Thermostat settings that save energy without sacrificing comfort

Setbacks: the main way to save

A setback means letting the temperature drift lower in winter, or higher in summer, during hours when nobody needs full comfort. DOE’s Energy Savers guide says you can save as much as 10% a year on heating and cooling by turning the thermostat back 7 to 10°F for 8 hours a day.

The common myth is that the system uses more energy “catching up” afterward than it saved. It does not: a house loses heat more slowly when it is cooler inside, so the longer the setback, the more you save. The two natural windows are overnight and while everyone is out.

ENERGY STAR’s maintenance checklist makes the same point: check your settings so the system keeps you comfortable when you are home and saves energy when you are away.

If you have a heat pump

Heat pumps need more care with setbacks. DOE says not to set back a heat pump’s thermostat manually if it causes the electric-resistance heating to come on. A big jump in the setting on a cold morning can bring on the auxiliary (backup) heat, which costs much more to run and can wipe out the saving.

• Use small setbacks, or none, in very cold weather.
• Many thermostats made for heat pumps raise the temperature gradually to avoid backup heat. Ask your installer whether yours does, and how it is set up.
• “Aux” on the display means backup heat is running; "Em heat" is a setting for when the heat pump has failed, not for everyday use.

More on how heat pumps behave in cold weather is in our heat pump guide.

Programmable vs smart thermostats

You can make setbacks by hand, but most people forget. Two kinds of thermostat do it for you:

• Programmable: you set a schedule for weekdays and weekends once, and it follows it. Simple and reliable, as long as you actually program it.
• Smart: a smart thermostat connects to Wi-Fi so you can adjust it from your phone, and many can learn your routine or notice when everyone has left. Some need a C-wire for constant power – check before you buy.

Either type only saves energy if the schedule includes real setbacks. If you have a heat pump, dual-fuel system or multi-stage equipment, make sure the thermostat supports it, and consider having it wired by a technician.

Fan: Auto or On?

• Auto runs the blower only while the system is heating or cooling. This suits most homes and uses the least electricity.
• On runs the blower all the time. It mixes air between rooms and passes more air through the filter, but uses more electricity. In summer it can also blow moisture from the wet cooling coil back into the house before it drains away, which can make rooms feel muggy – see the indoor humidity guide.

Some thermostats offer a “circulate” mode that runs the fan part of each hour, a middle ground if some rooms feel stuffy.

Where the thermostat is matters

A thermostat reads the temperature where it sits. If that spot is unusual, the whole house follows a wrong reading. Keep it:

• On an interior wall, in a room you use often.
• Out of direct sunlight.
• Away from drafts, exterior doors and windows.
• Away from supply vents, lamps, ovens and other heat sources.

If one room is always hot or cold while the thermostat’s room is fine, the cause is often airflow or ducts rather than the setting. Moving a thermostat means rewiring; it is a job for an electrician or HVAC technician.

Settings while you are away

• Use a longer setback or the thermostat’s vacation or hold mode, and set it back to normal shortly before you return. A smart thermostat lets you do that from your phone.
• Winter: do not turn the heat off entirely in freezing weather – pipes can freeze and burst. Keep the house warm enough to protect plumbing, and ask someone to check on it if you will be gone long.
• Summer: in humid climates, turning the AC fully off for a long trip can let moisture build up. A higher setting keeps some dehumidification going.
• Pets and plants still need a livable temperature.

What not to do

• Cranking it up or down to heat or cool faster. Most systems deliver heat or cooling at the same rate however far you move the setting. A bigger jump just makes the system run past the temperature you actually wanted, wasting energy. With a heat pump it can also call for costly backup heat.
• Fighting the schedule. Constant manual overrides cancel out the saving.
• Closing lots of vents to “save” on unused rooms. It can upset the airflow the system was designed for.
• Ignoring a thermostat that seems off. If the reading and the room do not match, check placement and batteries before blaming the equipment.

Sources

• DOE: Energy Savers guide (DOE/GO-102011-3291, December 2011, PDF) (checked October 2026)
• ENERGY STAR: HVAC Maintenance Checklist (checked October 2026)