Can Smart Thermostats Save Energy?

NEST thermostat reading 76 degrees installed on wall
“Smart” thermostats were installed in over 30 research homes.

Thermostats are the central switch that controls operation of heating and cooling systems—commonly the largest energy end use in homes. That energy setup/setback has potential for energy savings has been demonstrated repeatedly in well-controlled evaluations. Thus understanding how the occupants and thermostat interact is key to controlling energy use. Programmable thermostats have often been bypassed by occupants. Newer “smart” thermostats get around these problems by self-programming depending on heuristic or machine learning evaluation of user control habits as well as sensed occupancy. These modern devices use a combination of data on occupancy, weather, and thermostat-setting preference to help consumers with automated setback/setup schedules.

Researchers at FSEC installed smart thermostats, primarily the Nest Learning Thermostat, in more than 30 research homes. A full year of sub-metered hourly temperature and heating and cooling system operation data were available prior to the installation of the smart thermostat allowing detailed evaluation of temperature-related changes. Overall measured heating and cooling energy savings averaged 9.5% with some significant variation among homeowners.

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Evaluation of the Space Heating and Cooling Energy Savings of Smart Thermostats in a Hot-Humid Climate using Long-term Data*

 

*This paper was presented at the 2016 ACEEE Summer Study on Energy Efficiency in Buildings in Pacific Grove, CA on August 22 -26, 2016.

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FSEC Research Presented at 2014 ACEEE Summer Study on Energy Efficiency in Buildings

FSEC researchers presented their research findings at the 2014 ACEEE Summer Study on Energy Efficiency in Buildings in Pacific Grove, CA on August 17-22, 2014. Check out their research publications:

3D view of exhaust fan
One study met ASHRAE 62.2 levels of ventilation with a high quality, quiet exhaust fan rated for continuous runtime, with an insulated exhaust duct to limit condensation.

What are the implications of mechanically introducing humid outside air into residential buildings, compared to the indoor air quality benefits?

Take a look at the results of a study of 10 homes in Gainesville, FL that includes impact on energy use, comfort, durability, and cost.

 

In another study of mechanical ventilation in homes, two lab homes, constructed to represent characteristics of typical existing Florida homes, were monitored. They were configured with tight and leaky building envelopes, and with and without mechanical ventilation. Simulation results of high performance new homes with mechanical ventilation, and typical older homes with and without air tightening and mechanical ventilation, were also presented.

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