When the power would go out just a few years ago, Herbie Smith, a district manager of the Southern Maryland Electric Cooperative, could knock on some farmhouse doors and explain that SMECO was working on it. Now, there are too many doors to knock on, and no one wants to listen.

"We've got a different customer base," Smith said. "It was tobacco farmers and livestock farmers and watermen. . . . Now, they are younger, and they have higher expectations. They are mathematicians and engineers."

Smith doesn't have time to tell them, anyway. In place of the scattered farmhouses that the region's rural electric co-ops were invented to serve 70 years ago, there are thousands of 4,000-square-foot homes -- all in need of power to run air conditioning, computers, dishwashers, garage doors, television sets and DVD players all day long.

Not many businesses would complain about increasing demand for their product, but the electric co-ops are racing to reinvent themselves and investing millions in power lines to serve Washington's expanding exurbs.

Installing equipment is expensive and complicated for the region's two co-ops -- SMECO and Northern Virginia Electric Cooperative, or NOVEC -- which are nonprofit. And by law they have an additional problem that puts them in conflict with modern times:

They have to persuade thousands of new customers to participate in the running of the co-op -- annual meetings must have a quorum, although proxy voting for the board is allowed -- or the co-ops lose their nonprofit status.

That's tough: The new customer/member is more often than not a commuter with a working spouse, children in school and, thus, no time to attend meetings.

In September, NOVEC resorted to door prizes to lure customers to the annual meeting. Members who attended or voted by proxy were eligible to receive lawn mowers, digital cameras, flat-screen TVs and $50 gift certificates for Target or Sears. Food was also served.

"In my opinion," said Jane Beyer, a longtime NOVEC customer, "one of the things that draws them is the food. This year it was a spaghetti dinner."

For its annual assembly in late August, SMECO hosted a picnic in Hughesville with musical entertainment by the group Country Memories and giveaways that included a used company pickup. About 1,440 customers out of more than 130,000 voted -- most by absentee, but it met the bylaws.

Many newcomers have no clue that the law requires customers' participation as members.

"I don't pay attention to anything but the bill and how much I'm paying," said Gainesville hairstylist Jessie Owens, 50, a NOVEC customer for a year.

Peter Stark, 54, of Gainesville has been buying power from NOVEC for more than three years and has never been to a meeting. But he does at least know what a co-op is.

"I voted by proxy," said the computer systems engineer. "It would have been nice to go, but I've never been able to get there. I've meant to go every year."

Rural electric cooperatives were born out of Franklin D. Roosevelt's New Deal, to bring electricity to far-flung farms that profitmaking utilities refused to serve. Today the Washington region's two co-ops, and 900 others across the nation, survive as nonprofit entities that are owned by ratepayers and qualify for low-interest federal loans and federal aid for repairs when disasters strike. The co-ops don't generate power but buy it from investor-owned utilities.

Co-ops typically pass any profit back to consumers by refunding money, a practice NOVEC calls "cashback." Last year, NOVEC returned $30.4 million to consumers. SMECO returned nearly $6 million. Rebates vary according to the amount of power customers use.

Because co-ops' distribution systems are aging and were built to support a few farms, not thousands of homes, they are upgrading their equipment, such as new wiring and transformer substations. They also try to provide the level of service their growing numbers of suburban customers expect.

NOVEC serves 123,528 customers in parts of Northern Virginia, from western Fairfax south to Stafford County and north to Clarke County. Over the next three years, the co-op will spend $90 million to keep up with a customer base that has expanded 28 percent since 2000 and continues to grow by about 6,000 customers annually. NOVEC is the 11th-largest of the nation's electric co-ops.

SMECO, the nation's seventh-largest co-op, with 130,060 customers, adds about 4,000 customers a year. The co-op "is going to have to spend big bucks," said Jack Williams, a longtime member of the board. "We will spend $50 million in the next two years just because of growth."

Some of that money will go to a pilot program in St. Mary's County to lay underground power lines for about 180 homes before they are even built, "in order to keep up with construction," said Smith, the district manager. "We're going to start using that methodology for more jobs."

As for reliability, NOVEC and SMECO appear to be almost on a par with the region's largest utilities, Dominion Virginia Power and Pepco, according to state records, although reporting requirements are different for the co-ops.

Still, as service is expanded, co-op customers can experience outages for no apparent reason -- on clear, calm days. A whole subdivision will be taken down so the co-op can extend power lines to another being built down the road. Sometimes a construction crew in the outer suburbs will knock over a utility pole and put dozens of homes in the dark.

In October, a truck ran off Gum Spring Road in Loudoun County, broke a pole and knocked out power to 13,000 homes, said Inia Burginger, a NOVEC spokeswoman. The circuits along Gum Spring Road were serving more customers than usual because a substation was being reconstructed.

Karin Kuropas, 35, a stay-at-home mother of four boys, said the South Riding power outage put her in a hairy situation.

"I was going to pick up my son," she said, but the garage door opener wouldn't work. "I couldn't get out of my garage, and I had to disconnect my garage and . . . get out and open the garage door" by hand.

But she called it a minor inconvenience. "I'm fine with NOVEC. I don't know much different. When I flip on the switch, the light comes on," she said.

And when it doesn't, she knows the power will come on eventually.

Critics suggest co-ops have outgrown their purpose and question whether they should be allowed to remain nonprofits that qualify for cheap federal loans and make refunds to their customers -- even as they run lines to million-dollar homes.

"The [program] has gone well beyond its original intent," said Laurence J. Malone, an economist specializing in cooperatives. "It raises considerable questions of having people of high incomes reap the benefits."

Williams, 84, the SMECO director, grew up on a tobacco farm outside Prince Frederick without electricity. He remembers why co-ops came to be in the first place.

Williams, a former president of the National Rural Electric Cooperative Association, still wears the old red sweat shirt emblazoned with a cartoon character, Willie the Wired Hand. Willie has a light socket for a head and a plug for his lower body and legs. He wears a big smile and white gloves.

"Wired hand" is a play on "hired hand," Williams said.

Electricity, he said, truly became the farmer's helper.

SMECO workers -- Mike Owens, left, Jeff Mayor, in white hat, and Nick Potts -- install power lines for a Southern Maryland subdivision.

The SMECO power lines are buried before the houses are built at a subdivision in St. Mary's County. SMECO adds about 4,000 customers a year.

Workers, from left, Matt Bowes, Wayne Fowler and Kip Pulliam set up a transformer. A utility official said it will spend $50 million in two years to meet growth needs.