Central Air Conditioners
Central air conditioners circulate cool air through a system of supply and return ducts. Supply ducts and registers (i.e., openings in the walls, floors, or ceilings covered by grills) carry cooled air from the air conditioner to the home. This cooled air becomes warmer as it circulates through the home; then it flows back to the central air conditioner through return ducts and registers.
Ductless mini-split air conditioners and heat pumps work the in the same way as central air conditioners, the difference being the lack of ducts. The systems work by transferring differences in temperature between the inside and outside of a home. The main advantages of mini split air conditioners and heat pumps are their small size and flexibility for zoning or heating and cooling individual rooms.
Room Air Conditioners
Room air conditioners, sometimes referred to as window air conditioners, cool rooms rather than the entire home or business. If they provide cooling only where they’re needed, room air conditioners are less expensive to operate than central units, even though their efficiency is generally lower than that of central air conditioners.
In low-humidity areas, evaporating water into the air provides a natural and energy-efficient means of cooling. Evaporative coolers, also called “swamp” coolers, rely on this principal, cooling outdoor air by passing it over water-saturated pads, causing the water to evaporate into it. The 15°–40°F cooler air is then directed into the home, and pushes warmer air out through windows.