Ceiling fans can save energy and money for heating and cooling. A quick rule of thumb for sizing them matches the diameter of the fan with the largest dimension of a room. For 12 ft. or less, use a 36-in. fan. For 12 to 16 ft., use a 48-in. fan. For 16 to 18 ft., use a 52-in. fan. And for dimensions larger than 18 ft., install two fans. Placement of a ceiling fan for adequate air circulation is 7 ft. above the floor with the blades 8 to 10 inches from the ceiling. And to move more air at low speed, a fan with five blades is best.
Regarding energy savings, research has proven that ceiling fans can save energy during the cooling season by creating a gentle breeze. You get your savings then by raising your thermostat by a minimum of 2 degrees. This decreases air conditioning energy used by 10 to 15 percent, or 5 to 8 percent per degree. By reversing your fan (so it runs clockwise) during winter, you pull heat from the ceiling and push it down to the floor for more even heat.
40 Things You Should Know About a Home by Age 40, Source:https://www.rd.com/home/improvement/things-you-should-know-about-a-home-by-age-40/