Tankless Water Heaters from A. O. Smith

No tank. No maintenance. No limits. Just reliable hot water when you need it.

Tankless water heaters heat water on demand rather than storing it in a tank. This is different from traditional tank water heaters that keep 40-50 gallons of water hot around the clock, whether you're using it or not. Tankless systems only heat water when you actually need it, which can reduce energy costs and free up the floor space a storage tank would occupy.

A. O. Smith offers natural gas, propane, and electric tankless water heaters. These include whole-home systems that serve your entire household and smaller point-of-use units for individual fixtures like a remote bathroom or kitchen sink.

Find out what size water heater you need using our residential water heater selector.

Continuous Hot Water Supply

Tankless water heaters can provide hot water for multiple back-to-back showers when properly sized for your household's needs. However, the number of fixtures you can run simultaneously depends on the unit's flow rate—most residential models handle 2-3 showers at once.

Lower Energy Use

These systems only heat water when you're using it, not continuously throughout the day and night. ENERGY STAR® certified models with 0.95 UEF ratings (Uniform Energy Factor—a measure of how efficiently the unit converts fuel to hot water) meet federal efficiency standards and may qualify for tax credits.

Space Savings

A traditional tank water heater takes up about 16 square feet of floor space. Tankless units mount on the wall and are roughly the size of a suitcase. This frees up storage area in basements, utility closets, or garages. Depending on your climate and the specific model, you can install them indoors or outdoors. This flexibility can be helpful if you're working with limited space or specific installation requirements.

Longer Lifespan

Tankless water heaters typically last around 20 years with regular maintenance, compared to 10-12 years for traditional tank systems. A. O. Smith provides a 15-year warranty on our tankless models. The extended lifespan means fewer replacements over the time you own your home.

Condensing vs. Non-Condensing

Condensing tankless water heaters capture and reuse heat from exhaust gases that would normally vent outside. Some condensing units, like the ADAPT SC, use dual heat exchangers—one heats your water while the second captures exhaust heat. Others, like the ADAPT+ Premium, achieve high efficiency with a single heavy-duty stainless steel heat exchanger designed for superior heat transfer.

These models achieve 0.95 UEF efficiency ratings and carry ENERGY STAR® certification. They qualify for federal tax credits and use 2-inch PVC venting, which is generally simpler to install than larger metal venting systems.

Non-condensing models have a single heat exchanger and operate at 0.82 UEF efficiency. They cost less initially but don't recapture exhaust heat. These work well as entry-level options or in situations where the higher efficiency doesn't justify the additional cost.

Whole Home vs. Point-of-Use

Whole-home tankless systems are designed to serve all your household's hot water needs from one central location. Gas models typically range from 140,000 to 199,000 BTU and can handle multiple showers, appliances, and fixtures running simultaneously.

Point-of-use models are smaller electric units installed near individual fixtures. These make sense for locations far from your main water heater—a bathroom addition, a workshop sink, or a kitchen in a different part of the house. Hot water arrives faster because it doesn't have to travel through long pipe runs.

Hard water contains minerals like calcium and magnesium. In most tankless water heaters, these minerals build up inside the heat exchanger over time. This scale buildup reduces efficiency and restricts water flow.

A. O. Smith's X3® Scale Prevention Technology addresses this differently. The system uses a patented cartridge built into the water heater that prevents scale formation before it starts. The cartridge doesn't require replacement, and the annual descaling appointment isn't necessary.

This technology can extend the operational life of your water heater by up to 300%. A. O. Smith provides a 15-year warranty covering scale-related failures on units with X3® technology. While some other manufacturers offer external scale prevention systems that require additional plumbing, X3® is integrated directly into the unit.

For more information, refer to our tankless water heater buying guide.

The ADAPT® name reflects what makes these systems unique: adaptability. These tankless water heaters adapt to virtually any installation scenario with indoor or outdoor mounting options, advanced 2-inch venting that simplifies installation, and half-inch gas line capability (while many competitors require three-quarter-inch lines). Whether you're replacing an existing unit or installing in new construction, ADAPT® systems work with your home's setup rather than requiring major modifications. The current ADAPT® series includes three tiers designed for different needs and budgets.

Gas tankless water heaters require professional installation. The work involves proper gas line sizing, venting that meets local building codes, and electrical connections for the unit's controls.

A. O. Smith works with certified contractors who understand local code requirements and have experience with ADAPT® models. ADAPT® systems are designed with installation considerations in mind: 2-inch venting options, half-inch gas line capability, and both indoor and outdoor mounting options.