A. O. Smith has been a leader in whole-house water heating solutions for over 80 years. With the addition of electric tankless and gas tankless whole-house water heaters, A. O. Smith continues to deliver innovative products that are built to last.

A Closer Look

Diagram of the interior of a tankless water heater.

How Do Whole-House Tankless Water Heaters Work?

Whole-house tankless water heaters produced by A. O. Smith deliver hot water on demand and can help in reducing energy consumption for your home. Built with scale-reduction technology, both electric tankless and gas tankless whole-house water heaters perform with high efficiency and are built to serve a wide range of applications.

A whole-house tankless water heater is built to provide continuous hot water whenever you need it. When a hot water tap is turned on, water from your cold water pipe enters the water heater and passes through the heat exchanger. With an electric tankless product, the water passes over the heating elements, quickly heating the water to your desired temperature. The process is the same for a gas tankless water heater, but instead of heating elements powered by electricity the burner is fueled by a natural gas or liquid propane line. For all A. O. Smith tankless water heaters, a continuous supply of hot water is delivered to your home with ease.

Both tank and tankless whole-house water heaters have their advantages. Tank-type water heaters have a lower upfront cost and are often easier to install when replacing a similar type tank water heater. Although they have a higher upfront cost, tankless water heaters provide continuous hot water on demand, take up less space, and require less energy to operate.

The advantages of whole-house electric and gas tankless water heaters are potential lower energy usage, smaller space requirement, and continuous hot water. Although there may be a higher upfront installation cost for tankless there may be potential savings over time, depending on usage, local energy costs, incoming groundwater temperature, and other factors.

What is recommended for maintenance?
Most whole-house tankless units will require annual descaling of the unit, but with A. O. Smith’s built-in anti-scale technology, available in select models, your water heater’s life can be extended. The anti-scale technology helps change the chemical makeup of the scale so it will pass through the heat exchanger without sticking to the walls and negatively impacting the water heater’s performance.

A. O. Smith gas tankless models have a 15-year limited warranty, and the electric tankless models have a 5-year limited warranty. However, if properly maintained, a tankless water heater can last up to 20 years for gas tankless and 10 years for electric tankless.

Tankless water heaters help you save energy due to the unit only providing heat when you are using hot water, rather than heating the tank continuously when not in use.

Due to the growing popularity of tankless technology, adding a tankless water heater can certainly improve the appeal to a prospective buyer.

How much does it cost to install a tankless hot water heater?
The cost of installation can vary depending on the current plumbing of your home. A. O. Smith recommends contacting a licensed contractor to begin the evaluation process.

What size tankless water heater do I need for my house?
After evaluating your desired water supply, your home’s climate and current piping, a licensed contractor will be able to provide an exact recommendation for your home. Use the XPERT Product Selector to get an initial recommendation on which water heater would be right for your home.

Where should I install a tankless water heater?
Electric tankless water heaters can be installed in any location within your home with the appropriate hookups. Their compact size frees up valuable space within your home. For gas tankless water heaters you will need to utilize specific venting, which will impact where you can install throughout your home.

How do you vent a tankless water heater?
No venting is required for A. O. Smith whole-house electric tankless water heaters, but for gas tankless water heaters you will need to consult with your local plumbing contractor to determine the best venting for your home.

The one that fits your specific hot water needs! Talk with your installer about your specific energy options (natural gas, liquid propane or electric), usage requirements, and venting requirements to determine the option that best fits your needs.

Benefits of Tankless Water Heaters

  • Children washing hands.

    Continuous Hot Water

    Tankless water heaters deliver continuous hot water. If sized properly, you’ll never run out of hot water again.

  • Filling a glass of water.

    Energy Savings

    A. O. Smith tankless water heaters heat your water only when you’re using it, reducing energy costs depending on your hot water usage.

  • Father brushing teeth with daughter.

    Space Savings

    Due to their significantly smaller size, tankless water heaters save a tremendous amount of space compared to a traditional water heater and can be mounted in various spaces around your home.

  • Washing a dog with a hand-held shower.

    On-Demand Hot Water

    The heating technology within
    A. O. Smith tankless water heaters provides on-demand hot water by heating the water when you need it.

  • Mother helping children wash their hands.

    Instant Hot Water

    A. O. Smith tankless water heaters with built-in recirculation pumps offer instant hot water when installed with the proper piping.

  • Feet up relaxing in a bubble bath.

    Innovation & Reliability

    A. O. Smith has a long, rich history of reliability and innovations that have led the water heating industry for decades.

Tankless vs. Tank

Take a closer look at the advantages of each type of water heater.

A group of tankless water heaters

Tankless Water Heater

  • Continuous hot water
  • Energy efficient
  • Space savings
  • Environmentally friendly


A group of tank water heaters

Tank Water Heater

  • Low initial investment
  • Energy-efficient options
  • Easy installation
  • Wide range of tank sizes from 30 to 95 gallons
  • Hot water storage supply
A tankless water heater

Gas Tankless
Water Heater

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Learn about A. O. Smith gas tankless water heaters and if they are the right fit for your home.

Electric Tankless
Water Heaters

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Learn about A. O. Smith electric tankless water heaters and if they are the right fit for your home.

A tankless water heater
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Contractor Resources

  • Screwdriver and wrench icon.

    Installation Guide

    Download our gas tankless water heater installation instructions.

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    Resource Guide

    Match the flow rate to your customer’s needs.

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    Cross Reference Tool

    Search for NAECA-compliant replacement options.

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