Engineers have been experimenting with using power lines for communications since the 1950s. But broadband over power lines, or what the Europeans prefer to call power line communications, has long been one of those just-around-the-corner technologies that holds a great deal of promise in principle but has never quite taken off.

Still, having witnessed earlier boom-and-bust cycles and continued lobbying by ham radio operators to have the plug pulled on the whole idea, makers of equipment that turns electrical outlets into Internet data ports believe that power line communications is now poised to mount a serious challenge to digital subscriber line, or DSL, and cable Internet services.

Why? Enabling technologies on both the transmission and consumer ends have made the service easier to deliver at an attractive price. The technology will have what is essentially a monopoly in most rural areas and many other places that DSL and cable Internet services do not reach. And consumers naturally would like to have broadband connections that give them more options for where they work or play. "There is definitely interest in the ability to plug your notebook into an electrical socket anywhere in your home or while traveling," says Michael Koch, vice president of strategy and regulation at Power Plus Communications AG, a division of the German electric utility MVV Energie AG in Mannheim [see photo, "Plugged"].

With DSL or a cable modem, depending on where your lines or jacks happen to be, sending e-mail wirelessly from the back porch on a sunny day may be nothing more than a daydream. Even with a Wi-Fi base station in place, running the IEEE 802.11 standard, some spots in the house are bound to get better reception than others. But if your utility company has installed power line communications equipment on the poles in your neighborhood, you have a lot more flexibility: attach a Wi-Fi port—say, Apple Computer's new AirPort Express—to a power line modem, and you can plug the wireless data port in anywhere there's an outlet.

With such possibilities in mind, a number of U.S. utilities announced trials of new power line communications services this year. Electric power companies such as Cinergy, Consolidated Edison, and Progress Energy have reported encouraging results, with thousands of households from California to Ohio signing on. A demonstration house set up by Current Technologies LLC near its headquarters in Potomac, Md., has attracted wide interest from utilities, investors, and the press.