RICHMOND, JUNE 15 -- In a confrontation that Virginia Power says holds extraordinary implications for future electricity supplies across the state, the giant utility today defended its plan for a new generating station against charges that it would amount to a $126 million boondoggle.

Over five sometimes tense hours, including a spirited, witness-stand defense by company President Jack H. Ferguson, the utility asked state regulators to grant its request to build a futuristic power station in suburban Richmond to keep pace with the ever-rising commercial and residential demand for electricity.

According to utility specialists, the issues being debated today and Tuesday in the State Corporation Commission courtroom go far beyond Virginia Power's request to build Chesterfield 7, a station named for its planned site in Chesterfield County just south of here.

With Chesterfield 7, Virginia Power is attempting not only to preserve its virtual monopoly on electricity supplies in the state, but also to abandon its practice of relying on the larger and more expensive coal-fired and nuclear power plants that have been the mainstay of the industry for years.

Dogging Ferguson and other utility executives throughout the hearing before the commission was an array of lawyers for smaller energy companies, consumer groups and, most significantly, for the commission staff itself, which opposes the project's immediate construction.

"There is no reason why ratepayers should be asked to pay for this type of experiment," commission staff attorney Kenworth E. Lion Jr. declared during a heated exchange with Ferguson. Power plant construction costs ultimately show up in consumers' electric bills.

"You made some remarks . . . suggesting we're incompetent and ignorant," Ferguson fired back at one point.

"Let's get on, let's get on to the issues in this proceeding," interjected commission member Preston C. Shannon.

Ferguson and other company executives contended today that they can best judge the state's power demands for the 1990s and should have authority to construct and manage the new technology that uses a state-of-the-art turbine and waste heat from that device to produce electricity.

Denying the utility the right to construct Chesterfield 7 "would set a dangerous precedent {because} Virginia Power would lose control over the power production" it now has, said utility attorney Evans B. Brasfield.

Critics of the company's plan, including small energy producers such as Fairfax County that are eager to sell their own electricity to Virginia Power, said there now is plenty of power to go around -- enough to warrant a delay or even cancellation of Chesterfield 7.

"Building this facility will be more costly and less efficient than buying power" from small producers, Assistant Fairfax County Attorney Marcus D. Williams told the three-member commission.

"We don't believe Virginia Power has set forth the total justification for this massive cost," Williams added.

Fairfax County plans to build a $200 million trash-to-energy plant at the Lorton landfill to convert 3,000 tons of refuse a day into electricity.

The county is negotiating with Virginia Power in an effort to start selling it electricity from the Lorton plant by 1990, the year Chesterfield 7 might come on line, a spokeswoman for the county said today.

Newport News is developing a similar generating plant and Beverly L. Crump, an attorney for that Tidewater city, echoed Williams during today's hearing, saying, "Virginia Power should not be allowed to build Chesterfield 7 so long as small power producers are available."

Yet, even as Ferguson and other utility officers acknowledged an abundance of power from smaller producers, they stressed that the emerging industry was too unreliable and in some cases too poorly financed to serve as a stable source of electricity into the 21st century.

"We wouldn't blindly go ahead and build" the Chesterfield plant, Ferguson said from the witnesss stand.

"I don't think this commission would let you," Shannon added. The commission is expected to rule in the case by September.