Nordstrom Inc. is doing something cool to keep its customers comfortable in the tropics.

The luxury retailer is producing 43 tons of ice every night in giant metal cylinders on top of its long-awaited, first full-line store in Hawai'i.

The 210,000-square-foot department store that opened this month is the only one in the company's 103-store chain with an ice cooling system.

Nordstrom wouldn't say how much it cost to install, only that it was 50 percent more expensive than a traditional air-conditioning system. In addition to the pricey equipment, builders had to install extra steel beams to support the weight of the ice.

"It's a big investment," said Brooke White, a spokeswoman for the Seattle-based company. "It made sense from a cost standpoint, as well as being a good neighbor."

The store expects to save on its utility bills in the long run while reducing its environmental impact.

Nordstrom said the three-story store will use about half the electricity of a similarly sized retailer during daytime hours.

The ice-cooling technology is used in several buildings across the nation, but the high up-front cost discourages wider use. In balmy Hawai'i, it's used by a handful of businesses, hospitals and schools.

'Iolani School was the first in the state to install the system in 1995. Five years ago, the private school expanded its ice chiller system to all of its classrooms and buildings on the 25-acre campus across the canal from Waikiki.

"Overall, it's working really, really well," said Cathy Lee Chong, a spokeswoman for the school. "It saves us a lot of money in energy costs and it allows us to go off the (power) grid."

The school also received a state tax credit, which doesn't exist anymore.

According to Hawaiian Electric Co., Costco Wholesale Corp. also uses the technology at its Iwilei store, the warehouse retailer's top-selling location in the nation.

The system recharges or creates the ice at night during off-peak energy hours. But the technology is not as simple as producing ice cubes at night and leaving the freezer door open in the day.

Nordstrom has four dozen 1,700-gallon thermal tanks on the roof of its store, where the ice is created and stored. It almost looks like a small brewery with all the metal cylinders.

A glycol-water solution is chilled to 20 degrees and passes through hoses in the storage tanks, freezing the water.

As the ice melts during the day, it keeps the solution cool, which is sent through pipes where fans send chilly air into the store. The fans adjust accordingly to the temperature in the store.

Nordstrom is monitoring the system to possibly expand the technology to other states but has no immediate plans for additional installations.

In a conventional system, compressors work the hardest during the day when it's the hottest. For large retailers in Hawai'i, the air conditioning is just as critical as lights.

While the state's tax credits have expired, the local utility is giving Nordstrom a credit of 3 cents per kilowatt hour during nighttime hours when the retailer is creating the ice, HECO said.

"This is the kind of technology which will shift the amount of energy to a time of day where it's not going to have as much impact on the rest of the electric system," utility spokesman Darren Pai said.

That should save thousands of dollars annually, especially in Hawai'i, which has the highest electricity prices in the nation and is dependent on oil more than any other state.

Nordstrom is the latest retailer looking to go green in Hawai'i to save some cash.

Costco, in addition to its ice cooling system, recently installed solar-electric systems atop two of its stores in Hawai'i. Wal-Mart in January unveiled a large solar-power system on the roof at its double-decker, megacomplex in Honolulu that features a Sam's Club on top of a Wal-Mart.

Wal-Mart plans solar systems for 22 stores in Hawai'i and California as a pilot project for possible expansion to other areas.