The answer to 'average cost for system upgrade' is that the cost can vary widely depending on several factors. Typically, a full HVAC system replacement can range from $5,000 to $15,000 or more, depending on the size of your home, the type of system, and the complexity of the installation.
Some key factors that influence the cost include the efficiency rating of the new system, the need for ductwork modifications, the accessibility of the installation site, and any necessary electrical or structural work. Additionally, the cost can vary significantly by geographic region and local labor rates.