The first green retrofit of the Empire State Building, completed in 2010 and costing slightly over $31 million, was pioneering for its time. Aside from the rebuilding of the chiller plant, each of the building's 6,514 windows received an extra pane of coated film to assist minimize heat gain in the summer and heat loss in the winter. The building also uses 20% less electricity than before. The second green retrofit of the Empire State Building is scheduled for completion in 2015. It will reduce energy usage by another 20%. The new features include solar-powered shades for all windows, more efficient heating and cooling systems, and high-efficiency lighting. Also, the building will be completely off the power grid! Conventional skyscrapers need to use a lot of energy to keep their temperatures even. The majority of this energy is used for air conditioning. Green buildings are designed to use less energy because they're located away from major traffic arteries, they have better insulation, and they employ environmental design strategies such as daylighting and ventilation. The Empire State Building is one of the most famous green buildings in America and has been called "the world's best example" of an environmentally friendly structure. It's not only green, it's also one of the most expensive buildings to rent!