Green Mountain Boilers offers one of the broadest residential lineups in the industry, covering gas hot water, gas steam, oil hot water, and 95% AFUE condensing models. Their cast iron boilers are built for rugged Northeast conditions, and the GMHB condensing line competes with premium brands at a lower price point. We install the full Green Mountain range across Nassau and Suffolk County.
Green Mountain Boilers is a brand that Long Island contractors know well. Their tagline is "as rugged as the outdoors," and the product lineup reflects that philosophy. Every cast iron heat exchanger is water and pressure tested at the factory before assembly, and the boilers are designed specifically for cold-climate applications where reliability matters most.
What distinguishes Green Mountain from competitors like Williamson or New Yorker is the sheer breadth of the lineup. The GMGW-K series covers gas hot water from 59 to 235 MBH in seven sizes. The GMPVB power vent series handles homes where chimney venting is not ideal. The GMGS series covers gas steam. The GMOW and GMOWT handle oil applications with and without tankless coils. And the GMHB and GMCB condensing models bring 95% AFUE efficiency for homeowners who want to maximize fuel savings.
Green Mountain cast iron models feature digital operating controls with diagnostics, electronic ignition with motorized vent dampers, and removable burner trays for easy servicing. The GMGW-K models offer left or right side hydronic piping and electrical wiring options, which gives our installers flexibility in tight Long Island basements. Schedule a free estimate and we can walk you through the full lineup at your home.
Cast iron atmospheric boiler in 7 sizes from 59 to 235 MBH. 84% AFUE. Electronic ignition. Motorized vent damper. Digital control with diagnostics. Vertical vent.
Cast iron gas boiler with chimney or sidewall venting. 84% AFUE. Sizes from 42 to 225 MBH. No dependence on the chimney for draft. Great for retrofit installs.
95% AFUE wall-hung condensing boiler. GMHB for heat only (125-379 MBH). GMCB combi for heat plus hot water (150-200 MBH). ENERGY STAR certified. Direct vent.
Cast iron gas steam boiler in 7 sizes from 75 to 299 MBH. 82% AFUE. Built-in draft diverter for low-profile installations. Stainless steel burners.
Cast iron oil hot water boiler from 119 to 259 MBH at 86% AFUE. GMOWT adds a tankless coil for domestic hot water. Four sizes cover most Long Island homes.
Green Mountain cast iron boiler installations on Long Island typically range from $7,500 to $10,500 for gas and oil models. The GMHB and GMCB condensing models run higher, typically $9,500 to $12,500 installed, due to the advanced condensing technology and wall-mount installation requirements.
One of the advantages of Green Mountain is competitive equipment pricing. Their cast iron boilers are priced comparably to Williamson and New Yorker, while the GMHB condensing model is a cost-effective alternative to premium brands like Navien or Bosch while still delivering the same 95% AFUE efficiency.
GMHB and GMCB models qualify for National Grid rebates and federal tax credits thanks to ENERGY STAR certification. We also offer flexible financing through Wisetack. For a full comparison by system type, visit our cost guide.
If your home has an older Green Mountain cast iron boiler, the good news is that the current lineup is a natural fit for a direct replacement. The GMGW-K series has similar footprints and piping connections to earlier Green Mountain gas models, which simplifies installation and keeps the project cost down.
For homeowners looking to make a bigger efficiency jump, the GMHB condensing boiler is a significant upgrade from any cast iron unit. Going from 82-84% AFUE to 95% AFUE means roughly 12-15% less fuel consumption per heating season. The GMCB combi version also eliminates the need for a separate water heater, which saves both space and money.
If you have a Green Mountain oil boiler and gas is now available on your street, replacement time is a natural point for an oil to gas conversion. We can compare the cost of a new GMOW oil unit versus converting to a gas model from Green Mountain, Navien, Weil-McLain, or another brand during your free in-home estimate.
From your first call to your first warm morning, here is what to expect when you replace your boiler with a Green Mountain.
We evaluate your current system, calculate your heating load, and recommend the right Green Mountain model. We review all rebates and financing options before you decide.
Once approved, we schedule at your convenience. We stock popular Green Mountain models for fast turnaround. Emergency service is available during the heating season.
Our crew removes the old boiler, installs the new Green Mountain, connects all piping and venting, and tests the system. Most residential installations are completed in one day.
We register your warranty, submit rebate paperwork, and provide documentation for any applicable tax credits. We are here for any questions after the job.
The complete Green Mountain residential boiler lineup we install on Long Island. Condensing, cast iron gas, and cast iron oil models available.
| Model | Type | AFUE | Sizes | Application |
|---|---|---|---|---|
| GMHB Series | Condensing | 95% | 125, 160, 227, 379 MBH | Wall-hung condensing gas heating boiler. Direct vent. Natural gas or propane. ENERGY STAR certified. Digital display with diagnostics. Anti-wind and flame stabilization controls. 10-year heat exchanger warranty. |
| GMCB Series | Condensing Combi | 95% | 150, 200 MBH | Wall-hung condensing gas combi boiler. Provides space heating and domestic hot water. Eliminates the need for a separate water heater. Direct vent. ENERGY STAR certified. |
| Model | Type | AFUE | Sizes (MBH) | Application |
|---|---|---|---|---|
| GMGW-K Series | Atmospheric | 84% | 59, 92, 120, 149, 175, 205, 235 | Gas hot water atmospheric boiler. 7 sizes. Cast iron with dry leg end sections. Digital control with diagnostics. Electronic ignition. Motorized vent damper. Removable burner tray. Vertical vent. |
| GMGW-D Series | Atmospheric | 84% | 262, 299 | Larger capacity gas hot water atmospheric boiler. 2 sizes for bigger homes. Electronic ignition. Motorized vent damper. Chimney or sidewall venting. |
| GMPVB Series | Power Vent | 84% | 42, 75, 112, 150, 187, 225 | Power vented gas hot water boiler. 6 sizes. Chimney or sidewall venting for maximum installation flexibility. Cast iron. No chimney dependence for draft. |
| GMGS Series | Steam | 82% | 75, 112, 150, 187, 225, 262, 299 | Gas steam atmospheric boiler. 7 sizes. Built-in draft diverter for low-profile installations. Stainless steel burners. Electronic ignition. Chimney vented. |
| Model | Type | AFUE | Sizes (MBH) | Application |
|---|---|---|---|---|
| GMOW Series | Hot Water | 86% | 119, 175, 224, 259 | Oil-fired hot water boiler. Cast iron construction. Chimney vented. Burner sold separately. 4 sizes cover most residential applications. |
| GMOWT Series | Hot Water + Tankless | 86% | 119, 175, 224, 259 | Same as GMOW with integrated tankless coil for domestic hot water. Eliminates the need for a separate water heater in homes with limited space. |
Long Island homeowners share their experience with Green Mountain boiler installations by our team.
"We needed to replace a 22-year-old gas boiler and our contractor recommended the Green Mountain GMGW-K. The price was lower than what we were quoted for comparable brands, and the installation went smoothly. The digital control is a nice upgrade from the old thermostat setup. Heating evenly and the gas bill is about 10% lower."
"Our chimney liner failed and relining it was going to cost thousands. Domino's suggested a GMPVB power vent model instead, which vents through the sidewall. It saved us the entire chimney expense and actually performs better than the old boiler. Clean install, everything done in a day."
"We went with the GMHB condensing boiler when we converted from oil to gas. The savings compared to our old oil boiler have been substantial. Domino's handled the gas line, removed the oil tank, and installed the new boiler all in the same project. The rebate from National Grid covered a nice chunk of the cost."
We install and service Green Mountain boilers across every town in Nassau County and Suffolk County. Based in Melville for fast response.
Every town from the Queens border to the Suffolk line. Garden City, Levittown, Massapequa, Hempstead, and 60+ more communities.
Nassau County DetailsOur home base. Huntington to Montauk, including the North Fork, South Fork, and everything in between.
Suffolk County DetailsCommon questions Long Island homeowners ask about Green Mountain boiler replacement and installation.
Get a free in-home estimate. We will evaluate your current system, recommend the right Green Mountain model for your home, and provide a complete quote with all available rebates factored in.