The Federal Communications Commission yesterday approved nationwide deployment of new technology that carries high-speed Internet connections over electric power lines.

"Broadband-over-powerline" allows subscribers to connect to the Internet by plugging a modem into a conventional electrical outlet. Supporters said it could become a major alternative to cable modem and phone connections if FCC approval helps it attracts investment and the participation of major utility companies.

"The impact is significant," said William Berkman, chairman of Current Communications Group, a five-year-old Germantown company. Current already has pilot projects offering the service to 5,000 customers in Cincinnati and several dozen in Potomac.

Berkman said the company plans to introduce the service in parts of the Washington area within a year for $30 to $50 a month.

The FCC had limited the new technology to pilot projects while it studied the concerns of critics, including amateur radio operators who said it could interfere with their signals.

The FCC unanimously approved wider use of the technology after finding that the interference was manageable. It also set rules for monitoring interference.

"The presence of a third universal broadband connection will mean a robust choice for consumers and strong, healthy competition," FCC Chairman Michael K. Powell said in a written statement. On Tuesday, Powell took a tour of Manassas, where the technology is used.

Commissioner Michael J. Copps expressed concern that wider deployment could still run into problems, and he raised the question of whether the customers of power companies would be subsidizing a new business. But he voted to approve the deal, saying he hoped it would drive down the price of broadband.

Although the new technology would be installed on the lines of major utilities, which would share in the revenue, it is being developed and marketed by a number of upstart companies such as Current.

The company is privately held by investors led by Berkman and his family, who have been major investors in the cable and telecom industries. Other investors include Liberty Media Corp., a major cable programming company and a group of power companies. Current has raised $70 million. It partners with Potomac Electric Power Co. and Cinergy Corp., which give it access to their power grids. Current installs devices on the network that allow electricity and Internet signals to travel at different frequencies over the same wire.

Other companies offering similar technology include Communications Ltd. of Israel, Amperion Inc. of Andover, Mass., and Ameren Corp. of St. Louis.