Residential Smart Thermostat Use: An Exploration Of Thermostat Programming, Environmental Attitudes, And The Influence Of Smart Controls On Energy Savings

Smart home technologies are becoming prevalent in residential buildings. Despite interface and control improvements offered by smart thermostats, previous work has found energy savings from this technology to be variable. Further, little is known about how smart thermostat operation differs from conventional programmable thermostat operation, which has been studied extensively. In this paper, data from 54 smart thermostats installed in two high-rise residential buildings are used to characterize smart thermostat programming and occupant interaction behaviours. Survey data are also used to examine how environmental attitudes and technical abilities influence thermostat usage behaviours. Smart thermostat programming rates were higher than those previously found for conventional programmable thermostats, likely due to improved thermostat interfaces. Further, programmed schedule accuracy was high (88% occupancy during scheduled unoccupied periods). Participants programmed substantial setforwards (cooling season average of 2.8 degrees C) and setbacks (heating season average of 3.8 degrees C) to be used when their home is unoccupied. Override behaviours were generally not problematic: most overrides had short durations or were frequently adjusted by users. Strong environmental attitudes and technical skills also appeared to result in more energy-conscious thermostat use behaviours, however, due to the population demographics, specific relationships between energy conservation attitudes and thermostat use behaviours were unclear. An analysis of thermostat schedules and setpoints considering measured occupancy data indicated that participant-programmed schedules achieved significant HVAC load reductions when compared to a scenario in which no schedule was programmed. Further, the use of occupancy-based controls, whether alone or in combination with a schedule, was shown to improve energy savings.(c) 2021 Elsevier B.V. All rights reserved.