The Nest Learning Thermostat earned an ENERGY STAR from the EPA. After rigorous testing, the EPA has confirmed the Nest Thermostat saves energy. Independent studies have shown that the Nest Thermostat has saved people an average of 10% to 12% on heating bills and 15% on cooling bills. Based on typical energy costs, estimated average savings are $131 to $145 a year, so in under two years, it can pay for itself.
Nest | http://www.nest.com