The thermostat decides how often your attic fan runs, and that decides how much it costs. Here is the setting we recommend and why.
Set an attic fan thermostat to about 110°F. That is the setting CentricAir’s installation manual recommends for the best energy savings. Lomanco, another attic fan maker, ships its thermostats set to turn on at 100°F and off at 85°F. Lower settings make the fan run longer, and the Department of Energy’s Building America program notes that attic fans can use more electricity than they save in air conditioning.
On a sunny summer afternoon, an attic can get far hotter than the air outside. A thermostat on an attic fan watches that temperature and turns the fan on once it passes the number you set, then off again once the attic cools. Pick too low a number and the fan runs for hours for little benefit. Pick a sensible one and it only runs when the attic is truly hot.
What is the best temperature setting for an attic fan?
110°F, according to CentricAir’s installation manual.
The CentricAir manual says to set the thermostat to 110°F for the best energy savings. That lets the fan run through the hottest part of the day without running every warm morning. If you want a second reference point, Lomanco sets its thermostats at the factory to switch on at 100°F and off at 85°F, with an adjustable range of 60°F to 120°F.
Why not set it lower?
More runtime costs more electricity, and a lower setting pulls more air through any gaps in the ceiling.
An attic fan only moves attic air, so running it when the attic is barely warm adds cost without much benefit. A lower setting also means the fan pulls more air, so any gaps in your ceiling leak more conditioned air up into the attic.
| Hours the fan runs | Energy (180 W fan) | Cost at 18.2¢/kWh |
|---|---|---|
| 1 hour | 0.18 kWh | about 3¢ |
| 8 hours a day for 30 days | 43 kWh | about $8 |
| 8 hours a day for 90 days | 130 kWh | about $24 |
Example uses the CentricAir attic fan’s 180 watt rating and EIA’s projected 2026 U.S. average residential price. Your rate is on your utility bill.
Where should the thermostat go?
Near the fan, but not in the airstream.
CentricAir’s manual says to secure the thermostat near the attic fan without placing it in the fan’s airflow. If moving air blows across the sensor, it can shut the fan off early or cycle it on and off. Mounting it a short distance away lets it read the attic’s real temperature.
Should you use a humidistat too?
Optional. It turns the fan on when attic humidity climbs, not just temperature.
Some attic fans include a humidistat or offer one as an add on. Lomanco recommends setting it to 70 to 80 percent for automatic operation, and dropping it to 20 to 40 percent only if the attic stays too humid and mold or mildew is a concern. Building America points out a tradeoff: running a fan at night can pull humid outdoor air into the attic.
How do you check that the thermostat works?
On a warm day, turn the dial below the current attic temperature and listen for the fan.
If the fan starts, the thermostat and power are working. Set the dial back to your chosen temperature. If it does not start, confirm the outlet has power before assuming the fan or thermostat has failed. Our attic fan replacement guide covers what to do next.
Can you control an attic fan without a thermostat?
Yes. Timers, switches and remotes all work.
The CentricAir gable attic fan comes with a choice of an adjustable thermostat or an on/off remote control with timer, at no extra charge. A thermostat is the most hands off. A remote suits owners who want to decide when the fan runs.
The CentricAir gable attic fan ships with an adjustable thermostat or a remote with timer.
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Frequently asked questions
What temperature should my attic fan be set at?
CentricAir recommends 110°F for the best energy savings. Lomanco, another attic fan maker, ships its thermostats set to turn on at 100°F and off at 85°F.
Should my attic fan run all the time?
No. A thermostat runs it only when the attic is hot, which keeps runtime and electricity use down.
What humidity should an attic fan humidistat be set to?
Lomanco recommends 70 to 80 percent for automatic operation, and 20 to 40 percent only if the attic stays too humid and mold or mildew is a concern.
Where should the attic fan thermostat go?
Near the fan but out of its airstream, according to CentricAir’s installation manual.
How much does it cost to run an attic fan?
The CentricAir attic fan draws 180 watts, about 3 cents an hour at EIA’s projected 2026 U.S. average electricity price of 18.2 cents per kWh.
Keep reading
Sources
- CentricAir, Attic Fan Installation Manual (PDF), uploaded March 2025, accessed Sept. 2026.
- Lomanco Support, Power vent thermostat and humidistat settings, accessed Sept. 2026.
- U.S. Department of Energy, Building America Solution Center (PNNL), Attic Ventilation Fans, updated Sept. 21, 2022.
- U.S. Energy Information Administration, Short-Term Energy Outlook: Electricity, released Sept. 9, 2026.
- CentricAir Gable Mounted Attic Fan product page, centricair.com, accessed Sept. 2026.