Light-emitting diodes, or LEDs, are four times more efficient than incandescent lights and greener than compact fluorescent bulbs (think: mercury). They also last up to 15 years before burning out.
So why aren't they everywhere?
Because they're expensive—created on a pricey layer of sapphire.
Until now. Purdue University researchers report a novel technique using cheap metal-coated silicon wafers to make LEDs.
Cheaper is better. Widespread LED use could cut electricity consumption by 10 percent.