The FAN selection key has two or three positions: Auto and On and sometimes Circ (Circulate). The On position will turn the fan on to run continuously, regardless whether heating or cooling system is turned on by the thermostat or not.
So, how much does it cost to run a small fan at night?
At the midpoint, 70 watts, if a kilowatt costs 10 cents per hour, the fan would cost 0.7 cents per hour (0.07 kwh x 10 cents). Extend that out to a month and it works out to $5.04 per month if it runs around the clock (0.7 cents per hour x 24 hours x 30 days). Two fans would be just over $10 per month.
How does a whole house fan work?
A whole-house fan is usually installed on the attic floor near the center of your house. In the late evening or early morning, the fan is turned on to exhaust hot air from the house. Cooler outdoor air enters through open windows, lowering the indoor temperature.