When it comes to what were originally patented as "electric air agitators", we are, um, fans. Whenever we do a list of ways to live without air conditioning, ceiling fans are near the top. Yet building expert Carl Seville, AKA the Green Curmudgeon, calls them evil, and he as a point. He writes below the catchy title "Ceiling Fans are Evil" at Green Building Advisor:
I am surprised at how few people understand the basic concept of fans — that they make you feel cool due to the movement of air across your skin. The same way a breeze cools you off, a ceiling fan can make you feel cooler, but only if you are close enough to it to feel the air blowing on you. If you can’t feel it, it isn’t doing any good.
The trouble is, people often leave them on when they leave the room, thinking that they actually are doing some cooling, when in fact every electric motor generates some heat, so they are actually heating the room by running.Carl suggests that you choose your fan carefully, buy the one that delivers the most CFM per watt, (spreadsheet is available from Energy Star and the gorgeous Haiku fan comes out on top)
Most importantly, turn the thing off when you leave the room. More at Green Building Advisor.