HVAC
How to Estimate a Boiler Replacement
Contractor method for estimating boiler replacement: type, size, valves and the hidden line items.
Boiler bids fail on the zone valves and the old-unit removal. The boiler is a known price; the valves, the flushing and the permit are where the quote grows.
THE SHORT ANSWER
How do you estimate a boiler replacement?
Confirm the type (condensing $8.5k, high-efficiency $6.5k, standard $4.5k) and size, count the zone valves ($300 each), then price removal, flushing, labor and permits. A typical install runs $6,500-$12,000.
Confirm the type and size
Condensing boilers (95%+) are the modern standard and run ~$8,500; high efficiency ~$6,500; standard ~$4,500. Size is by heat load — 60-80k BTU, 80-100k, or 100k+. Confirm the existing unit's rating before quoting.
- Note the current boiler rating
- Check the heat distribution system
- Confirm gas line size
- Check the chimney or venting option
Count the zone valves
Zone valves control each heating zone and run ~$300 each. A 2-zone house is the common baseline; a 4-zone house adds real money. Count them on the walkthrough, never from the listing.
Price the hidden work
Removing and hauling the old boiler runs $500-$800. Power-flushing the system adds ~$300-$500. Permits run $400-$600. Use the Boiler Replacement Cost Calculator to build the full quote.
Check the total
Your installed total should land within 10% of the calculator output before markup. Then note the efficiency rebates available in your state — they change what the homeowner pays.