NEW YORK (CNNMoney.com) -- The Empire State Building kicked off a major energy-saving retrofit Monday, and promoters hope one of the world's most iconic skyscrapers can become an efficiency model for buildings worldwide. From the cloud-shrouded observation deck on the building's 80th floor, former President Bill Clinton, New York City Mayor Michael Bloomberg and others detailed $20 million in cutting-edge conservation measures they hope will cut energy use by 38% for the 1930's-era behemoth. They stressed the retrofits weren't green altruism or part of a government program. Instead, they say they're being done simply to save the building's owners a lot of money.