Smart Thermostat Settings That Save Energy

Heating and cooling are the biggest line on the bill.

ENERGY STAR says that for the average American household, almost half of the annual energy bill goes to heating and cooling — more than $900 a year. The thermostat controls that half. Leaving it at one constant temperature, ENERGY STAR’s heating and cooling guide notes, misses the chance to lower the setting during the hours you are regularly away or asleep.

Four periods a day, as a starting point.

The table is from ENERGY STAR’s guide to energy-efficient heating and cooling, written for programmable thermostats and meant as a starting point to adjust for comfort. With a manual thermostat, the guide says adjusting 5 to 8 degrees, down in winter and up in summer, can save energy if you will be away for several hours.

Long setbacks, few overrides.

• Keep the energy-saving setting for long stretches, such as the workday and overnight.
• Use the hold setting at an energy-saving temperature for a weekend away or a vacation.
• Resist overriding the schedule; ENERGY STAR notes every override uses more energy.
• Use a separate thermostat for each zone if the house has more than one.
• Change batteries yearly in battery-powered models.

Where the thermostat is mounted matters as much as the setting. Install it on an interior wall, away from heating and cooling registers, appliances, lighting, doorways, fireplaces, skylights, windows, direct sun, and drafts; a sensor in a sunny or drafty spot runs the whole house by the wrong reading. See a thermostat that will not reach its setting for diagnosis.

Certified on real homes, not lab claims.

ENERGY STAR describes a smart thermostat as a Wi-Fi enabled device that automatically adjusts heating and cooling settings. Certified models are third-party tested on field data from more than a thousand homes over a whole year, enter a low-power standby mode when inactive, and report equipment use and temperature data to the homeowner. Common features: control from a smartphone, geofencing that adjusts the temperature as you leave or head home, learning your preferences to build a schedule, and periodic software updates. The savings still come from setbacks; the features make them happen without your remembering.

Compatibility, Wi-Fi, heat pumps, rebates.

ENERGY STAR’s buying tips: make sure the thermostat is compatible with your heating and cooling system; for the highest-efficiency equipment, such as an air conditioner rated 20 SEER or higher, you may want a controller from the same company; and keep a Wi-Fi model reasonably close to the router to avoid disconnections. If you have a heat pump, the heating and cooling guide says you may need a special thermostat to save energy year-round, so ask your contractor; see heat pump or furnace. Utilities or efficiency programs may offer rebates on certified models, findable at energystar.gov/rebatefinder, and some pay smart thermostat owners to join programs that support the grid. Tightening the house first makes every setting cheaper; see air sealing before insulation.