Window fans use little energy and can provide effective cooling in many climates. Window fans are best used in windows facing away from the prevailing wind and exhausting hot air from your home. To cool as much of your home as possible, tightly close windows near the fan and open windows in rooms far from the fan, preferably on the windward side of your home. Windows near cooler, shaded outdoor areas provide the best intake air.
In multi-level houses, the fan should be located on the upper level, if possible, and the open windows should be located on a lower level. If that's not practical, you may want to independently ventilate each level of your home with separate fans.
Depending on the layout of your home, you might want to use several window fans working together to pull the air through your home. For instance, fans in several upstairs bedrooms will assure that each bedroom is cooled, and will work together to pull air in through the rest of your home.