As spring slips into summer, it's time to focus on ways of staying cool and/or making it in the shade. One of the more common methods of self-cooling is the electric fan. Fans are much cheaper than an AC unit, and they are usually portable so you can carry it with you from room to room.
Why not buy a few fans and put them in a few choice rooms? Because fans don't cool rooms, they cool people. Counterintuitive as it sounds, fans don't decrease heat, they actually increase it. The heat generated by the motor does more to heat the room than the fan does to cool it.
Fans cool humans by blowing air over our skin to increase evaporation and by "replacing stagnant air by forcing turbulence" and/or by replacing the inside air with the possibly cooler outside air. Basically, fans make us more comfortable by moving air around.
A fan going in an unoccupied room does little more than waste electricity. Therefore, if you are running fans in empty rooms to keep them cool, stop it. Turn off your fan and reduce your electricity bills.