Residential Thermostat Usability: Comparing Manual, Programmable, And Smart Devices

Residential thermostats were originally very simple devices. Any energy saving practices, such as nighttime setbacks, were entirely dependent on the occupants and required diligent setpoint adjustment. Programmable thermostats were endorsed by Energy Star in the 1990s, but later studies showed they failed to realize expected savings due to a lack of usability. New, 'smart' thermostats promise to address the downfalls, while offering increasingly complex features. This study examines the relationship between thermostat usability and interface characteristics in Ottawa, Canada, with a focus on devices currently installed in homes. To compare manual, programmable, and smart interfaces, human computer interaction methods, including participant interviews and think-aloud analysis, were employed. A sample of 51 participants were interviewed in their homes and attempted six usability tasks on their thermostat interface(s). Interviews were recorded and each thermostat type (manual, programmable and smart) was evaluated based on the time to complete, required interactions and qualitative observations. An averaged time and success usability metric was assigned to each category and contrasted with previous literature. In general, smart thermostats were found to be significantly more useable than their programmable counterparts. Participants expressed a desire for more feedback regarding energy consumption and half (51%) noted they either wanted or enjoyed thermostat control through a smartphone application.