One cools with outdoor air for pennies. The other makes cold air on demand. Here is when each one wins, and how to use them together.
A whole house fan does not make cold air. It replaces warm indoor air with cooler outdoor air, so it only works when it is cooler outside than in. When it is, it costs far less: about 7 cents an hour for a CentricAir 3.4 versus about 60 cents for a 3 ton central air conditioner, at the 2026 U.S. average electricity price. Air conditioning accounted for about 19 percent of U.S. home electricity use in 2020, according to EIA. Most homes do best using the fan on cool evenings and AC on hot afternoons.
Whole house fans and air conditioners both cool a house, but they work in opposite ways. An air conditioner closes the house up and removes heat and moisture from the air inside. A whole house fan opens the house up and swaps the warm air for cooler air from outside. That difference decides when each one makes sense.
How is a whole house fan different from air conditioning?
A whole house fan moves air. An air conditioner changes it.
| Whole house fan | Central air conditioning | |
|---|---|---|
| How it cools | Replaces indoor air with cooler outdoor air | Removes heat from indoor air |
| Works when | It is cooler outside than inside | Any time |
| Windows | Open | Closed |
| Humidity | Brings in outdoor humidity | Removes moisture as it cools |
| Power draw | 143 to 749 W (CentricAir models) | About 3,270 W for a 3 ton, EER 11 unit |
| Cost per hour at 18.2¢/kWh | About 3¢ to 14¢ | About 60¢ (3 ton) |
| Fresh air | Yes, brings outdoor air through the house | Recirculates indoor air |
Fan wattage from CentricAir product pages, September 2026. AC draw calculated as 36,000 BTU per hour divided by an EER of 11. Price is EIA’s projected 2026 U.S. average residential rate.
How much cheaper is a whole house fan to run?
Roughly 8 to 10 times cheaper per hour than a 3 ton central air conditioner, for a midsize CentricAir fan.
Cost per hour at 18.2¢/kWh, EIA’s projected 2026 U.S. average. AC figures assume an EER of 11. Older or less efficient systems cost more.
The Department of Energy’s Energy Saver guidance puts it simply: ventilation is the least expensive and most energy efficient way to cool buildings. Our savings guide walks through a full summer of evenings, with the math shown.
Comfort Cool says a whole house fan can save up to 50 to 90 percent* on cooling costs, depending on your climate, your home and how many AC hours the fan replaces.
*Comfort Cool estimate, not a guarantee. Your savings will vary.
Can a whole house fan replace your AC?
In the right climate it can replace most of your evening and overnight AC, but rarely all of it.
The Department of Energy’s Building America program says whole house fans work best where summer nights cool down to about 67°F or below, and it rates dry western climates as an especially good fit. In those places, a fan can carry the house from sunset to midmorning. On the hottest afternoons, or on warm and humid nights, the air outside is not cool enough to help, and that is when AC earns its keep.
What about humidity?
A whole house fan brings in outdoor air as it is, moisture included.
An air conditioner dries the air as it cools it. A whole house fan cannot. On dry nights that does not matter, and many homeowners like the fresh air. On muggy nights the house can feel clammy even when the temperature drops, which is why whole house fans are less useful in humid climates.
How do you use a whole house fan and AC together?
Take turns. Never run them at the same time.
- Afternoon:Windows closed, AC on if you need it.
- Evening crossover:Once it is cooler outside than inside, turn the AC off and open windows.
- Night:Run the whole house fan, ideally on a timer.
- Morning:Turn the fan off and close the windows before it warms up, to hold the cool air in.
A timer or temperature control makes the handoff easy. See our guide to the best time to run a whole house fan for more on timing.
Can you set your AC to bring in outside air?
Usually not. Most home central air systems recirculate the air already inside.
The fan setting on a thermostat moves indoor air through the ducts without cooling it, but it does not pull in outdoor air unless your system was built with a fresh air intake. If you want to flush the house with cool evening air, that is the job a whole house fan is built for.
Find the CentricAir whole house fan sized for your home.
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Frequently asked questions
Can a whole house fan replace air conditioning?
In climates with cool, dry summer nights, it can cover most evenings, nights and early mornings. Most homes still need AC on the hottest afternoons and on warm or humid nights.
Is a whole house fan cheaper than AC?
Much cheaper per hour. At the 2026 U.S. average electricity price, a CentricAir 3.4 costs about 7 cents an hour, compared with about 60 cents for a 3 ton central air conditioner while its compressor runs.
Can I run a whole house fan and AC at the same time?
No. The whole house fan would push the cooled air into the attic. Use the fan when it is cooler outside, then close the windows and switch to AC when it is not.
Does a whole house fan remove humidity?
No. It brings in outdoor air as it is. On humid nights it brings humidity in with it. An air conditioner removes moisture as it cools.
Can I set my AC to pull in outside air?
Most home central air systems recirculate the air already inside. The thermostat’s fan setting moves air through the ducts without cooling it, but does not bring in outdoor air unless the system has a fresh air intake.
Keep reading
Sources
- U.S. Energy Information Administration, How much electricity is used for air conditioning in the United States?, updated March 15, 2024.
- U.S. Energy Information Administration, Short-Term Energy Outlook: Electricity, released Sept. 9, 2026.
- U.S. Department of Energy, Building America Solution Center (PNNL), Whole-House Fans, updated Sept. 29, 2022.
- U.S. Department of Energy, Energy Saver, Ventilation Systems for Cooling, accessed Sept. 2026.
- CentricAir product specifications and prices, centricair.com, accessed Sept. 2026.