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An international peer-reviewed journal

Making Energy Savings Easier: Usability Metrics for Thermostats

Daniel Perry, Cecilia Aragon, Alan Meier, Therese Peffer, and Marco Pritoni

Journal of Usability Studies, Volume 6, Issue 4, August 2011, pp. 226 - 244

Article Contents


Federal agencies such as the EPA and DOE, and programs such as EnergyStar™, are beginning to realize the impact that usability can have in achieving the nation’s energy savings goals. However, manufacturers of thermostats and other appliances are unlikely to accept non-quantitative standards for usability, and there does not yet exist such a standard metric in this domain. To this end, we developed a novel set of usability metrics specific to PTs, which could also be used on other embedded devices. Via a formal usability study of five thermostat models, we demonstrated that the metrics are effective at distinguishing devices based on usability and are highly correlated with each other—NIST, the industry standard, and with an expert’s subjective usability evaluation utilizing standard heuristics. Additionally the metrics are normalized to the interval [0, 1], enabling an objective standard across devices while offering manufacturers and organizations several different options for evaluating interface usability.

We have submitted these metrics to the EPA’s EnergyStar™ program with the goal of facilitating the uptake of usability engineering principles among manufacturers of thermostats, appliances, and other embedded devices. Ultimately, we hope to make a contribution to sustainability by contributing to the design of better tools that will enable individuals to make informed choices on issues such as reducing energy consumption.


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