That means companies such as Cree could be seeing green, too.

The Durham company and its 1,350 local employees make tiny, long-lasting devices called LEDs that put out light using very little energy. Today, some of the largest markets for LEDs are in cell phone displays and keypads, car dashboards and traffic lights.

But an endorsement by the world's largest retailer could help the devices make the leap from mobile phones to lighting homes.

Although LED manufacturers are gunning for widespread acceptance, consumers frequently adopt technology after businesses do, said Seth Dadds, an analyst who follows Cree for Garp Research Securities in Baltimore.

That's where Wal-Mart comes in. After 16 months of trials at two experimental stores, the world's largest retailer has decided to install freezers equipped with LED lights in all of its new Sam's Club and Wal-Mart stores, starting in January.

What's special about LEDs: The tiny devices use just a fraction of the power of conventional light bulbs and can run for years, decades even, without burning out. For stores and families, that means lower power bills and rarely having to change light bulbs.

The drawback: The price. LEDs cost less over the long run, but they require a bigger initial investment than incandescent or fluorescent light bulbs.

But costs have been dropping, even as brightness increases. Wal-Mart's endorsement shows that businesses now can make a financial argument for adopting LED technology, Dadds said.

And when the price gets low enough, the consumer markets will follow, he said. "As with anything, you start with niche applications and move from there."

The big deal about Wal-Mart: When the world's largest retailer endorses something, other businesses notice. The retail giant has a reputation as a trendsetter when it comes to technology, efficiency and logistics.

"This will bring much-needed attention to a technology that's been available but hasn't necessarily caught on the way it should," said Joel Makower, founder and executive editor of GreenBiz.com, a group that provides resources for businesses on environmental responsibility.

Is Wal-Mart using Cree's LEDs? It's hard to say. Cree has worked with all major freezer companies, including those serving Wal-Mart, but can't be more specific about its alliances, said Mark McClear, director of business development.

Meanwhile, rival LED manufacturer Nichia signed a deal with Gelcore, a division of GE. Gelcore, in turn, has a deal to supply 500 Wal-Marts with LED lighting for refrigerated display cases.

Where else are Cree's LEDs showing up: Cree's LEDs recently arrived on the market in flashlights, light fixtures for parking garages and recessed lights for homes. They're also illuminating the outside of buildings, signs and light fixtures for spas and swimming pools.

Within the next two years, the company's products will be lighting up the sales floor, as well, McClear said. "Retail lighting in general has huge potential for LEDs," he said.