Heating and cooling
Thermostat settings for furnaces and heat pumps, fans, window air conditioners, ducts and space heaters.
Free
- Turn a furnace or boiler thermostat down 7 to 10°F for 8 hours a day
DOE says turning a furnace or boiler thermostat down 7 to 10°F for 8 hours a day in fall and winter can save as much as 10% a year on heating and cooling.
- Hold a heat pump steady instead of setting it back at night
ENERGY STAR says a heat pump does not save energy when turned down. Hold one setting in Heat mode; a cold-climate unit is rated at a COP of at least 1.75 at 5°F.
- In summer, a fan saves only when you raise the thermostat about 4°F
DOE says a ceiling fan lets you raise the thermostat about 4°F without any loss in comfort. In summer, raise it while the fan runs, and turn the fan off when you leave.
- An electric space heater saves only if the rest of the house gets colder
A 1,500-watt space heater uses 1.5 kWh an hour, about 27 cents at the July 2026 US average. It pays only if turning down the central heat saves more than that.
Small buy
- Size a window AC by square feet, then adjust for sun and shade
ENERGY STAR sizes a window AC by floor area: 6,000 BTU/h for 150 up to 250 sq ft. Take 10% off for heavy shade and add 10% for a very sunny room.
Bigger job
- Seal ducts with mastic or metal foil tape, never duct tape
ENERGY STAR: a typical house loses about 20 to 30% of its duct air to leaks, holes and poor connections. Seal reachable joints with mastic or foil tape, never duct tape.