The average cost to replace an HVAC system is $3,250 to $12,586, which would include installation of both a new central AC unit and gas furnace combo. If you need to replace ductwork as well, you can expect an additional $1,875 for a single story 2,200 sq. ft home. HVAC Unit Costs Most homeowners who are looking at replacing an … Continue reading How Much Does HVAC Replacement Cost?