There is little prospect that retail sales in the Washington area will grow much this year, but retail expansion will continue nearly unabated.

The result is likely to be increased competition for the consumer's dollar by merchants, and increased competition for merchants by the area's shopping centers.

Both trends say much about what the decade ahead will be like for Washington area retailers. Increasing competition will introduce an era in which vacant stores and going-out-of business signs could become as common in enclosed malls as they are in strip shopping centers and neighborhood retail complexes today.

New mall construction will slow, a victim -- along with urban sprawl and gas guzzlers -- of brutal increases in energy costs that are producing changes in the way all Americans live, work and shop. Downtown Washington stores will reap greater and greater benefits from the expanding Metro subway system. Neglected shopping areas in the belt between the urban core and the suburbs will be redeveloped and revitalized, as more and more merchants -- and consumers -- learn that enclosed arcades are not the only place to shop.

But for 1980, the momentum will still be with the malls, even though developers recognize the game is changing.

"In years past in areas of active growth, a shopping center developer couldn't lose," said John Franson, vice president of Ernest Hahn Co., which is planning an exurban mall in Woodbridge, Va. "If the population wasn't there when a mall started, it would be there when it opened."

Developers can't operate with that certainty any more because of energy pioneering anymore. They're becoming much more sophisticated."

If there is a last pioneer among Washington shopping centers, it is Fair Oaks, the 1.4 million square foot mega-mall now being built near the intersection of I-66 and Rte. 50 in Fairfax County by The Taubman Company of Troy, Mich. Hect's, Woodward & Lothrop, J.C. Penney and Sears, Roebuck and Co. will be the big stores and there will be a hundred or so little ones.

Taubman, a privately-owned company whose president and founder Al Taubman is one of America's master mall builders, has a reputation for building the bricks and biding its time for the business.

Lake Forest, the Taubman mall that opened more than a year ago in Gaithersburg, is still far from fully leased. Merchants in the center say sales are below their expectations and complain that the project was premature. s

Also still struggling to fill its vacant stores is Mazza Gallerie, which sits surrounded by affluence on the District of Columbia line at Wisconsin and Western avenues. Ten to 15 percent of its shops are still vacant, despite the success of the Neiman-Marcus anchor store.

The carriage trade will keep the Mazza plaza alive until the subway opens there in a couple of years, but further down Wisconsin Avenue the future of local retailing can be seen.

Just above Tenley Circle, in one of those places where subway construction and suburban centers left storefronts vacant, business is booming for Hudson's Bay Outfitters, a clothing, camping and sporting good store that opened a few months ago. No malls for them.

At the base of Wisconsin Avenue, the District of Columbia's biggest new retail project of the year is preparing to open its first section. Georgetown Park, a joint venture of Western Development and The Donohoe Companies, will have as its first big tenant Coran's a British-based home-goods store that migrated to New York a couple of years ago and will be right at home in Georgetown.

The old Georgetown Market a block away on M Street will also reopen this spring as a sort of boutique farmers market for the aubergine and alfalfa sprouts crowd.

The trend toward in-fill retail redevelopment is not restricted to affluent Northwest Washington.

At Maryland Avenue and 18th Street NE, where plywood and planks fill most store windows, the former headquarters of the Hechinger chain is being turned into a neighborhood shopping center anchored by a Hechinger home improvements store and a supermarket.

Federal and city funds are taking some of the risk out of that inner-city project, just as they encouraged reconstruction of the O Street market in the Shaw neighborhood and the opening of a new Giant supermarket next door. The District's next target for retail redevelopment is a few blocks away on Florida Avenue.

Downtown, the most important retail project of the year will be the start of construction on the Garfinckel block at 14th and H streets NW. Lots of little stores on the street level of new office buildings will add important increments to D.C. retail sales figures, but no large scale developments are scheduled to start this season.

Woodward & Lothrop is expected to announce plans later in the year for the block it owns north of its downtown flagship store.