Boiler replacement on Long Island. Straight answers on aging cast iron, gas boilers $6,500-$11,000 installed, free estimates.
Boiler replacement runs $6,500–$11,000 for gas, $9,000–$14,000 for a high-efficiency or combi unit, and $7,500–$13,000 for oil, installed. Replacement estimates are free. For repair pricing on your existing boiler, see our boiler repair cost guide.
A cast iron boiler at 15 years often has a decade left; at 20, the calculus tightens; at 25 and beyond, most repairs are money spent on borrowed time. The deciding factors are the condition of the sections and the pattern of repairs, not the age alone. A 20-year-old Burnham in a dry Dix Hills basement with clean water chemistry can outlast a 12-year-old boiler that has been limping along with a weeping relief valve and repeated circulator failures. When a repair quote arrives, multiply the boiler's age by the repair cost: past $5,000, the smart money goes to replacement. A $700 zone-valve-and-circulator repair on an 18-year-old boiler works out to $12,600 on that scale.
Leaking sections are the exception to every wait-and-see argument. Water inside the jacket or rust trails down the boiler face mean the heat exchanger itself is failing, and that is not economically repairable on a residential unit.
Timing the decision is easier than most homeowners assume, because boiler failures on Long Island cluster in the first true cold week of the season, exactly when every installer's schedule fills. An estimate gathered in the fall — free, written, still valid when you need it — turns a January failure into a scheduled installation instead of an emergency negotiation from a cold house.
The default upgrade pitch is a condensing boiler, and for many homes it is right: sealed combustion, no chimney dependence, and real fuel savings when the system runs low return temperatures. But baseboard systems designed around 180-degree water in Shirley's postwar housing, for example, only let a condensing boiler condense during milder weather, which trims the advertised savings. Sometimes a quality cast iron replacement at $6,500–$11,000 is the honest recommendation, and we make it. We install Weil-McLain, Burnham, Peerless, Utica and Slant/Fin cast iron equipment along with Buderus and Lochinvar condensing units, and we service all the major brands regardless of who installed them.
A 2,000 square foot house is the most common replacement we quote, and the honest sizing answer starts near 30–40 BTU per square foot but ends with a heat-loss calculation — older Locust Valley homes with original glazing routinely need more than the rule of thumb, tighter renovated ones need less.
Replacement day itself is one working day for most hot-water systems on Long Island; steam takes longer, because header piping and the boil-out are steps that do not tolerate shortcuts. Either way, you go to bed that night with heat.
Independent efficiency references such as ENERGY STAR back up what our replacement math shows: the jump from an old cast-iron unit to condensing equipment is where the fuel savings live.
| Job | Typical Long Island Price | Notes |
|---|---|---|
| Gas boiler, installed | $6,500 – $11,000 | Like-for-like cast iron replacement |
| High-efficiency or combi boiler | $9,000 – $14,000 | Condensing, direct-vent through the sidewall |
| Oil boiler, installed | $7,500 – $13,000 | Common east of the gas mains |
| Indirect water heater add-on | $2,000 – $3,500 | Best added during the boiler swap |
Ranges reflect typical Nassau and Suffolk pricing. Your exact price is quoted upfront after diagnosis. Prices as of August 2026.
Leaking sections, rusted-through jackets, repeated repairs in one season, and parts that are no longer stocked are the strong signals. Age matters but condition rules: we inspect before we recommend, and if a repair extends the boiler's life economically, that is what we propose.
Typically $6,500–$11,000 for a gas boiler or $9,000–$14,000 for a high-efficiency unit, installed. The house size sets the starting point but the heat-loss calculation and piping condition set the final number, which is why we quote only after seeing the basement.
Yes, if a gas main serves your street. That is an oil-to-gas conversion, which adds gas piping, chimney lining and tank abandonment to the boiler cost. When a main is not available, a modern oil boiler at $7,500–$13,000 installed is a strong system in its own right.
It depends on your radiation. Systems that can run cooler return water — radiant floors, generous baseboard, cast iron radiators — let a condensing boiler earn its premium. High-temperature baseboard systems see smaller gains, and we tell you which category your house falls into before you decide.
Cast iron gas boilers commonly reach 25–35 years with maintenance; condensing boilers average 15–20; oil boilers 20–30. Salt air near the shore and damp basements shorten those figures, and an annual service visit extends them.
Moving from a decades-old boiler to a properly sized modern one usually cuts fuel use meaningfully, from both the efficiency rating and the correct sizing. The exact savings depend on your radiation and fuel; we estimate it for your house during the free estimate rather than promising a universal percentage.
Heat-loss-sized boiler installs.
Cold zones, leaks and circulator failures.
Navien and other combi and tankless units.
Everything we repair, install and maintain across Long Island.
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