Once found only in boutique coffeehouses, cold-brew coffee has grown up, with sales rising 115 percent between 2014 and 2015. Starbucks and Peet’s now sell it by the cup in their shops, and you can buy ready-to-drink bottled versions from companies such as Stumptown and Slingshot at Whole Foods, specialty grocers, and even some Target stores. Not surprisingly, several appliance makers eager to cash in on the trend sell low-tech systems that take the mess out of mixing up a batch of cold-brew coffee at home.

(Read our cold-brew coffee maker review, which covers the Bruer Cold Bruer, Oxo Cold Brew, BodyBrew The Bod, Toddy Cold Brew System, and Fellow Duo Coffee Steeper.)

Cold-Brew Coffee 101

Before we get to what cold brewed coffee is, let’s be clear about what it's not. Cold-brew coffee is a very different beast from either iced coffee or the bottled coffee products (cappuccino, mochaccino, and other coffee-based drinks) sold at the supermarket. All of those start with standard hot coffee that’s then chilled, creating a drink that has all of the bitterness and acidity of regular coffee, just minus the heat.

To mask that bitterness, many coffee drinkers (and manufacturers of the bottled beverages) add heaps of sugar and glugs of milk or cream—and plenty of calories with them. “Some of the bottled coffee products we’ve tested have as much sugar as a can of soda,” says Maxine Siegel, a registered dietitian and manager of food testing at Consumer Reports.

Cold-brew coffee, on the other hand, begins with the same beans you’d use for regular coffee, but they’re ground more coarsely, then mixed with cold or room-temperature water and left to sit for a very long time: Coaxing flavor out of the grounds with cool water can take 12 to 24 hours or even longer. To avoid a weak, watery drink, cold brewed coffee also requires at least twice the grounds needed for traditional hot brewing, which explains why cold-brew coffee can be pricey, whether you buy it at a coffeehouse or supermarket, or whip up a batch at home. 

Make no mistake: Do-it-yourself cold-brew coffee makers aren’t a necessity; they’re essentially steeping chambers for the water and grounds. But they make preparing and filtering the coffee neater and less cumbersome. (Trying to make cold-brew coffee using, say, a carafe and cheesecloth can be a messy and tedious affair.) The machines also make it easier to experiment with the ratio of water to coffee until you find the one that produces the cup best-suited to your tastes.

What comes out of most cold-brew coffee makers after all of that steeping isn’t ready to enjoy. It’s a thick concentrate that you dilute with cold or hot water or milk, depending on the desired temperature and strength, before drinking.

Three types of cold-brew coffee.

The Bitter Truth

Why bother with all of the added time and expense of cold brew? Because of how it goes down. Fans say that cold brewing makes for a far smoother drink, without much of the bitterness and acidity of traditional coffee. In fact, a cold-brew coffee and a hot-brew coffee made with identical grounds will have a completely different flavor profile because compounds in the beans react very differently to cold water than they do to hot.  

Cold brew might also be a healthier choice than traditional iced or chilled coffee drinks. Because of its distinctly mild flavor, drinkers are less likely to load up cold brew with milk and sugar—and all of the added calories they bring.

Another selling point of cold-brew coffee is its extended shelf life: It will keep in the refrigerator for up to two weeks. Regularly brewed coffee doesn’t store well in the fridge and starts to go stale shortly after it’s made because of an aromatic compound that degrades as it cools­­—all something to keep in mind this summer when you’re looking for a pick-me-up that will also cool you down.


The Science of Smooth

Standard Hot Coffee

vs.

Cold-Brew Coffee

As any caffeine addict knows, a regular cup of joe starts with hot water (between 195 and 205 degrees Fahrenheit) and coffee grounds. The water dissolves oils, acids, and other compounds out of the grounds, giving coffee its familiar acidity and eye-opening aroma. The hot water also degrades acids, creating coffee's bitter notes.

The absence of hot water means that the oils, acids, and other compounds dissolve much more slowly. The acids also aren't degraded, making for a much smoother beverage, free of bitterness. One downside: This coffee's aroma is barely noticeable because heat is what releases it from the grounds.

Editor's Note: This article also appeared in the June 2016 issue of Consumer Reports magazine.