How much a central air conditioner should cost. Average costs and comments from CostHelper’s team of professional journalists and community of users. Adding central air conditioning to an existing forced air heating system in a , square foot house averages $, $,, and can be done by two technicians in days, with li.e or no change to the existing ducting if ducts must be added .Spending your summers sweating the heat because your existing air conditioning isn’t doing the job? You should consider replacing your old existing central air conditioning with a new energy and cost efficient unit. If you’ve lived in central Ohio for any length of time, you know that air conditioning isn’t a luxury, but an absolute necessity during the summer heat..Average cost to install central air conditioning is about $, central A C cool only for , sq.ft. upgraded . Find here de.ed information about central air conditioning costs..How Much Does Air Conditioning Cost? Most homeowners report spending between $, and $, to have air conditioning installed. This price is more typical of a central A C unit installation rather than a window central air conditioner addition which typi.y averages about $. Your total cost .