The cost to replace an HVAC system varies based on factors like the size of the home, the type of system, and local labor rates. On average, a complete HVAC system replacement may range from $5,000 to $10,000 or more. High-efficiency systems and additional features can increase costs. It's advisable to obtain multiple quotes from reputable HVAC contractors, considering factors like energy efficiency and warranty, to make an informed decision based on your specific needs and budget.