AO Smith Gas Water Heaters
Review and Buying Tips

A review of the best AO Smith gas water heaters and features to look for. Explore the most efficient heaters, models with on-demand water heating, condensing technology, advanced diagnostics, and ultra-low gas emission.

AO Smith gas water heater

With over 100 different types and models, AO Smith manufactures water heaters for any household type, from simple and affordable to environment-friendly, ultra-efficient, and Energy Star heaters, designed to save money, enhance your comfort, and protect the environment.

This overview will cover two of the most popular types: gas tank-type and gas tankless, including popular condensing models from Vertex and Polaris.

AO Smith gas water heater

All gas models from AO Smith are designed as tank-type and tankless, heating water and storing inside the metal tank or running it through the heat exchanger for on-demand heating. Gas models are mostly built and sold with the natural gas option, but there are also propane models for those who are not connected to the natural gas pipeline - using propane tanks.

There are three main categories:

ProLine – GOOD – affordable and short 6-year warranty

ProLine Master – BETTER – affordable, efficient, and longer 8-year warranty

ProLine XE – BEST – premium features, high efficiency, condensing, and superior performance

When it comes to size selection, gas models for residential whole-house water heating are available as tall and short, offering tanks with capacities from 30 to over 75 gallons, giving more options to the homeowners.

Depending on the element quality, the manufacturer provides three types of warranties: 6, 8, and 10 years for tank-type and 15 years for tankless.

Water heaters from the ProLine and ProLine Master series are recommended for households where advanced technology and ultra-efficient operation are not required. As the features are not the most innovative as found in condensing, these heaters are affordable and suitable for smaller and average homes.

Most of these heaters have atmospheric and direct venting systems, including eco-friendly gas burners, Intelligent Control Logic, enhanced brass drain valves, and push-button piezo ignitors. These are built mostly for residential homes, while some are available for mobile homes as well.

If you are looking for the top-of-line gas models, check out those from the Proline XE series - promoted as the “BEST”. These gas models are the most powerful, have ultra-high-energy factors and very low pollution, and provide hot water with high recovery and first-hour rating.

These models include premium features such as the advanced gas valve, diagnostics system, hot surface, LCD display, two heavy-duty or one powered anode, and a self-cleaning system. They are available as power vent, ultra-low NOx, power direct vent, and atmospheric with the flue damper. Heaters come with the longest warranty, which can go up to 10 years.

When talking about the tankless type, users also have an option to get a cheaper non-condensing type with an efficiency of around 0.82 or condensing, whose efficiency goes above 90% and includes state-of-the-art features.

The best of AO Smith - condensing

Vertex models

AO Smith Vertex power vent and power direct vent are two of the most popular and probably the best gas water heaters from AO Smith. They are available in two sizes - 50 and 75 gallons and have high thermal efficiencies and delivery rates for the continuous flow of hot water. With the maximum gas input of 76,000 and 100,000 BTU, AO Smith Vertex models can deliver lots of hot water - up to 119 gallons making it ideal for high-demanding homes.

Condensing technology makes Vertex models generate lots of power with the highest thermal efficiencies of 94% and 96%, making them Energy Star compliant. Vertex heaters are equipped with the most advanced features; an ultra-efficient helical coil heat exchanger, two anode rods for better rust protection, sophisticated diagnostic tool, hot surface ignitor, low and ultra-low NOx gas emission, high-efficiency and eco-friendly gas burner, and side taps for recirculation and combined water and space heating.


Polaris series is another group of condensing tank-type water heaters that can produce hot water with an efficiency of around 96%, which is similar to Vertex. Still, Polaris has more models available and a much higher first-hour rating and recovery rate. For example, a 34-gallon model GSP 100 has a first-hour rating of 179 gallons and a recovery rate of 129 GPH.

Except for the innovative electronics and fantastic protection, they are also equipped with long-lasting stainless steel storage tanks and heat exchangers, allowing long-term service. Polaris has a longer warranty than Vertex: 10 vs. 6 years.

Features review

Gas control valve. A gas control valve has a microprocessor built-in to provide better operation and control, resulting in better accuracy, efficient and reliable service, savings, and simpler diagnostics.

Self-cleaning dip tube. As the gas water heaters are equipped with self-cleaning dip tubes, they can perform much better as less sediment is built inside the tank and on the elements.

Tank protection. Water storage tanks are protected from corrosion utilizing the Blue-Diamond commercial-grade glass coating and anode rods with a stainless steel core.

Gas burner. Look for the heaters with the eco-friendly gas burner with the modulation. These heaters can adjust their power from its minimum to its maximum, perform better and provide savings while protecting the environment.


Model/Feature Vertex GPHE-50 Vertex GDHE-50 Polaris GTP 199
Capacity (gal) 50 50 50
Power (BTU) 76,000 100,000 199,000
Efficiency 94% 96% 96%
First Hour Rating (GPH) 119 100 N/A (Recovery rate 253 gal)
Size (inch) 71x21 67x22 64x22
Simultaneous showers 2 2 3
Shower time 65 min endless endless
Warranty (years) 6 6 10


Storing and heating water inside the metal tank is the popular way of getting water, but AO Smith gas water heaters can also heat water on demand using tankless technology.

Tankless heaters heat water on demand, supplying hot water to multiple applications simultaneously and in an endless amount. There are two types; non-condensing with an efficiency of around 0.82 and condensing with an efficiency of above 90%, providing much better savings than most tank-type heaters.

Check out our review of AO Smith tankless here.


Heating potable water with natural gas is the most popular way of getting hot water at home. As the gas type is more powerful than the electric type and has a better recovery rate and first-hour rate, a family of four should use a model with a tank size of 60-70 gallons. If you decide to go with the high recovery models, you can even select a model with a smaller tank.

Most of the standard (conventional) types of heaters are low efficient, where the energy factor is around 0.6.

In contrast, high efficiency or condensing, as described above, have much better features and technology that heats water with the reduced energy loss and gas emission. That is why we recommend buying advanced models such as; Vertex and Polaris from the ProLine XE group or tankless.


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