"LEDs are based on semiconductor technology, just like computer processors, and are increasing in brightness, energy efficiency and longevity in a way that's reminiscent of the way each year's new crop of processors is faster and cheaper than last year's.
...
If you look at compact fluorescent lamps, they're four times as efficient as incandescent lights, and how many homes have those? It's less than 5 percent penetration."

But development is brisk, and the Department of Energy has estimated that LED lighting could cut national energy consumption for lighting by 29 percent by 2025. The total savings on U.S. household electric bills until then would be $125 billion.

LEDs have other advantages that are propelling them into niche uses, despite their upfront cost.

Current white LEDs will last up to 50,000 hours, about 50 times as long as a 60-watt bulb. That's almost six years if they're on constantly.
"
http://story.news.ask.com//article/20050414/D89FBSLG1.html
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