Exploring smart thermostat users' schedule override behaviors and the energy consequences

Programmable thermostats with frequent schedule overrides (i.e., holds) are widely assumed to be detrimental to potential energy savings. We explored whether this assumption generalized to a population of smart thermostats using a longitudinal dataset of 20,000 devices from a single manufacturer. We observed a majority of devices were infrequently overridden, most often to less energy-efficient setpoints; nonetheless, the short duration of each override resulted in minimal increase in energy use. When we instead looked at the minority of thermostats consistently overridden (accounting for approximately 12% of the thermostats), we observed that a large fraction were being repeatedly manually adjusted, but often in an energy saving manner yielding energy performance on par with rarely overridden thermostats. Only the consistently overridden but infrequently adjusted population of thermostats showed poor energy performance, but these accounted for less than 5% of thermostats with energy performance roughly 2% worse on heating and 4% worse on cooling than the remaining population. While there may be effective ways to modify thermostat user interfaces to dissuade users from long-duration energy-inefficient hold settings, we conclude from our study of smart thermostats that user holding behavior may not be as detrimental to collective energy savings as commonly believed.