A new Wal-Mart Supercenter in Las Vegas is its most efficient yet and cuts energy use by 45%.

The store features heat-soaking floors that will help cool the 210,000-sq.-ft. interior. Pipes run through the concrete floors every six inches and carry cold water from indirect evaporative coolers on the roof, keeping the floor temperature at 67-68 degrees.

The cooling towers run water through hundreds of black, engineered polymer tubes less than the diameter of a pencil, rather than more expensive copper tubing. The indirect evaporative cooling system will provide 80% of the cooling at the store, said James McClendon, Wal-Mart's engineering director.

Also, hot exhaust air from refrigerated food displays will be used to heat the store during winter and to heat water for the store year-round.

McClendon believes the new energy conservation system will pay for itself through lower power bills within four years.

The Vegas store is the first complete Wal-Mart Supercenter to contain these energy-conservation systems, although the company tested the floor-cooling system in a portion of a store in Sacramento, Calif.

Wal-Mart technicians will be monitoring the cooling and lighting systems at the new store remotely through computers in Bentonville, Ark. The company will share data with the Department of Energy, the National Renewable Energy Lab in Denver and the University of California, Davis.

The energy system is specifically designed for hot dry, climates. If the Vegas store proves to be as energy-efficient as McClendon expects, other new Wal-Mart stores in the Southwest probably will use similar technologies.

"It's one of our stated goals to share this information," McClendon said. "We're all in this together."