NEW YORK (AP)  -- New York City has switched on its first trigeneration power plant, a novelty expected to cut both pollution and electric bills for residents of a giant Bronx apartment complex.

The new Co-Op City plant went into action Thursday. The city spent $65 million transforming the plant from a heavy polluter into what officials call a model of efficiency and environmental friendliness.

Burning oil or natural gas to generate electricity produces heat. Traditional plants just emit it. The new Co-Op City plant harnesses that heat for heating, cooling and turning turbines to glean more electricity.

The city says the change will save the complex's 55,000 residents a total of $15 million to $25 million a year. Officials say it also will lower pollution and carbon dioxide emissions by 40 percent.