Only one—but it'll cost you $50. From the Washington Post (hat tip to NRO):

The U.S. government last year announced a $10 million award, dubbed the “L Prize,” for any manufacturer that could create a “green” but affordable light bulb.

 

Energy Secretary Steven Chu said the prize would spur industry to offer the costly bulbs, known as LEDs, at prices “affordable for American families.” There was also a “Buy America” component. Portions of the bulb would have to be made in the United States.

 

Now the winning bulb is on the market.

 

The price is $50.

Secretary Chu, who received the Nobel Prize in Physics in 1997, is obviously a smart guy—but he should stick to things like “the development of methods to cool and trap atoms with laser light,” for which he won the Nobel. Because when it comes to matters of practical economics, the guy is a clueless idiot.