Lighting and heating, ventilating, and air conditioning (HVAC) for residential buildings account each for approximately 20% of total U.S. electricity use. Refrigerators represent another important energy end use in the U.S. residential sector, with about 16% of electricity. In several countries where residences are o¬en not air conditioned, electrical systems, including lighting and appliances, can represent over 80% of the total energy used in a typical home.