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

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X3 Water Heater

How Does a Condensing Tankless Water Heater Work?

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 heater can provide years of hot water for your home.

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.

A tankless water heater can last up to 20 years, depending on your incoming water quality, usage, and maintenance.

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.

Condensing tankless water heaters are highly efficient and are ENERGY STAR® certified. The condensing models are also engineered for ultra-low NOx emissions to meet California's strictest emissions standards.

Does a tankless water heater need a drain?
A condensing tankless water heater will need a condensate drain, while a non-condensing water heater will not.

How do I keep my tankless water heater from freezing?
All A. O. Smith tankless water heaters have built-in freeze protection. However, if the heater is installed outdoors, during a power outage you will need to drain the water from the unit to prevent freezing.

While not overly complicated, it is recommended to use a licensed plumber or contractor to ensure proper installation. This protects against improper gas line sizing and venting which contribute to safety and performance. For these reasons, the 15-year limited warranty is only valid if installed by a credentialed installer.

Benefits of Condensing 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.

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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A dog being washed in a bathtub.

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.

Condensing tankless gas water heater

Condensing Gas Tankless with X3® Scale Prevention Technology:


199,000 BTU

Non condensing Tankless gas water heater

Non-Condensing Gas Tankless:


199,000 BTU

Single Shower Length* Unlimited Unlimited
Showers Back-to-Back* Unlimited Unlimited
Showers at the Same Time* 3.1 showers 2.6 showers
Maximum Tub Size* Unlimited Unlimited
X3® Scale Prevention Technology check_circle_outline
Continuous Hot Water check_circle_outline check_circle_outline
Space Savings check_circle_outline check_circle_outline
Energy Efficiency check_circle_outline check_circle_outline
UEF 0.93 0.82
Warranty 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.
A tankless water heater

Never Descale Again. Ever.

Introducing X3® Scale Prevention Technology on our Condensing Gas Tankless Water Heaters. The industry's first peace of mind, scale inclusive, 15-year warranty.

View All Tankless Models with X3® Learn About Tankless with X3® Scale Prevention Technology
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