How Much Does It Cost to Run a Whole-House Fan per Day?

Source: Planning watts of 400 and 8 hours a day, hours of running time a day when outdoor air is cooler than indoor air. Price: 17.23 cents per kWh, the 2025 US residential average from EIA Form EIA-861.

The monthly cost is 11% of the $150.68 average US electric bill. Because it runs only about 4 months a year, the yearly cost is 4 times the monthly figure, not twelve.

One figure cannot fit every home. These three cases show how much the answer moves with the equipment and the hours.

The lowest case costs $6 a month and the highest $37. Use the calculator above to match your own.

The same whole-house fan costs different amounts depending on the state, because the price per kWh differs. Here are the three cheapest states, the US average and the three costliest, for the same 97 kWh a month.

Source: U.S. Energy Information Administration, Form EIA-861 (final 2025 data). Price is residential revenue divided by sales and includes fixed charges.

See electricity rates in every state to find your own.

A whole-house fan pulls cooler outside air in through open windows and pushes warm air out through the attic. It uses much less power than air conditioning, but it only works when the outdoor air is cooler than the air inside.

Fan size and speed set the draw, and the climate sets the hours. It suits places with cool evenings. In very humid or very hot nights it does not help much.

The range for this kind of appliance runs from about 120 to 700 watts. At 8 hours a day that is $5 to $29 a month, which is why checking the label on yours is worth the minute.

• Run it in the evening and overnight when the outside air is cooler than the house.
• Open enough windows to give the fan air, as the maker advises, and close them in the morning.
• Cover or seal the fan in winter to stop heat escaping through the ceiling.

Next step: Central air conditioner costs. For general ideas, read how to lower your electric bill.

Other appliances in the cooling group: Air Conditioner, Window Air Conditioner, Central Air Conditioner, Portable Air Conditioner, Ceiling Fan, Mini-Split Heat Pump.

The cost is watts divided by 1,000, times hours, times your price per kWh. The 400 watts is a planning figure for this kind of appliance, set from typical product ratings, and the 8 hours is an assumed day of use. Neither is copied from a federal table. Federal guidance describes the method and warns that real wattage varies, so we publish our own typical ranges and label them as such. Prices come from EIA Form EIA-861 for 2025.

The calculation is the standard one used in the U.S. Department of Energy's consumer guidance on estimating appliance energy use. Wattage varies by product age and features, so the label on your own appliance beats any average. Read more in our methodology.