Ember Mug² review: We put the smart temperature control mug to the test

That there is no specific word in the English language for the disappointment suffered on discovering your tea has gone cold before you got to drink it may seem odd to most Britons. The feeling is, can we suggest, brewtal.

A quick nuke in the microwave does, of course, bring up the temperature, but the tea or coffee never comes out tasting quite the same, and it certainly loses any freshness.

So, what is the best temperature at which to drink a hot brew? Tea should be sipped at 60-65C, according to the Royal Society of Chemistry, and coffee is best enjoyed a little cooler at between 40C and 60C.

However, the answer to that question raises another: how can one know when their cuppa has reached that optimum point? A tentative sip will usually reveal whether the brew is cool enough to swallow, but perhaps something a little smarter is needed if precise temperature intel and regulation are critical to maximum drinking satisfaction.

Enter Ember, the brand behind what it says is the world’s first temperature-controlled mug, which came about because of a plate of cold scrambled eggs.

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Yes, Clay Alexander, the founder and chief executive of the tech firm, says the idea for a self-heating cup came to him when his food got cold before he could eat it all.

Ember mugs are Bluetooth-enabled, controlled by a smartphone app and claim to keep drinks hot for up to 90 minutes. The brand counts Demi Lovato (who is also an investor in Ember), Reese Witherspoon and even chancellor Rishi Sunak among its fans.

But is the smart mug worth the almost £100 price tag? We put the 295ml black Ember Mug² to the test to find out.

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The mug itself is made from stainless steel with a scratch-resistant, food-grade, ceramic-reinforced coating, but what is inside – not the coffee – is particularly interesting. Built into the design are four sensors for temperature control and a dual-band microprocessor-controlled heating system. The heater and circulating convection current maintain the drink’s temperature between 50C and 62.5C, while the sensors detect the temperature of the contents and automatically switch on the mug when hot liquid is poured in. Equally, it enters sleep mode when it becomes empty.

A smartphone is not absolutely necessary with an Ember, every mug is preset to 57C, but using one means maximum control and makes the most of the features.

The app, compatible with both iOS (including Apple Watch) and Android devices, allows you to customise the LED colour on the mug and select a specific preferred temperature using a scrolling dial. We found pairing with an iPhone X was easy. Just hold down the power button on the bottom of the mug and it shows up in the app.

The app is super simple to use, with no complex features, and it sends notifications when the chosen temperature has been reached or when the mug’s battery is running low. There are a series of presets for different types of drinks to choose from and the capability to add your own. On top of that, there is a tea timer to ensure optimal steeping and recipes, such as beet latte and chai spiced white hot chocolate, to try out.

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The mug is powered by a lithium-ion battery that keeps drinks at the ideal temperature for 90 minutes. Depending on how forgetful you are, that might not seem long enough – it certainly was not for us at times.

But that is where the charging coaster comes in. This circular saucer features the same coating as the mug itself and it looks exactly like a regular coaster, but this one sends power into the gold rings on the bottom of the cup to give it charge. Leave the mug placed on the saucer and it will keep drinks hot all day.

Our only complaint about the charging coaster is that it has to be plugged into the mains, so an extra socket is needed either at your bedside or workstation, wherever you do most of your tea and coffee drinking. A USB plug function would be perfect here.

We tested the black 295ml mug and loved the look of it. The design is minimalist and sleek, and there are no buttons or screens that need fiddling with that could diminish any air of sophistication.

We like that the LED light is the only giveaway that there is any electricity running through the mug and that it can be personalised. We went for an amber glow because it looks great against the matte black, but black works brilliantly with any hue.

Aside from the black mug we tested, the Mug² also comes in white and there is a metallic collection, including gold, stainless steel and copper models. There is also the option of a bigger 414ml cup, but the battery life is a quarter of an hour shorter than that of the 295ml version.

One thing we were concerned about was using a metal spoon in the mug in case it scratched the coating. Those fears turned out to be unwarranted and, despite consistent use, the coating remains perfectly intact, looking as good as it did when it came out of the box.

The Mug² is certainly weightier than a conventional ceramic mug, not overly so, but you can tell the difference. It feels sturdy and robust, though. The handle is comfortable to hold and the outside of the mug is cool to the touch – certainly no hotter than a ceramic cup – considering it has a heating element on the inside.

The drinking experience is also pleasant, thanks to the smooth matte finish. Interestingly, and despite the tech inside the structure, the mug is thin, in a good way. With closed eyes, one can almost imagine they are sipping from fine bone china – both tea and coffee taste as delicious as they should.

It is a well-known fact that heat affects flavour. No one enjoys drinking lukewarm tea or coffee that is meant to be hot, with the essence and aromas diminished significantly. With the Mug², that is never a problem. Drinks stay at the perfect temperature to the very last drop with no cold dregs.

We found that we most enjoyed both tea and coffee at 60C, which is a little hotter than Ember recommends (it suggests 58.5C for black tea and 57C for coffee).

One point to note is that the Mug² is not designed to warm up cold drinks. Ember says it is possible to heat from a cold temperature or room temperature, but it does not recommend using the mug as a heater because it will drain the battery and take a long time to bring up the temperature of cool drinks. The mug is simply designed to detect when the liquid inside has reached the chosen temperature and keep it there, which it does perfectly well.

This mug is not for putting in the dishwasher, but it is perfectly safe for washing by hand. We always dry our Ember with a tea towel immediately after washing to prevent any problems, and it must be completely dry before placing it back on the charging coaster.

Buying a mug that costs just shy of £100 is undeniably extravagant by most people’s standards. We cannot deny that drinking from it feels lavish – that is what comes from a lifetime of accepting that sometimes your tea or coffee will go cold before you get to it. But having to no longer suffer that disappointment is a joy, and we have become spoiled to the point where lukewarm coffee is now unthinkable. Life is always going to present snags that cause annoyance and disappointment that you have little control over. Tepid tea and coffee are, however, no longer among them with the Ember Mug².

We also trialled the Ember travel mug², putting it head-to-head with the best reusable coffee cups available now