Adapt®+ Premium Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt®+ Premium Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATHR-199X3 100

ENERGY STAR® certified (0.95 UEF)
199,000 BTU input
15-Year Warranty

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Adapt®+ Premium Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt®+ Premium Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATHR-180X3 100

ENERGY STAR® certified (0.95 UEF)
180,000 BTU input
15-Year Warranty

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Adapt®+ Premium Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt®+ Premium Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATHR-160X3 100

ENERGY STAR® certified (0.95 UEF)
160,000 BTU input
15-Year Warranty

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Adapt®+ Premium Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater

Adapt®+ Premium Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater Model ATHR-199M 100

ENERGY STAR® certified (0.95 UEF)
199,000 BTU input
15-Year Warranty

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Adapt®+ Premium Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater

Adapt®+ Premium Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater Model ATHR-180M 100

ENERGY STAR® certified (0.95 UEF)
180,000 BTU input
15-Year Warranty

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Adapt®+ Premium Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater

Adapt®+ Premium Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater Model ATHR-160M 100

ENERGY STAR® certified (0.95 UEF)
160,000 BTU input
15-Year Warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt® SC Standard Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATM-199X3-N 100

ENERGY STAR® certified with a UEF of 0.95
199,000 BTU input
15-year limited warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt® SC Standard Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATM-180X3-N 100

ENERGY STAR® certified with a UEF of 0.95
180,000 BTU input
15-year limited warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

Adapt® SC Standard Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATM-160X3-N 100

ENERGY STAR® certified with a UEF of 0.95
160,000 BTU input
15-year limited warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater

Adapt® SC Standard Condensing Ultra-Low NOx 199,000 BTU Natural Gas Tankless Water Heater Model ATM-199M-N 100

ENERGY STAR® certified with a UEF of 0.95
199,000 BTU input
15-year limited warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater

Adapt® SC Standard Condensing Ultra-Low NOx 180,000 BTU Natural Gas Tankless Water Heater Model ATM-180M-N 100

ENERGY STAR® certified with a UEF of 0.95
180,000 BTU input
15-year limited warranty

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Adapt® SC Standard Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater

Adapt® SC Standard Condensing Ultra-Low NOx 160,000 BTU Natural Gas Tankless Water Heater Model ATM-160M-N 100

ENERGY STAR® certified with a UEF of 0.95
160,000 BTU input
15-year limited warranty

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ProLine® XE Ultra-Low NOx Indoor 199,000 BTU Natural Gas Tankless Water Heater

ProLine® XE Ultra-Low NOx Indoor 199,000 BTU Natural Gas Tankless Water Heater Model ATI-540P-N 100

Endless Hot Water
199,000 BTU input
15-Year Warranty

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ProLine® XE Ultra-Low NOx Indoor 199,000 BTU Condensing Propane Tankless Water Heater

ProLine® XE Ultra-Low NOx Indoor 199,000 BTU Condensing Propane Tankless Water Heater Model ATI-540P-P 101

Endless Hot Water
199,000 BTU input
15-Year Warranty

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ProLine® XE Concentric Vent Indoor 199,000 BTU Non-Condensing Natural Gas Tankless Water Heater with X3® Scale Prevention Technology

ProLine® XE Concentric Vent Indoor 199,000 BTU Non-Condensing Natural Gas Tankless Water Heater with X3® Scale Prevention Technology Model ATI-510CX3 110

X3® Technology
Concentric Vent
15-Year Warranty

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Yes, A. O. Smith is an emerging tankless water heater manufacturer. Their gas tankless line includes ENERGY STAR® certified models with 0.95 UEF efficiency and innovative X3® Scale Prevention Technology that eliminates annual descaling maintenance. A. O. Smith offers Good, Better, and Best product tiers backed by 15-year warranties, with ultra-low NOx emissions and adaptable installation options supported by extensive professional installer networks.

Tankless water heaters have higher upfront costs and more complex installation than traditional tanks. They work best when hot water usage is staggered rather than simultaneous, as flow rate limits how many appliances can run at once. Gas models require proper venting and may need gas line upgrades. Larger homes may need multiple units, though modern features like X3® technology help minimize the maintenance concerns that previously affected tankless systems.

A. O. Smith stands out with over 80 years of innovation and the world's largest water heater factory in Tennessee. Their tankless line features proprietary X3® Scale Prevention Technology that eliminates annual descaling with an industry-leading 15-year warranty covering scale-related failures. A. O. Smith offers comprehensive Good to Best product tiers, extensive professional installer networks, and A. O. Smith University training for contractors. Their combination of advanced technology, warranty coverage, and professional support makes them a top choice for reliable water heating.

A. O. Smith gas tankless water heaters typically last 15-20 years with proper maintenance, significantly longer than traditional tanks. Life expectancy varies by type: traditional tank water heaters last 8-12 years, hybrid heat pump models last 12-15 years. Actual lifespan depends on water quality, maintenance frequency, installation quality, and usage patterns. Regular maintenance and proper professional installation help maximize lifespan for any water heater type.