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There’s a lucid comfort in the warmth of a steaming-hot cup of coffee or tea, as well as a calming reassurance that whatever’s in your mug is going to keep you going for the next few hours. That is, if you actually get to enjoy it before it’s gone cold and stale.
If you’re prone to forgetting your cup right after you’ve poured it, or you’re routinely active or distracted throughout the day, you may be looking for a way to keep all of your hot beverages from turning into cold brew. Here’s our advice: Rather than reaching for the microwave or burning your tongue on too-hot coffee from a thermos, consider the humble mug warmer.
Functionally, a mug warmer is a tiny hot plate that sits on your desk and heats the bottom of your cup to keep the liquid inside hot. A good mug warmer will keep your drink warm without exacerbating unpleasant flavors via scorching. But it’s important to remember that, due to the inevitable effects of oxidation and the way these drinks break down chemically over time, there’s no way to completely preserve the body and flavor of freshly brewed coffee or tea.
“As brewed coffee sits, the perceived acidity in coffee gradually becomes higher because of the presence of quinic acid in the coffee. This effect is most commonly found when coffee is left on a heating plate for a long period of time,” said Chi Sum Ngai, founder of Coffee Project New York. “After a while, the acidity is going to shoot up. Coffee tends to be stronger in taste and not as smooth as when you first brew it.”
We tasted over 150 cups of coffee to find the best easy-to-use dripper for making pour-over coffee.
Tea experts we spoke with, including Bruce Richardson, owner of Elmwood Inn Fine Teas, unanimously agreed that tea loses its liveliness and turns stale the longer it sits.
All mug warmers aim to maintain a specific beverage temperature, according to what the company deems ideal for drinking; most of the warmers we researched and tested claimed to target a range between 120 °F and 155 °F (though in practice none could achieve a temperature above 145 °F). In our own testing, we found the ideal range to be between 130 °F and 140 °F. Any colder tasted lukewarm, and any hotter made sipping uncomfortable. Of course, your own preference may differ.
Since this is a category that’s rife with no-name brands and dubious marketing, we decided to test a few of the traditional mug warmers that had the best user reviews, a reasonable price point (below $50), and an attractive range of features. Our goal was simply to see whether a warmer would improve our overall drinking experience and if there was much variation among the myriad models available.
Of all the coffee makers under $100 that we’ve tested, the Ninja CE251 makes the best-tasting coffee, and it is easy to use.
To that end, we tested each warmer by brewing a pot of coffee in our favorite cheap coffee maker, using the same settings and the same beans (specifically, Kirkland Signature House Blend medium roast). We then measured the temperature and taste of the beverages over time. Our testing for tea was identical, using both black and green tea bags from Stash.
We also called in a couple of unique, higher-end products—the Ember Mug² and the Ohom Ui Mug—to see whether they could fill a niche that a simple mug warmer didn’t.
What it costs: about $32 (at the time of publication) Who it’s for: This warmer is ideal for people who want a simple, cost-effective solution to the problem of drinks going cold before their time. How it’s different: Unlike competing models, this affordable mug warmer maintains an ideal drinking temperature for hours and doesn’t scorch drinks. And while our other picks require you to use a proprietary mug, this one allows you to use all your old favorites.
Most basic mug warmers will keep your drink hot if you finish your cup in under 30 minutes, but very few will do the trick for those who sip at a slower pace. The Bestinnkits Smart Coffee Warmer is one of the only models we found that can sustain a comfortably warm temperature for hours, while also minimizing the harshness that some mug warmers impart on a drink’s flavor over time. The Bestinnkits warmer functions as a small hot plate that activates automatically when it senses the weight of a mug, and it conveniently shuts off whenever you pick up the mug.
Most of its competitors allowed our drinks to get lukewarm after 35 to 40 minutes. But the Bestinnkits consistently keeps beverages between 133 °F and 135 °F for hours (and perhaps indefinitely). That’s not piping-hot, but it’s still pleasantly warm and within the optimal range for drinking. Though the Bestinnkits claims to be able to heat up cold or room-temperature liquids, we found this to be only technically true: This warmer took over two hours to heat up our drinks and offered no benefit over any other method of reheating.
If you call up a memory of “old coffee”—coffee that’s been sitting in its carafe, on a warmer, for hours—words like burnt or metallic might spring to mind. Most mug warmers bring out these same strong, unpleasant notes. The Bestinnkits is no exception, but I found that it produced the least-offensive kept-warm coffee of the mug warmers we tested, and the coffee was noticeably less gross than brew left in a coffee-maker’s carafe.
I wasn’t able to distinguish between coffee kept hot on the Bestinnkits warmer and coffee that I let cool and then reheated in my microwave. But not having to get up and microwave my coffee was certainly more convenient. Obviously, my judgments regarding taste are subjective, but I feel confident saying that if you really want to preserve the very best flavor, you should consider paying more for the Ember or Ohom mug.
Although the Bestinnkits warmer was generally a joy to use, it does have a few notable shortcomings. Unlike some of the other mug warmers we tested, including models from Cosori and Vobaga, the Bestinnkits doesn’t have temperature-control settings—the warmer is simply on or off. However, the warmers we tested that did offer custom temperatures performed poorly. None of them could keep a drink warm for long, even on their highest settings. Still, it would definitely be a plus if this warmer had temperature control.
Despite the misleading “Smart” in its name, the Bestinnkits warmer does not include smartphone connectivity, and it’s also not as petite as some of the other models we tested. Still, it comes in a handful of colors, and it’s the only warmer we tested that accommodated and sustained heat in mugs over 10 ounces—in our tests, it successfully warmed mugs with up to 16 ounces of liquid. (You can even get a version that comes packaged with a 14-ounce ceramic mug.) Smaller mugs are actually more likely to be a problem, since your mug and liquid need to weigh at least 12.8 ounces in order to activate the automatic heating function.
Finally, Amazon and other e-commerce sites are full of generic mug warmers from brands with nonsense names, and Bestinnkits itself is certainly not a household name. This warmer comes with a two-year warranty, and the Amazon listing claims it is FCC- and UL-certified for safety (though the packaging does not mention this certification). But even though we liked the way it performed in testing, we can’t speak to the quality of support Bestinnkits might offer down the line. Bestinnkits Smart Coffee Warmer$30 from Amazon Cosori Coffee Mug Warmer $34 from Amazon Vobaga Coffee Mug Warmer$22 from Amazon Bestinnkits Smart Coffee Set $40 from Amazon
What it costs: $130 (10-ounce) or $150 (14-ounce) Who it’s for: This mug is good for people who move around a lot during the day, rather than sitting for extended periods at a desk. It’s also ideal for coffee or tea aficionados who want the best possible flavor preservation over a long period of time. How it’s different: This mug heats itself with a built-in battery and heat source, which means you can walk around with coffee that will reliably stay at your preferred drinking temperature.
When the Ember Mug was introduced a few years back via a crowdfunding campaign—at the height of the let’s-make-everything-“smart” craze—it took a lot of, er, heat in the press. A coffee mug with a battery that you have to control with your phone? Really?
But it turned out that owners truly liked the thing—as does noted coffee guru James Hoffmann (video). And since then it’s caught on to the extent that even Costco stocked it at one point. Naturally, we had to check it out.
Rather than having a contact heat source, as traditional mug warmers do, the Ember has a heat source that’s built into the mug itself (which is also equipped with sensors to regulate the temperature of the liquid inside). The Ember comes in clean, neutral shades that blend handsomely into any space. And in every category of our testing, it performed better than even the best mug warmers.
The Ember Mug pairs with your smartphone over Bluetooth, and its easy-to-use app allows you to monitor and control the temperature of your drink. You can select preset temperatures for common beverages like black tea, green tea, coffee, cappuccinos, or lattes. Or you can create custom profiles, setting the temperature of the mug anywhere between 120 °F and 145 °F.
This mug warmer works as advertised. Not only did the Ember successfully keep my drink within a few degrees of my ideal drinking temperature, but it managed to do so when I took it on a walk with my dog in brisk, 40 °F weather. It’s also the only thing we tested that could actually heat up liquid from room temperature, and it did so in about 20 minutes.
Whereas other traditional mug warmers allowed our coffee to develop an unpleasant acidity over the course of a couple hours, coffee kept in the Ember retained more of its initial flavor. Across all of the mugs and mug warmers we tested, every cup of coffee eventually went stale—this was an unavoidable effect of the oxidation that occurs when freshly brewed coffee or tea sits out. The Ember won’t fool you into thinking the coffee you forgot about for a few hours is a fresh cup. But it also won’t make it worse by burning it or adding acidity or bitterness, like most of the other mug warmers did.
“I think maintaining drinking temp, rather than serving temp, is the way to go,” said Hoffmann. “Thermoses work well but tend to hold the coffee hotter. I haven’t tried anything else comparable to the Ember.” In a blind taste test (video), Hoffmann even found that keeping coffee hot with the Ember yielded less harshness and bitterness than other traditional methods of reheating.
Although the Ember is indisputably the best at keeping drinks hot without ruining their flavor, there’s no getting around the fact that $150 is a lot to spend on a mug, smart features or no. (The Ember also comes in a smaller, 10-ounce model for $130, which is objectively still a lot of money for dishware.)
We think it could be money well spent for the right person (the one who’s already spending more than $20 per 12-ounce bag for their coffee, and who cares more about long-lasting, consistent flavor than about bargain hunting). But we should be clear: Even though this thing costs an ungodly amount of money for a drinking vessel, your $130-plus doesn’t buy you a flawless product.
For us, the biggest disappointment is that the mug’s battery lasts only between 80 and 90 minutes, and it takes over two hours to fully charge from empty. That means you need to be diligent about returning the mug to its home base whenever it’s not in use.
While it’s paired with your phone, the mug won’t charge if there’s any liquid inside. The Ember will maintain its current charge and assigned temperature, but if there’s still tea in it, that battery percentage won’t budge—no matter how long you leave it on the charging base. In addition, the mug isn’t dishwasher-safe (which is a small annoyance, but it’s one that some owners might come to resent over time).
Ultimately, if you’re someone who loves smart gadgets, and you’re proactive about keeping your devices charged at all times, the Ember is an excellent choice. If you like your beverages to be hotter or colder than 135 °F (which is the temperature maintained by our other recommendations), the Ember also offers you the most freedom to customize your preferences. Ember Mug²$130 from Amazon$145 from Walmart$150 from Best Buy Ember Temperature Control Smart Mug$130 from Huckberry$125 from Walmart$110 from Amazon
What it costs: $88 Who it’s for: This mug is for those who want to free up outlet space by combining their wireless phone charger with their mug warmer—and do it all with style. How it’s different: Did we mention it’s also a wireless smartphone charger?
At first we were skeptical of Ohom’s quirky Ui Mug, which comes with a pad that doubles as a mug warmer and a wireless phone charger. Yet it works surprisingly well.
It’s closer to a traditional mug warmer than it is to the Ember, but in some ways it’s like a hybrid of both. The base of the Ui Mug has metallic particles that react with the charging pad using magnetic induction, effectively working like an induction stovetop. Although the base doesn’t operate as a traditional hot plate (the way mug warmers like the Bestinnkits do), it does rely on contact between the mug and charging pad to keep liquids warm. That means you can’t use other mugs with it or carry it around and expect it to keep a constant temperature (as you can do with the Ember).
Even with those shortcomings, the Ui Mug stands out because it keeps drinks warm longer and more consistently than any of the other basic mug warmers we tested. On top of that, it’s a solid wireless phone charger.
It provides a steady charge even through thick phone cases. And though it’s not certified by the Wireless Power Consortium (which oversees Qi wireless charging standards), our testing indicates that Ohom’s advertised 7.5-watt iPhone charging rate is accurate. It was able to charge my fully drained iPhone 12 mini’s battery to about 30% in 30 minutes and 60% in an hour (which was comparable to the results we saw from our top Qi wireless charger picks at the time).
Of the mugs and warmers we tested, Ohom’s design is by far the most attractive. The Ui set comes with a matching mug, lid, and charging pad in a variety of beautiful colors. And the mug is made of a thick and high-quality ceramic—it even escaped a few accidental drops completely unscathed.
You can’t control the temperature in any way, but our testing showed that after about a half-hour of sitting undisturbed, the Ui Mug will keep a beverage at about 135 °F, which we consider ideal. When I left coffee alone in the Ui Mug for a couple of hours, it still tasted pretty good; acidity and bitterness were minimal compared with what I got from traditional mug warmers like the Bestinnkits (if not quite as well controlled as in the Ember).
The Ui set may seem like it’s simultaneously overkill and not quite essential for coffee or tea lovers who already have a wireless charger at their desk, but we think it’s actually a pretty smart use of space. If you follow scientific guidance and confine your caffeine consumption to the morning (or no later than the early afternoon), the Ui Mug won’t simply be taking up valuable desk real estate the rest of the time. (If you primarily drink herbal tea or decaf, disregard the scientific guidance above.)
Our general opinion: If you’re in the market for both a wireless charger and a mug warmer, this is a particularly sleek and pretty option. It takes up little space on your desk, and the colors are fun and appealing. The Ui is great if you’re looking to free up a slot on your power strip, and this mug, unlike the Ember, is dishwasher-safe. Ohom Ui Mug$98 from Amazon$74 from Nordstrom
Haley Perry is an associate staff writer at Wirecutter covering video games and technology. She used to review video games full-time, and she’s also a big fan of mezcal. If you get enough in her, she may just admit that she still plays The Sims ... a lot.
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