As the summer swelters on, skyscrapers and apartments around the city will be cranking up the air conditioning and pushing the city's power grid to the limit. But some office towers and buildings have found a way to stay cool while keeping the AC to a minimum - by using an energy-saving system that relies on blocks of ice to pump chilly air through buildings. The systems save companies money and reduce strain on the electrical grid in New York, where the city consumes more power on hot summer days than the entire nation of Chile. It also cuts down on pollution. An ice-cooling system in the Credit Suisse offices at the historic Metropolitan Life tower in Manhattan is as good for the environment as taking 223 cars off the streets or planting 1.9 million acres of trees to absorb the carbon dioxide caused by electrical usage for one year. Such a reduction in pollution is valuable in a city where the majority of emissions come from the operation of buildings. State officials say there are at least 3,000 ice-cooling systems worldwide. "It is worth it to do in New York City," said William Beck, the head of critical engineering systems for Credit Suisse. "If you take the time to look, you can find innovative ways to be energy efficient, be environmental and sustainable." Because electricity is needed to make the ice, water is frozen in large silver tanks at night when power demands are low. The cool air emanating from the ice blocks is then piped throughout the building more or less like traditional air conditioning. At night the water is frozen again and the cycle repeats. Ice storage can be used as the sole cooling system, or it can be combined with traditional systems to help ease the power demands during peak hours. At Credit Suisse, for example, the company must cool 1.9 million square feet of office space at the Met Life tower, a historic building that was New York's tallest in the days before the Empire State Building. In the basement, three main cooling rooms house chilling machines and 64 tanks that hold 800 gallons of water each. Credit Suisse has a traditional air conditioning system, but engineers use the more efficient system first. Construction on the system took about four months, and company engineers say it is extremely efficient. "The concept is the same, but when you make something mechanical, it can break, but a big block of ice four floors below grade level isn't going to do anything but melt," said Todd Coulard of Trane Energy Services. The company built the Credit Suisse system and is one of several that work with ice storage. Trane, the air-conditioning arm of American Standard, also developed a system for Morgan Stanley's Westchester County offices, and just completed a new system for its offices on Fifth Avenue. A new Goldman Sachs headquarters will also have ice cooling. Credit Suisse is looking at installing the systems in offices around the globe, but nothing has been decided yet. Coulard, an expert in energy efficiency, was hired by the company four years ago to develop the energy services department. "I've been doing green since before it was cool," he said. "The idea of not only saving money for large companies, but doing something that benefits the environment is win-win. It's doing the right thing." Engineers say the power-saving results from the system are impressive. And it translates into millions of dollars saved in energy bills for the companies. Ice storage at Credit Suisse lowers the facility's peak energy use by 900 kilowatts, and reduces overall electric usage by 2.15 million kilowatt-hours annually - enough to power about 200 homes. At the Morgan Stanley facility in Westchester County, the system reduces peak energy use by 740 kilowatts and overall electricity usage by 900,000 kilowatt hours annually. Both companies received incentives from the New York State Energy Research and Development Authority under a program designed to improve the power grid and help businesses reduce operating costs. The technology isn't for every office space. There has to be room to install the large tanks. And costs are considerable: Credit Suisse spent more than $3 million to renovate its cooling system; and Morgan Stanley's costs were comparable, which means the technology is best suited to large companies. "This is for companies that want to go green but that there has to be other benefits, returns on investments," Coulard said. "It works for larger companies because their cooling costs are so considerable."