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High Efficiency Condensing and Non-Condensing Gas Tankless Water Heaters

Engineered to deliver continuous hot water when you need it, propane and natural gas tankless water heaters are easily installed in tight spaces, including closets, bathrooms and even outdoors in appropriate climates.

high efficiency tankless water heaters

Residential High-Efficiency Condensing Gas Tankless Water Heaters

A. O. Smith's condensing natural gas and propane tankless water heaters are highly efficient. Available in both indoor and outdoor configurations, A. O. Smith's tankless models pair high efficiency with groundbreaking designs.

The new Adapt premium gas tankless hot water heater image made to look like a swiss army knife.


Ultra Flexible. Fewer Trips. More Savings.

Introducing the new Adapt™ Premium Condensing Gas Tankless Water Heaters with X3® Scale Prevention Technology.

Rebates & Tax Credits

Up to $850 in Local Utility Rebates may be available in your area!

*Gas water heaters with UEF of 0.82 or higher OR with a thermal efficiency of at least 90%. Local utility rebates available in limited geographical areas. For information on the Federal Tax Credit, go to: energystar.gov. Check with your tax advisor for applicability. Offer details and expiration may vary. See Rebate Center for details.

What Our Customers Are Saying

Benefits of Condensing Gas Tankless Water Heaters

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Continuous Hot Water

Condensing gas tankless water heaters produce continuous, on-demand hot water for your home and can provide instant hot water when the model includes a recirculation pump.

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Space Savings

A. O. Smith’s condensing tankless water heaters can be mounted in small or tight places both inside and outside of your home to better utilize and save space.

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Energy Savings

Condensing tankless water heaters utilize the residual heat from the exhaust gases to make hot water. That higher efficiency operation means lower operating costs and energy savings.

How it Works

Adapt tankless water heater cutaway with visible internals

A condensing tankless water heater saves space and supplies continuous hot water for your home, but what separates a condensing unit from a non-condensing unit is its ability to utilize excess heat efficiently by using a second heat exchanger that increases the efficiency and produces more hot water. Because tankless water heaters do not store their water supply within a tank, water is heated rapidly when the water runs through the heat exchanger within the tankless unit. Condensation is formed when you use a second heat exchanger to capture and cool what would otherwise be wasted heat. This process of utilizing the excess heat rather than venting it out of the heater allows your condensing tankless unit to conserve more energy, resulting in a Uniform Energy Factor (UEF) of over 0.90 and producing more hot water than non-condensing tankless heaters. Paired with a 15-year limited warranty, an

A. O. Smith condensing tankless water heaters can provide years of hot water for your home.

Still Have Questions?

A condensing gas tankless water heater uses condensing technology for energy efficiency. Similar to a non-condensing model, it heats water through a heat exchanger only when it's needed, instead of storing it in a tank. However, a condensing water heater is equipped with a second heat exchanger to boost efficiency and performance. It captures 95% of the heat produced, recycling this energy to heat more water instead of venting it outside of the heater. A condensing gas tankless water heater only releases vapors that have cooled to the point that they're not useful for heating.
Traditional water heaters are non-condensing, venting hot water vapor outside of the home along with combustion gasses. A condensing water heater is more efficient, keeping more of this heat inside the tank and recycling it to heat more water. While condensing tankless water heaters may have a higher upfront price per unit, their higher energy efficiency allows you to achieve cost savings over time. Total installation cost can differ, depending on your specific venting requirements.
Tankless water heaters offer the option of venting through an exterior side wall instead of through a chimney flue on the roof. Water heaters that are direct venting have two vents — one that pulls in air from the outside and one that carries away exhaust. Power venting water heaters draw air from inside the room and have only a single vent for exhaust. While non-condensing tankless water heaters require thick metal venting to handle the temperature of heat that's released, condensing tankless water heaters can use plastic venting such as PVC. They have already used the hot vapors to heat more water, leaving only cooler fumes for ventilation.

Our tankless water heaters come with a competitive 15 year limited warranty. Life of a unit may depend on your incoming water quality, usage, and maintenance. Hard water can leave mineral deposits on the heat exchanger and reduce its efficiency. You can extend the life of a condensing tankless water heater through regular maintenance and servicing, which includes cleaning and replacing filters, checking the burners and flushing mineral buildup. Many new A. O. Smith condensing gas tankless water heaters come with X3® Scale Prevention Technology that eliminates the need for regular descaling and extends the unit’s life up to three times.

The proper size of a tankless water heater depends on a number of variables, including type of appliances you own, number of people in your home, and incoming water temperature. You should discuss with your installer, but you can also consult our online XPERT™ Product Selector that can also be found as a downloadable app.

Product Comparison

Adapt XE
Standard Non-Condensing Gas Tankless Water Heater
Adapt XE Premium Condensing Gas Tankless Water Heater with X3® Technology
Standard Non-Condensing Gas Tankless Water Heater
Adapt Premium Condensing Gas Tankless Water Heater
Single Shower Length
Showers Back-to-Back
Showers at the Same Time
2.6 showers
3.1 showers
Maximum Tub Size
X3® Scale Prevention Technology
Continuous Hot Water
Space Savings
Energy Efficiency
Hot Water Storage Supply
15 Years
15 Years

*Many factors affect the actual performance of a water heater. This represents our closest approximation of your likely experience with this water heater in your local area, but actual performance may vary depending on factors beyond our ability to control or estimate.

Plumbing Professional

Get it installed by a Local Pro

A. O. Smith water heaters are available through your local plumbing professional.

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Why A. O. Smith?

Market Leader

A. O. Smith is a leading manufacturer of both residential and commercial water heating technologies, including the #1 most specified commercial water heater.

Commitment to Innovation

For more than 145 years, we’ve developed state-of-the art products that push new boundaries and improve the lives of our customers.

Best-In-Class Support

We combine cutting-edge technology with committed people who take pride in providing the very best support for our customers.

Unmatched Quality

Our products are put through rigorous quality and endurance testing so now matter where hot water is needed, A. O. Smith can provide a solution you can count on.

Learn more about A. O. Smith