The national average for replacing an entire HVAC system is $7,000, and costs can range from $5,000 to $10,000. This equals between $25 and $60 per square foot. The size and brand of the HVAC system, the size of the house, the length of the ductwork, and the efficiency rating of the new unit all affect prices. You can anticipate paying between $1,500 and $12,50 for new installations. Average labor costs for HVAC installations range from $500 to $2,000.