How Much Does Gas Boiler Installation Cost on Long Island in 2026?

If your Long Island gas boiler is more than 15 years old, starts cycling more than it heats, or you got a four-figure repair quote, you are probably weighing the same question every Nassau and Suffolk County homeowner ends up asking: how much is a new gas boiler actually going to cost in 2026, and is now the right time to replace it?

This guide gives you the honest cost ranges for Long Island in 2026, walks through what actually drives the price up or down on your specific install, and explains the permit and inspection rules in Nassau and Suffolk County so you do not get caught later.

Gas boiler installation cost on Long Island in 2026 — the real ranges

Here is what a homeowner in Nassau or Suffolk County should expect to pay for a full gas boiler installation in 2026, including the boiler itself, all labor, near-boiler piping, gas connections, permits, and the post-install inspection.

Standard-efficiency cast-iron boiler ($5,500 – $8,500 installed)

This is the most common replacement on Long Island — an 80 to 84 percent AFUE atmospheric-vent cast-iron boiler, typically replacing a similar-vintage cast-iron unit. Brands like Burnham, Weil-McLain, and Crown dominate this category. It is the cheapest option upfront and the longest-lasting (often 25 to 30 years), but it is also the least efficient.

High-efficiency condensing boiler ($8,500 – $14,000 installed)

A 92 to 95 percent AFUE condensing boiler — Navien, Lochinvar, Viessmann, or similar — costs more upfront but cuts your annual heating bill by 10 to 15 percent compared to standard-efficiency. It vents through PVC out the side wall instead of up a chimney, which means no chimney liner work is needed. We are Navien-certified and this is the most common upgrade we install today.

Combi boiler with on-demand hot water ($9,500 – $15,500 installed)

A combi boiler heats your home and provides domestic hot water on demand — no separate water heater required. This is a great option if you are short on basement space or your water heater is also at end of life. The catch: combi units are sized to the larger of your heating load or your hot water demand, so very large homes sometimes need a separate setup.

Steam boiler replacement ($7,500 – $12,500 installed)

If you have old cast-iron radiators with one pipe going to each, you have a steam system — common in older Long Island homes. Steam boiler replacement is a specialty: piping must be sized correctly, the Hartford loop has to be rebuilt to code, and pitch on returns matters more than people think. Cheapest is not the right answer here.

What changes the price on your specific install

The ranges above span $3,000 to $6,000 because real-world installs vary. Here is what actually moves the number up or down.

Chimney liner work ($800 – $2,200 extra)

If you are replacing an atmospheric boiler in an old masonry chimney, code in both Nassau and Suffolk County usually requires you to install a stainless steel liner sized for the new appliance. If you have already disconnected a water heater to a separate vent, you may need to resize the liner. Condensing boilers vent out the side wall and skip the chimney entirely — that is part of why they cost less than the AFUE difference alone would suggest.

Near-boiler piping rebuild ($600 – $1,500 extra)

If the piping near the old boiler is corroded, undersized, or installed wrong (we see this a lot on 1970s-1980s homes), it needs to be rebuilt to match the new boiler. Some homes need a low-loss header or hydraulic separator added for a condensing install. This is invisible to you but matters a lot to whether the new boiler hits its rated efficiency.

Zone valves and circulators ($300 – $800 each)

If your zone valves or circulators are also at end of life, doing them at the same time saves a return service call. We always quote them out separately so you can decide.

Indirect water heater ($1,800 – $3,200 extra)

If you have a tank water heater that is also old, pairing the new boiler with an indirect water heater (which uses the boiler to heat domestic water) gives you essentially unlimited hot water and a 10 to 15 year tank life, vs the 8 to 12 year life of a standalone gas water heater.

Permit fees and inspection ($175 – $450 in Nassau, $200 – $500 in Suffolk)

Both counties charge plumbing and gas permit fees that vary by town. We pull the permits on your behalf and the cost goes on the invoice — never trust an installer who tries to skip permits to save you money. See the permit FAQ at the bottom of this guide.

When repair makes more sense than replacement

Not every old boiler needs to be replaced today. A general rule we use:

• Repair if the boiler is under 12 years old, the repair is under $500, and you have not had a service call in the last 18 months.
• Get a second opinion if the repair is $500 to $1,500 and the boiler is 12 to 18 years old.
• Replace if the boiler is over 20 years old, repair quotes are over $1,500, or you are getting more than one service call a year.

We do free in-home evaluations for Long Island homeowners. We will tell you straight up whether your boiler is worth fixing — we have no incentive to push you into a $9k install if a $300 repair gets you another five winters.

What to expect on install day

A typical condensing boiler replacement in a Long Island home goes like this:

1. Morning: We arrive, lay protective floor covering from the door to the boiler room, shut down the old boiler, drain it, and remove it.
2. Midday: New boiler set in place, gas line connected, vent run, near-boiler piping built, condensate drain run.
3. Afternoon: System filled and bled, electrical and thermostat wiring, commissioning (combustion analysis, gas pressure check, safety verification), heat tested on every zone.
4. End of day: Walk-through with you on how the new system works, paperwork left for permit inspection, scheduled with the town for the next available inspector visit.

You have heat back on the same day. The permit inspection happens later (usually 1 to 4 weeks out depending on town schedule) and we handle that.

What you should never see on a quote

A few things that should be red flags when you compare estimates from Long Island contractors:

• No permit listed in the line items, or "permit pulled by homeowner" — that is the contractor trying to skip the inspection
• No mention of post-install combustion analysis or commissioning
• A model number you cannot find in a manufacturer warranty database
• Significantly below-market price ($4,500 for a condensing install would suggest used equipment or no permit)
• Promises of "deep" rebates with no specific National Grid or PSEG program named
• Pressure to sign today for a discount

A legitimate Long Island plumber gives you a written quote, lets you take it home, and is there when you call back with questions.

The Long Island plumber checklist

Whoever you hire — us or someone else — make sure they can answer yes to all of these:

• Licensed plumber, license number on the quote and on the invoice
• General liability insurance, $1M minimum, certificate emailed to you on request
• Pulls plumbing and gas permits in your specific town
• Does combustion analysis on every install
• Manufacturer-trained for the brand they are installing (Navien-certified, Lochinvar-trained, etc.)
• Provides a written one-year labor warranty on top of the manufacturer warranty

If they get hesitant on any of those, get another quote.

Frequently asked questions

How long does a gas boiler installation take on Long Island?

A straightforward boiler swap (same fuel, same location, no chimney liner work) typically takes one full day. Add half a day to a day for chimney liner replacement, baseboard or radiator changes, or near-boiler piping that needs to be rebuilt.

Do I need a permit to replace a gas boiler in Nassau or Suffolk County?

Yes. Both Nassau and Suffolk County require a plumbing permit and a gas permit (or combined permit, depending on town) for boiler replacement. Reputable installers pull the permit on your behalf and schedule the post-install inspection — never accept a no-permit job, because it voids your homeowners insurance if the boiler ever causes damage.

Is a high-efficiency condensing boiler worth the extra cost?

For most Long Island homes, yes — over the boiler's 15 to 20 year life, the fuel savings from going from an 80 percent AFUE atmospheric boiler to a 95 percent AFUE condensing model typically pays back the extra $2k to $4k upfront within five to eight years. The exception is small, well-insulated homes with low heating loads where the absolute dollar savings is small.

How long does a gas boiler last?

Cast-iron gas boilers commonly last 25 to 30 years when maintained. Modern high-efficiency condensing boilers usually last 15 to 20 years. Once a boiler hits the upper end of its life and starts needing repairs over $500, replacement is usually the better call.

Can you install a new boiler in the same day you remove the old one?

Yes — that is the standard. We arrive in the morning, drain and remove the old boiler, install the new one, run the gas and water connections, and have heat back on by end of day. We only leave a home without heat overnight if a permit inspection forces a delay.