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A Case for Thermostat User Models

A Case for Thermostat User Models. Bryan Urban and Carla Gomez Fraunhofer Center for Sustainable Energy Systems Cambridge, MA, USA email: burban@fraunhofer.org. Misconceptions of Thermostats. An on/off switch A dimmer switch An accelerator

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A Case for Thermostat User Models

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  1. A Case for Thermostat User Models Bryan Urban and Carla Gomez Fraunhofer Center for Sustainable Energy SystemsCambridge, MA, USA email: burban@fraunhofer.org

  2. Misconceptions of Thermostats • An on/off switch • A dimmer switch • An accelerator • Turning down the thermostat has little or no effect on energy consumption http://www.forwardthinking.honeywell.com/products/thermostats/thermostat_products.html

  3. How People Use Thermostats • Overrides • Temporary override • Long-term override • Permanent hold • Use to turn heating system on and off • Leave on and open windows • 20% are set to the incorrect time http://www.forwardthinking.honeywell.com/products/thermostats/thermostat_products.html

  4. Field Study • 82 apartment units tested • Installed • Programmable thermostats • Temperature/RH sensors • Furnace state sensors • 60 units provided adequate feedback http://www.revereha.org/Liston-Towers.html

  5. Fixed Setpoints Schedules Infrequent Override Frequent Override

  6. Fixed Setpoints Schedules 72.2 °F 71.0 °F Infrequent Override st. dev. 2.8 °F st. dev. 2.6 °F 73.0 °F 71.3 °F Frequent Override st. dev. 4.7 °F st. dev. 5.0 °F

  7. Fixed Setpoints Schedules 77 therms 26 therms Infrequent Override st. dev. 58 st. dev. 14 76 therms 75 therms Frequent Override st. dev. 32 st. dev. 56

  8. Conclusions • Misconceptions about thermostats lead to unexpected usage patterns • Behavioral differences lead to large variation in energy consumption • ASHRAE 90.2 did not accurately describe real setpoints or schedules • Existing energy modeling tools can model behavioral variability in thermostat schedules

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