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High efficiency, Weil-McLain quality

Whether you’re a homeowner, contractor or building engineer, there’s a Weil-McLain high-efficiency boiler that delivers the performance you need. The lineup is engineered to live up to our legendary standards and push hydronic heating forward at the same time.


"We have a long standing relationship with Weil-McLain, and we trust the quality of their boilers. The SVF boilers were the perfect match for the space."

- Eric Cameron, project manager, Nu-Mun Contracting.   Read case study

Residential boilers

Eco Tec High Efficiency Residential Boiler


This premium heat-first combination boiler provides hot water when you need it and comfort where you want it with extreme efficiency.

Evergreen Pro High Efficiency Residential Boiler


Quiet, sleek and sustainable space heating that’s adaptable to any residential heating application.

Ultra Series 4 High Efficiency Residential Boiler

Ultra Series 4

This corrosion-resistant boiler is designed to operate in low-temperature condensing applications.

GV90+ High Efficiency Residential Boiler


Our industry-leading, cast iron dependability meets high-efficiency performance with this boiler great for high-temperature systems.

AquaBalance High Efficiency Residential Boiler


We call this low-cost combination boiler the “cold-weather combi” because it efficiently serves the space and water heating of a home in even the coldest climates.

Commercial boilers

Evergreen High Efficiency Commercial Boiler


Larger Evergreen models are ideal for light-to-medium commercial and/or multi-unit residential installations.

SlimFit High Efficiency Commercial Boiler


The cast aluminum SlimFit is the fastest, easiest solutions for limited-space commercial retrofits.

SVF High Efficiency Commercial Boiler


This state-of-the-art boiler is ideal for schools and municipal buildings, hybrid applications or replacements.

Still curious what all the fuss is about?

Learn from our experts what makes high-efficiency boilers different from conventional, or standard, boilers, and the impact they can make.

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EcoTec Control

Our high-efficiency boilers are tested and/or certified to the industry’s highest standards

Department of Energy

Department of Energy



AHRI – Air-Conditioning, Heating, & Refrigeration Institute

Air-Conditioning, Heating, & Refrigeration Institute

ASME – American Society of Mechanical Engineers

American Society of Mechanical Engineers

Department of Energy

Canadian Standards Association

Department of Energy

Underwriters Laboratories

ANSI – American National Standards Institute

American National Standards Institute



NFPA – National Fire Protection Association

National Fire Protection Association

SCAQMD – South Coast Air Quality Management District

South Coast Air Quality Management District

Let’s talk high-efficiency boilers

Share your questions or comments below and we will be in touch.


Frequently asked questions

Which are Weil-McLain’s best residential and commercial boilers?

This is a very good question! The “best” answer is the boiler that fits your application the best. We have many choices for water systems and generally the higher efficiency boilers like our Evergreen Gas Boiler will be right for the application. Steam systems will require a boiler that meets the heating load plus a small pickup factor. Commercial boilers are designed for larger heating loads, but the same criteria we used for residential systems apply: Use the boiler that best fits the application with efficiency in the forefront of the design.

What is Weil-McLain’s most efficient boiler?

Weil-McLain’s lineup of high-efficiency boilers is second to none. For residential water applications, our Evergreen Gas boiler tops the list. If a combi application is needed, our Eco Tec Gas Boiler is best. Commercial water system efficiencies will be enhanced by using our SVF stainless steel condensing boiler.

How much does a high efficiency boiler save?

Generally, high-efficiency boilers will cut fuel costs between 10 and 20 percent, based on system design and operating temperatures.

How efficient is a combi boiler?

Today’s combi boilers are state-of-the-art and have standard efficiencies at 95 percent or above. You can learn more about efficiency ratings here.

What factors affect boiler efficiency?

There are many factors that affect  boiler’s efficiency. First and foremost is water. Whether you have a steam or water system, the cleaner the water the higher your boiler efficiency will be. Another important factor is the tune of your combustion system. A properly tuned boiler will use less fuel, therefore increasing or sustaining the highest operational efficiency. You can learn more factors and tips for increasing energy efficiency here.