Ceiling fans move air much more efficiently and with less noise than smaller portable fans. And they consume a small fraction of the power of air conditioners: often less than 100 watts, that is, 1/100 or less than central air conditioners.
Ceiling fans and air conditioners cool by distinctly different methods. Air conditioners cool the air; ceiling fans do not cool the air: they provide evaporative cooling; in other words: ceiling fans cool people by moving air and by evaporating moisture from their skin.
But they can work in conjunction. Each one degree increase (Fº) in your air conditioner thermostat setting can decrease your air conditioner bills by, say, 5%. And ceiling fans make that possible. Just turn your ceiling fan and raise the AC setting by 4ºF/3ºC or slightly more. You will not notice any loss of comfort.
You may use your air conditioner in conjunction with ceiling fans (or other circulating fans) to get energy savings.
See, for details on ceilings:
Ceiling Fans Can Work in Conjunction with Air Conditioners.
A high quality ceiling fan is several times more effective than small circulating fans. They move much more air and are in a class of their own.
But small portable fans, with a reasonable capacity and properly positioned, can also be very useful and provide significant energy improvements.
See: Portable Fans Efficiency.
It’s often said that ceiling fans are useful during the winter, to move the heat away from the ceiling toward the inhabited parts of rooms, providing more comfort and energy savings. But such strategy is only truly effective in high ceiling rooms (12 feet of more).
Window-fans are ventilating fans. They are intended to bring outside fresh air into the house, drawing the inside hotter air out of it, through the windows...
That’s different from ceiling fans, designed to move inside air and to cool the people in their 'line of sight'.
To know how to use window-fans in your cooling strategies, see: Window Fans Strategies for Home Energy Improvements.
Air conditioners can cost thousands of dollars to install and to run. But not whole-house fans.
They are a low-cost cooling method. If you live in a hot climate with cool evenings, they are an option to consider.
Attic fans - either electric or solar - are popular, but typically ineffective and in some cases counterproductive. They may consume more energy than they save. There are better ways of dealing with overheated attics.
Spot kitchen and bathroom fans are an important piece of exhaust ventilation, in most homes. But airtight houses may need more than just spot exhaust ventilation.
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