, as we’ve found that they’re much better at retaining heat and cold than noninsulated plastic and ceramic mugs. Because most travel mugs are available in different sizes, we limited our lineup to models with capacities of about 16 ounces, the most common size, though we did include one popular model that came only in sizes of 20 ounces or more. We also chose models that could be operated with one hand, so you can safely drink from them while clutching a steering wheel or subway pole with the other hand. And we ruled out models with handles, as we’d found that these get in the way when the mugs are placed in car cup holders.
With our lineup solidified, we got to work, testing to see how well they retained heat and cold, how easy they were to open and close, and how durable they were—repeatedly dropping, washing, and opening and closing them. Finally, we sent additional copies home with users for a full month to see how they fared with more extensive use.
Heat and Cold Retention Are Critical
First and foremost, a good travel mug should keep your hot drinks hot and your cold drinks cold for a reasonable amount of time. Although opinions vary on the best temperature for hot coffee, we deemed coffee below 130 degrees Fahrenheit tepid and less pleasant to drink. Serving temperature aside, we also considered food safety. The U.S. Department of Agriculture’s Food Safety and Inspection Service doesn’t recommend drinking coffee and many other beverages if they’ve been in the danger zone (from 40 to 140 degrees Fahrenheit) for more than 2 hours, as bacteria can grow to a critical level after that point.
To evaluate how long the mugs could keep hot drinks at an acceptable serving temperature and still safe to drink, we poured coffee directly from the coffee maker carafe (a starting temperature of 174 degrees) into the mugs and tracked their temperatures over a full day. Happily, all the travel mugs were able to keep the coffee hot and safe to drink for at least 3.5 hours—plenty of time to commute to work. But some mugs performed even better; three models extended that time to 5 or 6 hours, and the coffee in one impressive model stayed hot and safe to drink for nearly 10.5 hours, dropping about 4 degrees an hour for the first 8 hours—about half the rate of most of its competitors.
The mugs were just as good at keeping cold drinks cold. It took almost 24 hours for cold coffee poured straight from the fridge (a starting temperature of 36 degrees) to come up to room temperature (68 degrees) in most of the travel mugs. Most models kept the cold coffee safe to drink for 3 to 4 hours—more than enough time for us to enjoy them. Here again, the overachieving mug from our first test proved stellar, keeping the coffee safe to drink for 6.5 hours and taking three full days to come up to room temperature.
Obviously, we don’t recommend trying to drink coffee after it’s been out for three days. Not only would you be risking your health, but the flavor would also have deteriorated. As we learned from Peter Giuliano, chief research officer for the Specialty Coffee Association, the flavor of hot coffee can suffer if it’s held for too long, as it undergoes chemical reactions that will make it more acidic over time. (These chemical reactions occur much more slowly with iced coffee.) Still, we preferred travel mugs that kept drinks hot or cold for longer periods, as they gave us more time to enjoy our favorite beverages at the best (and safest) temperatures.
Most of the Mugs Were Leakproof
Ultimately, it doesn’t matter how long a mug is able to keep a beverage hot or cold if it’s a pain to use. First, the good news: Almost all the mugs were completely leakproof, securely containing ice water even after we’d filled and dropped the mugs from counter height five times, opened and closed them 100 times, and washed them according to the manufacturers’ instructions 10 times. One model didn’t quite make it through with perfect marks, though. Unlike most travel mugs, which have tops that screw onto their bases to seal shut, this mug had a unique top that could be easily pushed into the base of the mug, sealing in the contents. While the rubber gasket that held the lid in place was surprisingly strong, maintaining its seal for most of the testing and proving otherwise leakproof, the lid still popped back off once when we dropped the full mug on the ground, allowing ice water to pour out. With this in mind, we preferred the screw-top models, as they sealed more tightly and never leaked.
Wide Mugs Are Easy to Fill but Hard to Open and Hold
The screw-top models had other problems, though. In many cases, it was a challenge just to get the tops off the mugs in order to pour in the drinks. Several of these screw-top mugs had wide openings measuring more than 2.5 inches across; while the wide openings gave us plenty of room when pouring in the drinks, they came with correspondingly wide tops that were harder for even larger hands to span, grip, and unscrew. Once off, these tops were just as hard to get back on, and not just because they were too wide for us to comfortably get our hands around: Many didn’t thread smoothly onto the base, requiring us to make several attempts to ensure that we’d closed the mugs securely. We much preferred screw-top mugs with narrower openings and smaller tops measuring about 2 inches in diameter; although we had to aim a bit more carefully when filling the mugs, we didn’t have to struggle quite as mightily to unscrew and screw on the tops. These smaller tops required less force to thread onto their bases, a benefit our science research editor thinks could be attributed to the fact that they have less surface area coming in contact with the base than larger tops do and thus generate less friction as they’re screwed on.
Mugs that were wide from top to bottom had additional disadvantages. They were awkward for even large hands to hold. And at least one model—the pop-top mug, which was both the widest of the bunch and the one with the largest capacity—didn’t fit in the back seat cup holders of one tester’s car. Slimmer, smaller-capacity models were easier to grip and fit effortlessly into backpacks, totes, and cup holders.
Enclosed Drinking Spouts and Intuitive Operation Are Best
When it came to drinking from the mugs, new problems emerged. We disliked models that had exposed drinking holes for sipping; even when the holes were closed off, they collected liquid and dust, making them less pleasant to drink from when they were open. Instead, we preferred models with drinking spouts that were entirely enclosed by hinged hoods, as they stayed cleaner.
The mechanisms used to open and close off the holes and spouts, however, were sometimes surprisingly unintuitive and hard to operate. Testers universally hated one model, which required them to press a button continuously in order to keep the drinking hole clear so that liquid could flow through it; the button itself was stiff and a pain to keep depressed. Another model had a lid that had to be twisted to expose the drinking hole, but because of the way the lid was designed, we often ended up twisting off the entire top. We much preferred mugs that had simple opening mechanisms; an effortless press of a button is all it takes to flip up the hood and expose the enclosed spout on our top two models.
We also liked mugs that had locking mechanisms because they prevented the lids from flying open by accident and spilling the drink into a bag or cup holder. Models that lacked this locking feature gave us pause; we’d think twice before throwing any of them haphazardly into a bag.
Notes on Odor Retention, Ease of Cleanup, and Durability
There are a few things you should be aware of if you’re interested in owning a stainless-steel travel mug. One is odor retention; all the models smelled of coffee even after we’d washed them 10 times, most likely because they all have silicone or rubber gaskets, which are notorious for holding on to odors. Moreover, most of the manufacturers recommend washing their mugs by hand in order to prevent the paint on the outside from fading or chipping; this was a deal breaker for a few of our testers, who wanted a mug that they could throw in the dishwasher instead. (If that’s also a priority for you, we did test one mug that was fully cleared for dishwasher use.) Because they’re made of metal, the mugs aren’t microwave-safe, so you can’t zap your coffee to make it hotter. And while these metal mugs are unlikely to break, they can certainly dent if you drop them, as we did five times; none of the eight models in our lineup escaped this test without a few scrapes, dings, and dents. Most testers found these issues to be minor; a little extra care was a small price to pay for the mugs’ excellent heat and cold retention.
The Best Insulated Travel Mug: The Zojirushi Stainless Mug (SM-SE)
In the end, we had a runaway new favorite. The Zojirushi Stainless Mug (SM-SE) was beloved by all who used it. It was far and away the best at maintaining beverage temperatures, keeping hot coffee hot and safe to drink for 10.5 hours and cold coffee cold and safe to drink for 6.5 hours. It was incredibly simple to use as well. One of the narrowest models we tested, it was comfortable for hands of all sizes to hold, and its top was easy to screw on and off. It’s easy and hygienic to sip from, too: A quick press of a button and the hood on the mug’s top pops open, exposing the drinking spout, which otherwise stays clean and debris-free. And it comes with a locking mechanism, so you’ll never spill your drink by accident.
- Test eight insulated, stainless-steel travel mugs, priced from about $12 to about $33, all with capacities from 16 to 20 ounces
- Check for leaks at the beginning and end of testing by filling each mug with water and turning it upside down five times
- Track each mug’s heat retention, using coffee poured straight from coffee maker carafe
- Track each mug’s cold retention, using cold coffee poured straight from the refrigerator
- Fill with water and drop from counter height five times
- Open and close the top and the opening mechanism 100 times
- Wash 10 times according to the manufacturer’s instructions
Performance: We evaluated how well the mugs retained heat and cold.
Leak Resistance: We rated the mugs on how well they resisted leaking.
Ease of Use: We evaluated how easy the mugs were to open, close, hold, and drink from.
Durability: We rated the mugs for damage during testing and for odor retention.