The energy cost of ceiling fans, on the other hand, is much different. Whereas a 2.5-ton central air conditioner uses about 3,500 watts and a window A/C unit typically uses between 500 to 1,500 watts, a ceiling fan uses only 15 to 95 watts depending on its size and speed.ooking at those New York Times statistics that compared the cost of ceiling fans versus air conditioning a little further, we can do the math on the monthly costs: • A central A/C unit would cost about $129.60 per month. • A window A/C unit would cost about $50.40 per month.