The answer to 'how much to replace furnace' is that the cost to replace a furnace can vary widely depending on several factors. Typically, the total cost for a furnace replacement can range from around $3,000 to $10,000 or more, including the unit, labor, and any necessary ductwork or electrical work.
The exact price will depend on the size and efficiency of the new furnace, the complexity of the installation, the cost of materials and labor in your local area, and whether you need to upgrade or replace any related components like the thermostat or ductwork. It's essential to get multiple quotes from licensed HVAC contractors in your area to get an accurate estimate for your specific home and needs.