Central Air Average Costs. The actual cost of central air installation depends on a number of factors, including the size of the home as well as the unit’s tonnage and SEER rating. 1  In a 2,000 square foot home with existing ductwork, central air conditioning costs $3,000 to $5,000 installed.entral Air Average Costs. The actual cost of central air installation depends on a number of factors, including the size of the home as well as the unit’s tonnage and SEER rating. 1  In a 2,000 square foot home with existing ductwork, central air conditioning costs $3,000 to $5,000 installed.