Cost

• Because of the necessity for additional equipment like duct work and air handlers, central air units typically cost considerably more than window air conditioners. Central air systems often cool an entire house, though, and may cost less than placing a window unit in each room.
  
  

Efficiency

• Although both window and central air conditioners offer a number of energy-saving options according to the air conditioning website HVAC Key, central units efficiently evacuate hot air and recirculate cold air to achieve higher efficiency. An air conditioning technician must properly size a central unit to a home, though, as a central system that is too large or too small will not offer maximum efficiency.
  
  

Considerations

• A number of factors affect the operation and efficiency of both central and window air conditioners. These factors include the home's insulation and the regional climate, and such localized factors like humidity can influence the choice between a central or window air conditioner.