This page of the ENERGY STAR website provides all the documents describing the requirements and manufacturer commitments for the certification of connected thermostats. Smart thermostats were added to the ENERGY STAR certification programme in January 2017. In order to get the certificate, manufacturers are required to provide heating and cooling data from at least 1,000 homes collected for over a year from across the United States. A minimum threshold of energy savings has to be met compared to a baseline home, i.e. 8% for heating and 10% for air-conditioning.