How much does a new gas boiler cost?

Prices checked October 2026. Wages: BLS, May 2025.

Condensing boilers cost more to buy and, on average, less to put in. That pattern comes from the Department of Energy's 2023 proposed boiler rule, and it shapes the estimate above. Condensing units are smaller, hang on a wall and vent through plastic pipe. Standard boilers are heavy and vent into a chimney that may need work. Keep in mind these figures come from a proposed-rule analysis rather than a final rule. Steam boilers are not covered, and a flue liner and a condensate pump appear below as separate extras.

Three kinds of gas hot-water boiler are priced: a standard non-condensing boiler (typically cast iron), a condensing boiler, and a combi that heats the house and makes domestic hot water. Equipment prices come from public retailer listings in the 75,000 to 125,000 BTU range common in houses. Installation is DOE's average, inflated to today's dollars. Half of it counts as labor and is scaled to plumber and pipefitter wages in your area, since plumbing and heating contractors put in a lot of boilers.

Installed price by size, national

Installation averages $4,415 nationally for the common size (DOE, inflated to August 2026); about 50% of that is labor, which we scale to local wages.

Extras that may be added

What moves the price

Standard, condensing or combi

Efficiency runs from about 84% AFUE for a baseline gas hot-water boiler to 95% and up for condensing models with modulating burners. ENERGY STAR's gas boiler label starts at 90%. Condensing boilers cost more to buy. A combi replaces both the boiler and a separate water heater, which frees up floor space and retires a second appliance.

Chimney and venting

Replacing a standard boiler often means checking an old masonry chimney. If a condensing boiler moves the exhaust out the wall, a water heater left in the chimney may need a liner. DOE's furnace analysis found flue updates, including relining, in a share of replacements, and the same issue applies to boilers.

Near-boiler piping and controls

Many installs re-pipe the area around the boiler: circulator pumps, zone valves, an expansion tank for the heating loop, air separation and a low-water cutoff where required. Condensing boilers work best with lower return-water temperatures and often come with outdoor reset controls. The amount of re-piping varies widely and is a big reason boiler bids spread apart.

Weight and access

A cast iron boiler in a tight basement takes more people and more hours to remove and set than a wall-hung unit. Expect to pay for the stairs. Narrow doors and old asbestos-wrapped piping (which needs a licensed abatement contractor) add to the job too.

Local trade wages

The labor half of DOE's average is adjusted to the 25th, median and 75th percentile plumber and pipefitter wage for your metro or state, from the May 2025 federal wage survey.

Repair or replace?

Boilers are the longest-lived system on this site. DOE's proposed-rule analysis puts the average gas hot-water boiler at about 27 years, and some inspection charts go as high as 40. So circulators, igniters, controls, relief valves and expansion tanks count as routine repairs, and fixing them almost always makes sense. Replace when the heat exchanger or cast iron sections leak, or when a boiler near the end of DOE's range needs a major part. A condensing upgrade can also justify it if the efficiency gain in your climate pays back over the years you plan to stay. Ask for a heat-loss calculation. Old boilers are often far bigger than the house needs.

Run the numbers for your unit.

What a complete quote lists

• Boiler model, input BTU and AFUE, and whether it is standard, condensing or combi
• Heat-loss calculation or the basis for sizing
• Removal of the old boiler, including any abatement handled by a licensed contractor
• Venting: chimney liner, sidewall PVC or stainless vent, and combustion air
• Near-boiler piping, circulator pumps, zone valves and air separator
• Expansion tank, relief valve, fill valve and backflow preventer on the heating loop
• Condensate neutralizer and drain or pump for condensing models
• Controls: thermostat wiring and outdoor reset sensor
• Gas connection, permit and inspection
• Heat exchanger warranty, parts warranty and labor warranty

Paste your quote and we'll tick these off for you.