Buildings are responsible for 40% of total annual U.S. energy consumption. Over $80 billion dollars are spent every year on electricity and natural gas in buildings. Lighting alone comprises nearly a quarter of a building's total energy consumption. The lifespan of a typical non-residential building is over 75 years, while public schools have a useful life of about 60 years. Therefore energy costs accumulate enormously over time and can easily surpass the initial cost of the building itself
