Coffee can quickly turn tepid in a traditional mug. Could a smart mug that promises to keep it hot solve that problem?
How We Tested
Every morning I pour myself a cup of hot coffee. Then I go about my usual routine of feeding our dog and reading through emails, and when I return to take a sip of my coffee, it’s often tepid. At this point, I usually choose between reheating the coffee in my microwave (which will likely result in bitter, astringent coffee) or quickly drinking down the lukewarm brew before it gets any cooler. Neither is very appealing. Enter smart mugs. These devices, which often work with a smartphone app, can reportedly keep a hot beverage at a specific temperature for an extended period of time. My team and I were intrigued, so we purchased three models to test. Two models were made of ceramic-coated stainless steel and one was made of bone china. All were priced from about $79 to about $165. In addition to evaluating their ability to keep our coffee at the perfect temperature, we considered how easy the mugs were to set up and noted if they were comfortable to hold, pleasant to drink from, durable, and easy to clean.
How Smart Mugs Work
From the outside, these mugs look similar to a regular mug, but their thick bases house internal heating components, a high-capacity battery, microprocessors, and various temperature sensors. To charge their batteries, you place them on an electronic charging coaster. Once the mugs are fully charged, you remove them from their coasters, fill them with your hot beverage of choice, and use them freely until their battery power runs out. You can also use two of the three models while they are sitting on their charging coasters (more on that later).
According to several studies (as well as our own preferences), most people like to drink their coffee at temperatures between 130 and 160 degrees Fahrenheit. All the models in our lineup promised to keep coffee at temperatures within that range. The temperature settings on two of the models we tested were adjustable and could be set with a special smartphone app. The temperature of the third model was not adjustable. Instead, its internal heater promised to keep beverages at temperatures from 140 to 149 degrees.
Keeping Our Coffee Hot
We like having the ability to take our coffee with us as we move around our homes and offices, so we focused our first test on seeing how long the three fully charged mugs could keep coffee at 145 degrees while off their charging coasters. We checked the temperatures in 10-minute increments until their batteries died and the coffees cooled to 130 degrees. Next, we were interested in learning how adept the three mugs were at keeping coffee hot during typical use, so we repeated the first test, but this time we checked the coffee temperature after taking a sip from each mug. For the third test, we wanted to know if the fully charged batteries of the two mugs with adjustable temperature settings lasted longer when the mugs were set to a lower temperature (135 degrees).
Several jittery days later, we were disappointed by one model and impressed by the other two. In the first two tests, the battery of the disappointing model died relatively quickly, so this mug was able to keep coffee above 130 degrees for only 30 minutes—just 15 minutes longer than coffee sitting in a regular mug. One of the better mugs (an adjustable model) was able to keep coffee at a set temperature for an average of 50 minutes and within our ideal temperature range for an average of 70 minutes. The other preferred model (also an adjustable mug) kept coffee at a set temperature for an average of 70 minutes and within our ideal range for an average of 90 minutes. This model was also the most accurate in our lineup; it stayed within 2 degrees of the set temperatures. We also found that the two adjustable mugs kept coffee hot for 10 minutes longer when set to a lower temperature.
Testing Their Power Sources
As previously mentioned, two of the three smart mugs can be used while they’re sitting on their charging coasters (you can plug them into a standard electrical outlet). To test this capability, we set the temperatures of both mugs to 145 degrees, filled them with 170-degree coffee, placed them on their charging coasters, and recorded the temperatures of the coffees every 30 minutes for 5 hours.
Impressively, both mugs kept the coffee at a steady, consistent 145 degrees for 5 hours. However, at the end of the test, some of the coffee in each mug had evaporated, and both coffee samples tasted unpleasantly acidic and bitter. When we repeated this test, setting the two mugs to 135 degrees, there was less evaporation, but the coffees were still unpleasant to drink. The takeaway? For those who like to drink hot coffee at their desks, these mugs are good options, as you can drink from and refill the mugs throughout the day. However, we don’t recommend letting a single cup of coffee sit in one of these mugs for longer than about 90 minutes because evaporation will cause the compounds in the coffee to become bitter.
Next, we tested battery longevity. After fully charging all three mugs and removing them from their coasters, we used them for multiple short periods of 30 minutes each, with a 2-hour break in between each use. One mug’s battery power lasted for two 30-minute cycles, while the batteries of the better mugs lasted for three. Another note: We found it helpful that the apps of the two adjustable models displayed how much life was left in their batteries. We found it even more helpful that one of the apps sent an alert when it was time to recharge its mug. However, we did notice one important difference between our two favorite models: It took just 2 hours to recharge one, while it took nearly 6 hours to fully charge the other.
How Easy Are They to Use?
Finally, we considered how easy (or difficult) the models were to use. Each smart mug had its own set of graphic icons, flashing colored lights, and notifications. The display of one especially complicated mug featured between one and eight flashing red dashes to indicate different messages (for example, if the mug was charging or that the battery had died). We had to constantly refer to this mug’s manual to decode what each number of dashes meant.
We much preferred using the smartphone apps that we’d paired with the two adjustable models. Both apps were easy to navigate and provided us with helpful information. In addition to tracking battery life, we could also track coffee temperature. We appreciated that one app alerted us when its coffee had reached our set temperature and was ready to drink. We also liked that all three of the mugs had built-in safety features. One automatically stopped heating after being inactive for 2 hours, even if it was filled with coffee. And all the mugs shut off automatically when their sensors detected that the mugs were empty.
We love how easy some of these were to use, but even the most user-friendly smart mugs require slightly more care and attention than a traditional mug. For example, two manufacturers specifically mention that their mugs cannot be put in the refrigerator or freezer and urge users to be cautious when stirring with metal spoons, as they could damage the mugs’ coatings. Also, none of the mugs can be used in the microwave. Though one model is dishwasher-safe up to 140 degrees, all three mugs should be hand-washed for the best results.
The Best Smart Mug: Ember Mug², 14 oz
The Ember Mug², 14 oz is our favorite smart mug. It’s easy to use, and its temperature settings are accurate. Simply download the app, pair your device, set your desired temperature, and enjoy your coffee. If you don’t want to bother with the smartphone app, this mug is automatically preset to maintain a temperature of 135 degrees. However, we discovered that on this automatic setting the coffee temperature hovered closer to 130 degrees (both while the mug was positioned on its coaster and while it was off). This wasn’t a deal breaker for us. We loved that its battery charge lasted long enough for us to enjoy coffee at a set temperature for 70 minutes and within our ideal range for an average of 90 minutes. When placed on its charging coaster, the mug is capable of keeping coffee hot for 5 hours, but we don't recommend heating a single cup for longer than 90 minutes because its flavor will deteriorate. This mug was the most precise model we tested, and it took us just 2 hours to fully charge it, one of the fastest times in our lineup. And its smooth ceramic-coated stainless-steel walls and comfortable handle make the mug a pleasure to drink from. This mug extends the time we have to savor coffee or tea at our desired precise temperature. At roughly $130, this high-tech mug isn’t cheap, but the convenience it provides is unmatched.
- Test three smart mugs, priced from about $79 to about $165, including two ceramic-coated stainless-steel models with adjustable temperature settings and one bone china model with a fixed temperature range
- Track how long the mugs can maintain a set coffee temperature when fully charged and removed from their charging coasters
- Track how long the mugs can maintain a set coffee temperature while sitting on their charging coasters
- Track how many times a mug can be used for consecutive 30-minute sessions before needing to be charged
- Winner only: Evaluate the performance of the mug when used without its app, both when sitting on its charging coaster and when fully charged and removed from the coaster
- Leave coffee and milk in mugs overnight and then clean according to manufacturers’ instructions
- Wash each mug by hand 10 times
- Test durability by dropping each mug from a 6-inch height onto the counter
Performance: We evaluated the mugs’ abilities to keep coffee at precise temperatures and noted how long it took them to fall below our threshold temperature of 130 degrees.
Ease of Use: We noted how long it took to charge the mugs, the accuracy of their set temperatures, and how easy it was to decipher any alerts or notifications we received.
Cleanup and Durability: We assessed how easy the mugs were to clean and any damage sustained when they were dropped from a height of 6 inches onto a counter.