When Starbucks debuted cold-brew coffee in its stores in 2015, iced drink sales reportedly surged 20 percent. The chain didn’t invent the concept, of course. Cold-brewed coffee has long been a New Orleans delicacy, and Blue Bottle and Stumptown started embracing the technique in the early aughts.

Starbucks did bring cold brew to the mainstream, though. These days most coffee companies, from Dunkin’ Donuts to Devoción, a cult NYC cafe, offer it year-round. Cold-brew concentrate is fairly shelf-stable, too, and so packaged iterations abound.

“The United States is becoming a cold-brew nation,” Oliver Strand wrote in The New York Times in June 2017.

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Despite widespread availability and appeal, however, questions plague the category. What’s the difference between iced coffee and cold brew? And why does the latter cost so much?

We hear you. Coffee is complicated! Here are five of your burning questions about cold brew, answered.

Is it different from iced coffee?

Yes! Iced coffee is brewed hot and served cold. You chill hot coffee either by pouring it over ice, or refrigerating it for a few hours before serving. There are drawbacks to both methods, unfortunately. The former dilutes your brew quite a bit, and hours-old coffee is never going to taste super fresh.

Cold-brew coffee, however, is made by steeping coarsely ground coffee beans in room-temperature water for six to 12 hours. This creates a coffee concentrate you mix with cold water or milk.

Cold-brew devotees say it tastes smoother than typical iced coffee, and those who are sensitive to acid believe it is easier-drinking than hot coffee. (According to some estimates, “cold-brewed coffee is 67 percent less acidic than hot-brewed.”)

Why is it so expensive?

Unlike hot coffee, which goes from whole bean to hot mug in a matter of minutes, cold brew is a moving target that requires advance planning. Retailers have to start steeping coarsely ground beans in room-temperature water at least six hours before they want to serve it. Once supplies run out, they’re done for the day — there’s no running to the back to make a fresh pot.

This is tricky business, especially in a model as mercurial as hospitality. Think about the crowds that swarm an otherwise spacious rooftop bar or beer garden on a beautiful summer day. The same principle affects coffee shops. If the weather is unseasonably warm, or very large parties arrive unexpectedly, a small coffee shop can quickly deplete its pre-made cold-brew concentrate, leaving everyone empty-handed. As a result, retailers often hedge their bets by pricing their cold brew higher than hot coffee, which they have in (relatively) unlimited supply.

Does it have more caffeine than regular coffee?

It depends. Probably not.

“You extract more caffeine when you brew coffee with hot water,” Anna Brones writes in TheKitchn. “But, cold brew coffee is typically made with a higher ratio of coffee to water — we’re talking two to two-and-a-half times more — which means it is stronger than if made with a more conventional coffee-to-water ratio.”

Complicating things further, cold-brew concentrate is typically cut with equal parts water or milk, “which brings that caffeine level right back down,” Brones adds. Cold brew is typically less caffeinated than the same quantity of hot coffee, but a lot of factors affect the caffeine levels in coffee, including the provenance or blend of the beans, and how they’re roasted, ground, and brewed.

Can I make cold brew at home?

Yes! It’s simpler than you think! Here is VinePair’s recipe for never-fail homemade cold brew. Just remember to start steeping your grounds the night before you want to drink it. Then, all that’s left to do is strain, pour, and mix with equal parts water or milk. Easy like Sunday morning, even if it’s a Tuesday and you’re late for work.

How long does cold-brew concentrate last in the refrigerator?

If you make your own cold-brew concentrate, which we wholeheartedly recommend, it will remain fresh for 24 to 48 hours. Expiry on store-bought, packaged cold-brew concentrates varies, so be sure to read the labels.