Remember when restaurant wine by-the-glass selections were limited to “red, white and pink”? If you were born in the 1950s, you probably do. Then we became a wine-loving nation that craved variety, and restaurants responded by offering more wines by the glass. It was a great way to try something new without committing to an entire bottle. We could drink something interesting with our appetizers before enjoying a main-event bottle with the entrees, or improvise a flight of different wines to match dishes throughout the meal.

Star Wavra, co-owner of Field & Main in Marshall, Va., draws a glass of the house red blended at Early Mountain Vineyards. (Neal Wavra)

Of course, we kvetched about the cost. Twenty dollars or more for a glass of wine? Well, yes, if it’s a top-flight Burgundy or California cabernet. But still, that adds up. Once again, restaurants responded, by offering more wines on tap. I first wrote about tap wines six years ago when they began to appear in Washington-area restaurants. Today, the tap wine market keeps expanding, with more high-quality wines being marketed exclusively in this format for restaurant sales.

Here’s why you should care, and why you should seek out tap wines when you dine out. The primary reasons are cost and freshness. A standard bottle (750 milliliters, or 24.5 ounces) holds about five 5-ounce glasses, or four 6-ounce pours. Restaurants typically price a glass of wine at just under the wholesale cost of the bottle. That way, if they only sell one glass and have to pour the rest out, they pretty much break even. The rest is profit. But you don’t know whether the bottle they’re pouring from was opened two minutes or two days ago.

A 20-liter keg, on the other hand, cuts the cost of production by eliminating 26 bottles, the labels, foils and corks. Shipping is also cheaper, because kegs are lighter than the total weight of all those bottles. The kegs are either stainless steel, which are returned to the winery for reuse, or recyclable plastic with a collapsible aluminum bag inside to protect the wine. The packaging keeps the last glass of the keg as fresh as the first.

I became convinced recently when I tasted a pinot noir from Peregrine Ranch, a Sonoma County winery that sells wines exclusively in kegs for restaurants. The wine, grown on Sonoma Mountain, was delicious and velvety, with cherry and raspberry flavors accented by smoke. It was easily the equal of other California pinots costing $30 or more a bottle. Yet at $265 a keg, it costs a restaurant the equivalent of about $10 a bottle — or $15 or so at retail.

At Roofers Union in Adams Morgan, you can buy a glass of the Peregrine Ranch pinot for $12, a half-liter carafe for $24, a 750-milliliter “bottle” for $40 or a half-gallon “jug” for $85 (or half price for jugs on Wednesdays). General Manager Dave Delaplaine keeps eight wines on tap. One of his current favorites is a Tocai from Millbrook winery in New York’s Hudson Valley.

These are not wines for cellaring. “The idea is to find wines that are true to type, but since they are for by-the-glass, they should be easy drinking,” says Jocelyn Cambier, a French-born importer specializing in wines in kegs for restaurants and bag-in-box for retail. “In France we say they are easy to digest: You finish a glass and you want another, or else you get hungry and start ordering food.”

Cambier’s company, Tapwines.com, works through an Ashland, Va., distributor called Tap 26. It carries Peregrine Ranch.

“When keg wines started, people were taking bulk wine, putting it in kegs and slapping any label on it,” says Jeff Meyer, owner of Vintap-Peregrine Ranch, a company that farms nearly 400 acres of grapes in Sonoma County. Meyer decided to enter the keg market five years ago so he wouldn’t be competing directly against wineries that purchase his fruit. Plus, he saw an opening for a market niche.

“If I took bottles into Fog City Diner in San Francisco, I’d be up against an awful lot of competition,” Meyer said in a telephone interview. “But there were not a lot of people offering Sonoma Mountain pinot noir in kegs.”

The keg market offers an opportunity for local wineries to enter the restaurant market as well. Winemaker Michael Shaps sells several wines on tap through his Virginia Wineworks label. Maryland’s Old Westminster winery sells wine in kegs to Parts & Labor in Baltimore, Aida Bistro in Columbia, Market Tavern in Sykesville and Eno wine bar in Georgetown.

When Neal and Star Wavra opened Field & Main in Marshall, Va., last fall, they offered three wines on tap that Neal Wavra helped blend at Virginia’s Early Mountain Vineyards. So far, those house wines on tap account for 10 percent of their by-the-glass sales.

Better variety, better value and environmentally friendly. Three more reasons to enjoy wine by the glass — or carafe — on your next evening out.