The cost to install a window air conditioner averages between $ and $, depending on the size you need. Installing a window air conditioning unit can bring added comfort for a reasonable price, but it will be less powerful than a central air conditioning system. If you have a bigger home with multiple rooms, you will probably need to have .Average cost to install central air conditioning is about $ sq.ft. home . Find here de.ed information about central air conditioning installation costs..Central Air Installation Prices. Window air conditioners are certainly better than no air conditioners at all on a summer day, but quieter, more efficient central air conditioning represents a major step up in household comfort..But adding central air is easier and less costly than you might think. When added to an existing forced air heating system, central air for a , square foot home costs $, to $, and can be done by two technicians in two to three days, often with li.e or no change to the ducting..