When it comes to creating wintertime comfort with a thermostat, the calculations would seem to be pretty straightforward: factor in the building occupants’ notion of comfort and what they’re willing to pay to heat the building interior to satisfy those notions, then set the thermostat accordingly and be done with it.
Simple. But it turns out that process tells us some things about occupant behavior that really aren’t so straightforward. Utility usage data collected and analyzed by EnergyHub, a Brooklyn, New York-based specialist in energy conservation tools and strategies for homeowners, showed that the correlation between occupants’ geographic location and their average wintertime thermostat settings didn’t match expectations. Residents in northern states, it turns out, tend to set their thermostats lower in the winter than residents in southern states, despite the usual differences between the two regions in average outdoor temperatures.
The analysis revealed, for example, that residents in Vermont, which has an average of 7,746 heating degree days a year, set their thermostats at 63.4 degrees, while residents in Texas, which has 1,862 heating degree days a year, set their thermostats at 69.9 degrees. (EnergyHub collected the data from its smart thermostat software platform, Mercury, which is designed to allow residents to control interior temperatures while factoring in a range of energy-saving strategies, including daytime and nighttime temperature preferences as well as costs per degree.)
A tolerance for cold?
EnergyHub suggests that people who live in cold-climate states tolerate lower ambient indoor temperatures because they’ve adapted to the cold. Or, as one recent Greentech Media post noted, they are simply accustomed to wearing sweaters and other layers of clothing during the winter months.
Very likely, too, cold-climate residents, many of whom rely on oil heat (while Texans rely on gas, which is less expensive), are mindful of the high cost of setting the thermostat much above 65 degrees.
There may be other issues at play here as well. One commenter to the Greentech Media item noted that many dwellings in both Vermont and Maine are owned by vacationers who have equipped their homes with remotely controlled thermostats that they set at 50 degrees in wintertime, when the buildings are usually unoccupied.
GBA editor Martin Holladay offered another theory. Many Vermont homes have wood stoves in addition to central heating. Even when a thermostat is set at 60 degrees, he points out, a wood stove can still warm a house to 72 degrees.