Customers grab a steamy lunch from the hot bar at a Whole Foods Market in the District. The store offers more than 20 hot selections daily. (Linda Davidson/THE WASHINGTON POST)

A grocery store used to be a place where people, you know, bought groceries to take home for making dinner. These days, grocery stores are our de facto home kitchens, too, turning out hot meals that, when combined with all other prepared supermarket foods, account for billions of dollars in sales. Yes, that’s billions with a “b,” as in “big boatload of bucks.”

Not about to miss out on the gravy train, supermarket chains continue to jump into the prepared foods market — or expand the line they’ve already launched. Rotisserie chicken has been commonplace for years, but now you can find a vast world of ready-to-eat foods at your grocery store: slow-smoked barbecue, artichoke flan, Chinese stir-fries, pork scaloppine, Vietnamese pho, spaghetti and meatballs, grilled tofu with cranberry-chili glaze, entire spreads based on Indian cuisine, even menus catering to seasonal holidays, whether Thanksgiving or Mardi Gras.

“People eat with their eyes,” says Chuck Berardi, regional executive chef for the Pennsylvania division of Wegmans. “I think they really have a difficult time walking by a bar that has hot food displayed when it’s so appetizing and the aromas are in the air. To me, you can’t walk by it.”

What Berardi’s saying, in other words, is that the hot bar may be the latest impulse purchase at the supermarket, the contemporary equivalent of snagging a Snickers bar or a copy of People magazine in the checkout lane. Which might explain why grocery chains are hot for hot bars.

Wegmans and Whole Foods Market are among the leaders in prepared foods: They hire chefs and prep teams for their stores and occasionally contract with third-party vendors to fill their massive collective of steam tables; together, the in-house and outside crews prepare dozens of dishes daily, breakfast through dinner. By comparison, chains such as Safeway, Giant and Harris Teeter tend to have more modest offerings, typically favoring comfort foods and relying heavily on the deep-fryer.

But is buying a meal at the supermarket merely an impulse purchase, something that’s not planned ahead of time? Feeding oneself dinner, after all, doesn’t seem to merit the same “impulse” tag as, say, grabbing a National Enquirer dedicated to actresses who look bad in bikinis. Something more must be driving the sales of hot meals, which, together with all prepared foods, were expected to generate about $19.5 billion for supermarkets in 2012, up by nearly $5.5 billion from the previous year’s projections, according to the Rockville-based research company Packaged Facts.

The term “lifestyle” pops up regularly in discussions about the trend toward hot foods in supermarkets — as in, the modern lifestyle doesn’t always afford people time to cook dinner. That’s not exactly a new idea. Joe Spinelli, a former supermarket consultant and now president of the College Park-based Restaurant Consultants, remembers how Boston Market tapped into the budding carryout segment in the late 1980s, when the company was known as Boston Chicken. Spinelli labels these types of hot, freshly made foods “home-replacement products.”

Supermarkets have found ways to cater to and expand on the market of eaters. Hot bars are “not just for the lunch trade anymore,” Spinelli says. “Those gourmet products are more for the dinner crowd than the lunch crowd. . . . They’ve elevated the product. It’s not just meat and potatoes. It’s gourmet foods.”

Executives at Whole Foods certainly want to reinforce that gourmet notion. Yes, they have heard the long-standing rumors that Whole Foods conducts some sort of nefarious bait-and-switch campaign at its stores: enticing you with good-quality ingredients in the grocery aisles but serving you hot meals made with inferior ones. It’s just not true, they say.

“This is kind of a myth that’s out there: that the prepared foods team is buying from the Syscos of the world and the big food vendors,” says Scott Crawford, Whole Foods’ prepared foods coordinator for the Mid-Atlantic region. “I share the same vendors with my produce counterparts. I share the same vendors with my seafood counterparts. The standard is one across the store. There isn’t a cheaper piece of chicken coming out of prepared foods, as far as the quality standards, as what you’re going to buy at the counter.

“There’s one quality for the whole store,” Crawford adds. “So the Bell & Evans chicken that we sell in the meat department, it’s the same chicken I use on my hot bar.”

One consumer demand driving the future of hot foods is the desire for more-healthful options. Wegmans and Whole Foods have tackled the issue head on. In 2009, Whole Foods introduced the Health Starts Here program, which, among other things, offers mostly plant-based hot foods with minimal salt and little fat. In 2010, Wegmans went so far as to send a team of chefs to Haus Hiltl in Zurich, Switzerland, considered Europe’s oldest vegetarian restaurant, to learn how to cook veggies better.

“They just really, as we do at Wegmans, take vegetable preparation very seriously,” says Jim Schaeffer, the company’s operations director of food preparation. “There was a time in America 20 years ago, if someone preferred vegetables, it would be simple steamed vegetables or maybe sauteed vegetables. People would spend more time on the center of the plate, the protein, than on the vegetable preparation. There are so many things you can do to make vegetables craveable — through spices, through different preparation methods.”

At almost any Wegmans, a customer strolling through the hot bar area can find 30 to 40 vegetable-based dishes, Schaeffer says. “That’s an area that’s just exploding for us.”

The future of hot foods at your local grocer would appear boundless. Whole Foods, for one, has already greatly expanded the offerings at both its P Street and Silver Spring stores in recent years; around two years ago, the number of hot-bar items at the P Street store increased by about 70 percent, notes Crawford.

If a Whole Foods store doesn’t have a hot bar, it’s “purely because of space,” says Paul White, the chain’s senior global coordinator for prepared foods. “It surely wouldn’t be because we don’t want them there. And it wouldn’t be because our customers don’t want them. It’s something we definitely know that our customers want.”

It would seem that supermarkets are inching closer to the Wal-mart Supercenter model, looking to cater to all your dining needs in one stop. You can grab a loaf of fresh bread, a bottle of wine and a to-go container of your favorite hot-bar items, probably for less than you’d spend at a local restaurant.

“It’s like going to a Costco. You can get about everything you want,” says consultant Spinelli. “You can probably get your car fixed one day.”