Olga Sachs and Kurt Roth

Programmable Thermostats: Does Usability Matter for Energy Savings?

Programmable thermostats have become notorious for how difficult they are to use. A large proportion of the population cannot use them effectively, partly because the interface design of this product is not intuitive for non-technical users (Peffer et al., 2011). Laboratory usability tests for five different programmable thermostats (Meier et al., 2011) revealed that usability varies greatly across various existing models. However, it is largely unknown what impact thermostat usability has on heating and cooling energy consumption in households – no field tests have directly evaluated energy savings achieved in actual households due to increasing usability of programmable thermostats. To fill this gap, researchers from Franhofer deployed high and low-usability thermostats, as evaluated by LBNL, in a 94-unit multi-family building in the Boston area. Researchers randomly assigned residents of the building to two experimental groups: the high- and low-usability thermostat groups. To infer occupant behavior regarding thermostat use, we installed sensors to monitor indoor temperature and HVAC use over a five-month period. They used this data to infer user interaction with the thermostats and to find out whether building occupants in the high-usability thermostat condition are more likely to set back their thermostats at night to save energy.

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