According to International Dark-Sky Association, "In an average year in the U.S., outdoor lighting uses some 120 terawatt-hours of energy, mostly to illuminate streets and parking lots. That’s enough energy to meet New York City’s total electricity needs for 2 years. Unfortunately, up to 50 percent of that light is wasted. That adds up to $3.3 billion and the release of 21 million tons of CO2 per year! To offset all that CO2, we’d have to plant 875 million trees annually."