HVAC
How to Estimate a Furnace Replacement
Contractor method for estimating furnace replacement: type, size, ductwork and removal.
Furnace estimates fail on the ductwork and the old-unit removal. The furnace is a quoted price; the duct modifications and the disposal are where the bid balloons.
THE SHORT ANSWER
How do you estimate a furnace replacement?
Confirm the type (condensing $6.5k, high-efficiency $5k, standard $3.5k) and size, inspect ductwork ($2k-$3.5k if reworked), then price removal, labor and permits. A typical install runs $3,500-$8,000.
Confirm the type and size
High-efficiency furnaces (90%+) run ~$5,000, condensing (96%+) ~$6,500, standard ~$3,500. Size by heat load (60-80k BTU, 80-100k, 100k+) and confirm the existing unit's rating.
Check the ductwork
If the new furnace's output or dimensions differ, expect duct modifications — $2,000-$3,500 for a partial rework. Note the filter location and return air runs on the walkthrough.
Price removal and disposal
Removing the old furnace runs $400-$600 including disposal. A permit runs $350-$500. Use the Furnace Replacement Cost Calculator to build the full quote.
Check the total
Your total should land within 10% of the calculator output before markup. Note utility rebates for high-efficiency units.