NEW YORK - NOVEMBER 08: New York City Mayor Michael Bloomberg rides the subway after voting on election day November 8, 2005 in New York City. According to a recent poll, Bloomberg has a 38-point lead over Democratic mayoral challenger Fernando Ferrer. (Photo by Spencer Platt/Getty Images)
The billionaire mayor says he also turns off lights that aren't being used and likes to open windows when it is warm instead of using air-conditioning.
In addition to a Manhattan townhouse, Bloomberg owns homes in upstate New York, Colorado, Florida, Bermuda and London.
Bloomberg had sought to cast himself as a national environmental leader when he was testing his appeal as an independent presidential candidate for 2008.
He acknowledges that he uses a lot of energy, but tries to "make it as little as possible."