What temperature to set your thermostat to save money

Winter: the numbers from the Department of Energy

The Department of Energy says you can save energy in winter by setting the thermostat to around 68–70°F while you are awake and setting it lower while you are asleep or away. It adds that you can save as much as 10% a year on heating and cooling by turning the thermostat back 7–10°F for 8 hours a day from its normal setting. Savings are greater for homes in milder climates than in severe ones, because the system has more time at rest.

A starting schedule for a typical weekday:

The 60–62°F figures are simple subtraction from 68–70°F, not a rule: check what is comfortable for your household. Infants, older adults and anyone with a health condition may need a warmer floor; follow medical advice.

Summer: raise the setting and add air movement

The Department of Energy says running your air conditioning at 78°F instead of 72°F can save between 6% and 18% on your cooling bill. It also notes that a ceiling fan lets you raise the thermostat setting about 4°F with no loss of comfort. Fans cool people, not rooms, so turn them off when you leave. When you are away, set the thermostat warmer than normal.

What setback depth and timing really do

The savings come from the difference between your setting and the outdoor temperature. The bigger the gap, the faster the house loses heat, so a lower setting always loses less than a higher one. The system then works to recover. That is why recovery time matters more than the exact number: set the schedule so the house is back to your comfort temperature when you wake up or come home. A smart thermostat learns the lead time, and most programmable models can be set to start early.

• Short absences (1–2 hours): setbacks save little and may not be worth it.
• Work days or overnight: the sweet spot, 6–10 hours.
• Several days away: set a wider setback, but keep the house from freezing. Pipes in unheated spaces can be at risk in cold weather; a freeze alert sensor adds a warning.

Heat pumps and electric resistance heat

This is where a setback can backfire. The Department of Energy says setting back a standard programmable thermostat is generally not recommended with heat pumps, because the system may run inefficiently and cancel the savings, and that maintaining a moderate setting is the most cost-effective practice. Some manufacturers offer thermostats designed for heat pumps. The Department of Energy also says that today’s heat pumps can reduce electricity use for heating by up to 75% compared with electric resistance heat, which is why keeping a heat pump running steadily is usually the right strategy. See smart thermostats for heat pumps for the wiring and auxiliary heat details.

Myths that cost money

• “Setting it to 80°F heats the house faster.” Many homes have a single-stage heating system that runs the same way whatever the target, so a higher number just runs longer and overshoots.
• “It uses more energy to reheat than to maintain.” The house loses more heat at the higher temperature, so a setback of several hours still saves. The exception is a heat pump with auxiliary heat, as above.
• “Smart thermostats save energy on their own.” They save through the settings they apply. ENERGY STAR reports an average of 8% on heating and cooling, about $50 a year, for certified models. Estimate your own with the smart thermostat savings calculator.

Humidity and comfort

Temperature is only part of comfort. The EPA advises keeping indoor humidity below 60%, ideally between 30% and 50%, to limit mold growth. In summer, air that is cooler and drier feels more comfortable at a given temperature; in winter, a very cold house can lead to condensation on windows and cold walls. If one room is always too warm or too cold, a separate room sensor or a damper issue is likely: see room sensors for uneven temperatures.

Let the thermostat do it

The settings are easy to choose and hard to keep. A smart or programmable thermostat applies them on a schedule, and a smart one can add away detection and occupancy sensing. See smart vs programmable thermostat for what each adds. Your local rules matter too: in a rental, check your lease and local rules before you change the thermostat, and ask about minimum heating requirements if you are leaving the unit empty.