When it comes to green alternatives, the light at the end of the tunnel might just be the LED, or light-emitting diode. Unlike incandescents, LEDs don't have filaments to burn out, and, more important, they don't waste the majority of their energy output on useless heat. Instead, they illuminate via the movement of electrons in a semiconductor material.

"LEDs have the hugest potential for the residential market," says lighting designer Nancy Clanton, founder of Colorado-based Clanton & Associates, a company specializing in sustainable lighting design. "Where CFLs fail, LEDs will surely take over. And color? Oh, my gosh—you can pretty much dial up any color you want with an LED."

So far, LEDs have been used commercially in dashboard indicator lights and traffic lights. But a few companies are starting to produce them for the home. Dallas-based Lighting Science, for example, offers LED bulbs that resemble incandescents in appearance and can be screwed into any standard socket. While light quality and color are crisp and white, the bulbs aren't nearly as bright as incandescents and, at least for now, are better suited for use in desk lamps or reading lights. Other companies, such as C. Crane and Ledtronics, are also offering LEDs, but the big guys—namely GE, Philips, and Sylvania—are about five years away from introducing their own versions.

"The battle we all face right now is cost," says Lighting Science president Ron Lusk. "The efficiency is great, but they are still cost-prohibitive." Indeed, his company's 30-watt "warm white" bulb costs almost $50. But Lusk is quick to point out that it costs 90 percent less to run than an incandescent and can last up to 50,000 hours, compared with a CFL's 10,000 hours and an incandescent's 1,200. "From a payback standpoint, it's almost free," says Lusk, adding, rather convincingly, "I truly believe that LEDs are the future of lighting."

Unlike CFLs, with their trademark squiggle, LEDs have yet to develop an iconic shape. Some look like traditional incandescents, while others, with their clear glass and exposed diodes, look like something out of 1950s sci-fi. The aluminum fins on some LEDs are heat sinks, which keep the bulbs cool to the touch.

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