How many Nobel laureates does it take to screw in a light bulb? We don't know because they're off painting rooftops with whitewash.

U.S. Energy Secretary Steven Chu, a Nobel prize winner in physics, created a bit of a stir recently when he suggested that if we would all just paint our rooftops white -- and all the roadways and sidewalks, too -- we could eliminate the same amount of greenhouse gases as removing all the world's cars from the roads for 11 years.

Not a bad idea
A more practical idea might be to encourage more homeowners to get rid of their incandescent light bulbs. Compact fluorescents (CFL) could save consumers about $30 over the life of the bulb    because they use 75% less energy and last about 10 times as long as standard bulbs. According to the federal government's Energy Star program, if every owner replaced just one bulb in their home, enough energy would be saved to light more than 3 million homes for a year, save more than $600 million in annual energy costs, and prevent the emission of greenhouse gases equivalent to that of more than 800,000 cars.

Not quite on par with Chu's Tom Sawyer trick, but at least it's a workable idea.

At the end of the tunnel
According to research company Nielsen Claritas, 71% of consumers have at least one CFL installed in their home and 64% have two or more. Because Congress mandated that incandescents be eliminated by 2014, CFLs will be far more commonplace soon enough. Yet retailers such as Wal-Mart Stores (NYSE:WMT) and Costco (NASDAQ:COST) started the ball rolling already, and overall about 330 million bulbs are sold every year in the U.S. Even so, the Energy Department says that CFLs dropped to 21% of light bulb sales in 2008, down from 23% in 2007.

But in between the push for ecologically friendly devices and the market penetration of CFLs, there remains another opportunity -- solid-state light-emitting diodes, which are even better at saving energy than CFLs. LEDs, which are essentially tiny semiconductors, are twice as efficient and don't contain any of the mercury that CFLs do, so leaking harmful chemicals into the environment isn't a concern. CFL pollution has become a big-enough concern that Home Depot (NYSE:HD) started a bulb-recycling program last year.

Although you might want to dispose of LEDs in a manner similar to that of other electronic and computer components, their disposal is less of an issue, because they can last for decades.

That computes
The biggest market for LED lighting has been in commercial building applications, but computer backlighting has been gaining traction, and LED-backlit screens are predicted to become 30% to 40% of the notebook market in 2009.

LED chip maker Cree (NASDAQ:CREE) is looking to improve bookings -- specifically in the notebook backlighting area -- leading it to boost its guidance for its fiscal fourth-quarter revenue. And though the turmoil in the automobile market partially offset sales of LED components, the company was still able to increase revenue from that segment by 7% in the latest quarter. Earlier this year, Cree also forestalled similar problems.

Philips Electronics (NYSE:PHG), the world's largest lighting manufacturer, also anticipates a better market. It says the LED market has reached a trough, and it forecasts sales at its Lumileds division will increase 20% next quarter. And you can't count out General Electric (NYSE:GE), either. Its Lumination division is using LEDs to brighten supermarket display cases at Wal-Mart, and its officials say eight of the top 10 supermarkets in the U.S. are already using or testing its system.

Don't fight City Hall
Considering that the federal stimulus program includes billions for municipal infrastructure, we should begin to see cities and towns converting to LED lighting. San Jose, Calif., is using some of its $8.8 million in that stimulus spending to convert street lights to LEDs, similar to what Siemens' (NYSE:SI) Osram division is doing in Hamburg, Germany. Similarly, as part of its LED City initiative, Cree has convinced Raleigh, N.C.; Austin, Texas; and other cities to use and evaluate LEDs in street lamps, parking garages, and municipal offices.

If you're looking to profit from the future of lighting, there's really only one option. Cree is the closest thing to a pure play in the field and one of the best of the bunch, but at more than 98 times earnings, its stock looks richly valued now. Of course, I thought it was too high back in January when it traded at "just" 36 times forward estimates and I recommended that investors wait for a dip in the price that never materialized. It has nearly doubled in price since then (ouch!), but that doesn't help me recommend shares now. Any hiccups along the way and it would be lights-out for the stock.

But there are worse things you could be doing than waiting for a better price: Painting your roof, for instance.

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Costco, Home Depot, and Wal-Mart are Motley Fool Inside Value picks. Costco is a Stock Advisor recommendation, and the Fool owns shares of it. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Rich Duprey owns shares of Wal-Mart but does not have a financial position in any of the stocks mentioned in this article. You can see his holdings. The Motley Fool has a disclosure policy.