The plan to shutter 12 plants brings TXU in line with a broader industry shift as power companies shed less efficient facilities in the midst of an electrical power glut. The plants' 55 workers will be offered jobs elsewhere in the company, TXU officials said.

TXU's cost-reducing move comes less than a week after it requested a 3.5 percent rate hike, its fourth request in two years totaling a 24 percent overall increase.

Plans to close the North Main site -- which has produced electricity in Fort Worth for about a century -- come five years after TXU first began marketing the site for sale and as other power companies shut less-used plants.

The units to be closed total 1,471 megawatts of generating capacity. TXU can generate 23,000 megawatts of electricity from its 22 other plants, located from Fort Stockton in West Texas to Martin Lake in East Texas.

"Texas has a sufficient supply of power, and idling these plants will have no impact on reliability of service for TXU customers," said Richard Wistrand, TXU Energy sector vice president.

In 2001 TXU sold its Handley generating plant in east Fort Worth, as well as its Mountain Creek plant in Dallas County, to Exelon Corp. of Philadelphia as part of a partial divestiture of generating plants required by Texas deregulation law. TXU now buys most of the output from those plants.

Other power companies have been shedding generating plants as well. American Electric Power announced this month that it will sell 10 plants in central Texas to Sempra Energy of California. Four other Texas plants owned by American likely will stay mothballed.

Reliant Energy of Houston mothballed 22 plants on the East Coast because it could find no regularly profitable markets for their electricity.

Wistrand said TXU officials decided to shutter the plants because of their high operating cost and the company's ability to buy power from newer plants.

Newer, more efficient plants have been built as the industry has expanded over the past four years.

In the last two years, several new generators have been opened around the Dallas-Fort Worth area, including two new Tractebel plants in Ellis County, a 750-megawatt facility opened last August by American Electric Service generator at Wolf Hollow near Granbury and a new plant east of Dallas opened last year by a subsidiary of Florida Light & Power.

Tractebel also is finishing a 720-megawatt generator northwest of Fort Worth, near Bridgeport.

The future of the shuttered TXU plants is an open question.

North Main has been little-used in recent years. TXU has been unsuccessful in trying to sell the plant since 1999 because of lingering environmental issues. The only public mention of a potential use for the 55-acre site has been a proposed downtown campus for Tarrant County College, but no serious negotiations have taken place.

The utility also said it will mothball the three-unit Eagle Mountain Electric Station in northwest Fort Worth. That plant, with 665 megawatts of capacity, opened in 1954 and has been expanded several times.

TXU spokesman Rand Lavon said that although North Main will be closed for good, the utility could bring Eagle Mountain back on line to meet peak demand.

The seven other plants slated for closure include the one-unit Parkdale Plant in Dallas, a one-unit plant in Red River County and three of five units at the Morgan Creek station in Mitchell County.

In addition to the Eagle Mountain plant, TXU will mothball a 153- megawatt unit in Collin County.

State officials say the Electric Reliability Council of Texas (ERCOT) grid has about 75,000 megawatts of generating capacity. In August, peak demand caused by heavy air-conditioner use exceeded 60,000 megawatts for the first time ever.

On Monday, the grid system used 30,512 megawatts at midafternoon, according to ERCOT.

Wistrand said that the Eagle Mountain and Collin County plants "are also under evaluation for full retirement in the future."

The North Main plant, just across the Trinity River from the Tarrant County Courthouse, has been a landmark for generations. It was part of the once-thriving North Main business district that extended north from the courthouse.

Fort Worth Power and Light Co., organized in 1911 through the merger of three smaller entities, built the North Main plant in 1912 as a successor to a previous generating facility on the site.

The ochre brick veneer was considered something of an architectural masterpiece at the time of its construction.

The original plant had 11 bays, generating power from coal. In 1922, operators added a gas-fired steam generator. When Fort Worth Power and Light Co. became part of Texas Electric Service Co., a forerunner of TXU, in 1952, the company added six new generating bays and a 320-foot concrete stack.

TESCO later built a one-story building across Main Street to the east to supplement the plant.

The North Main plant has no permanent employees. TXU has shifted workers there from other locations on the rare occasions when it has fired up the North Main generators.

Efforts to sell the North Main plant have been stymied by potential environmental problems. TXU has remedied some problems with toxic waste buried in the area, spokeswoman Carol Peters said.