How an Air Conditioner Works

• All air conditioners work on the same basic principles. The unit pulls in air from inside the home and blows it across cold copper coils filled with refrigerant gas. This gas absorbs the heat from the air, and the coils "sweat" from the temperature differential. The sweat forming on the coils is humidity removed from the air inside the home. This sweat, or condensation, drips down in to a condensate pan and is drained outside. The refrigerant gas that has absorbed the heat from the air is pumped outside the home, where it disperses the heat before returning inside to repeat the process.
  
  

Air Conditioners Dehumidify

• As a window air conditioner cools and removes humidity from the air, it is functioning as a dehumidifier in addition to reducing the air temperature. Humidity can make it feel warmer than it is, so reducing the indoor humidity increases the comfort level. Air conditioners dehumidify only the air that is inside the house, so a rainy day should not cause more work for an air conditioner in a well-insulated home.
  
  

Increased Humidity

• Many homes are not sufficiently insulated. Because of this, a window air conditioner may remove more humidity from the inside air and drain more condensate outside during a rainy day. Most window air conditioners do not have a setting to turn on at a specific humidity level, however, and rely solely on indoor temperature to regulate their cycling. A window air conditioner typically does not run longer because of the increased indoor humidity.
  
  

Increased Cooling

• The side of the air conditioner coils that disperses the heat does not rely on evaporation for cooling, like the human body does. So the increased humidity does not increase the amount of time it takes the unit to disperse heat. Rainwater running across the coils on the hot side of the air conditioner may actually take with it some heat, improving the effectiveness and efficiency of the air conditioner. For this reason, a homeowner running an air conditioner in the rain may actually feel as though it is cooler in the home than is usual.