In 2010, A. O. Smith introduced its full line of natural gas and propane tankless water heaters that continue to be an innovative part of the full A. O. Smith product family today. 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.


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Benefits of Gas Tankless Water Heaters

Washing hands under running water.

Continuous Hot Water

Gas tankless water heaters give you continuous hot water on demand. When paired with a recirculation pump, they provide guaranteed instant hot water.

Space Savings

A. O. Smith’s natural gas and propane tankless water heaters can be mounted inside or outside (depending on your region) to save space within your home.

Two babies in a bathtub.
Woman hugging a child wrapped in a towel.

Energy Savings

Gas tankless water heaters only heat your water when you need it, which can reduce energy costs. Paired with A. O. Smith’s 15-year tankless limited warranty, gas tankless models can be a smart, money-saving solution for your home.

A Closer Look

Diagram of the interior of a tankless water heater.

How Do Gas Tankless Water Heaters Work?

When a natural gas tankless water heater or propane tankless water heater is installed in your home, it is attached directly to the water line to deliver on-demand hot water. When you open a hot water tap, the water flow sensor within your water heater is triggered and the burner is activated. The water within your system begins to circulate through the heat exchanger, heating your water to the designated temperature and providing you with continuous hot water. Once you turn off your water tap, the unit shuts down to save energy.

Both tank and tankless water heaters have advantages depending on your specific needs.

Gas tankless water heaters will typically have a lower operating cost. Electric is a better option if you do not currently have natural gas or propane service. Also, electric is a great option for POU (point of use) applications like hand wash stations.

The primary advantages of gas tankless water heaters are energy savings, space savings, and continuous hot water. The downside is initial cost of the unit, which is often higher than other options. However, this initial investment is often paid back within the life of the unit due to the energy savings.

A. O. Smith tankless water heaters boast industry-leading warranties. While the lifespan of a gas tankless water heater can vary, factors like water conditions, usage rates and maintenance all contribute to your water heater’s health.

Tankless gas water heaters do use electricity. They use the standard 120V that is used in all homes.

What do I need?
Before installation, you will need to determine the incoming ground water temperature, the ideal location in your home, and the correct water heater size required for your needs.

Where to install?
A tankless water heater can be installed anywhere in your home with the correct piping—closets, garage, bathrooms, etc. In warmer climates where there is no risk of freezing, a tankless water heater may be installed on the exterior of the home to save on interior space.

While it is difficult to estimate an exact value, the popularity of tankless water heaters can improve the value of your home and time on market if you choose to sell your home.

A tankless water heater


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Learn more about A. O. Smith’s full line of condensing and non-condensing tankless water heaters.

A tankless water heater

Never Descale Again. Ever.

Introducing X3® Scale Prevention Technology on our Condensing Gas Tankless Water Heaters. Over 15 years Learn About Tankless with X3® Scale Prevention Technology life with no maintenance.

View All Tankless Models with X3® Learn About Tankless with X3® Scale Prevention Technology
Condensing tankless gas water heater

Condensing Gas Tankless with X3® Scale Prevention Technology:


Tank gas water heater

Non-Condensing Gas 50 Gallon Tank:


Single Shower Length* Unlimited 37 minutes
Showers Back-to-Back* Unlimited 4.7 showers
Showers at the Same Time* 3.1 showers 3.2 showers
Maximum Tub Size* Unlimited 87 gallons
X3® Scale Prevention Technology check_circle_outline
Continuous Hot Water check_circle_outline
Space Savings check_circle_outline
Energy Efficiency check_circle_outline
Hot Water Storage Supply check_circle_outline
UEF 0.93 0.62
Warranty 15 Years 6 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.
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Additional Reading

Contractor Resources

  • Screwdriver and wrench icon.

    Installation Guide

    Download our gas tankless water heater installation instructions.

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  • Set square icon.

    Resource Guide

    Match the flow rate to your customer’s needs.

    View Document
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    Cross Reference Tool

    Search for NAECA-compliant replacement options.

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