AO Smith Gas Water Heaters
Review and Buying Tips

A review of top models from AO Smith gas water heaters and what features to look for. With over 100 different models, AO Smith manufacturers models for any household, from simple and affordable to environment-friendly, ultra-efficient, and Energy Star heaters, designed to save money, enhance your comfort, and protect the environment.

AO Smith gas water heater

All the gas models from AO Smith are found as tank-type and tankless, utilizing natural gas or propane, and are grouped into three categories:

  • ProLine - Good
  • ProLine Master - Better
  •  ProLine XE - Best

When it comes to size availability, gas models can be either tall or short, also with the tank capacity 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 the advanced technology and ultra-efficient operation are not needed and where features are not the most innovative as found in condensing.

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.

On the other side, the “best” models available from AO Smith are coming from the Proline XE series. 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 comes with the longest warranty, which can go up to 10 years.

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

The best of AO Smith - condensing

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 rate 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.

The condensing technology makes Vertex models with the highest thermal efficiencies of 90 and 96%, which makes 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 NOx, and high-efficiency gas burner and side taps for recirculation.

Polaris is another group of condensing tank-type water heaters which can produce hot water with the efficiency of over 90% which is similar to Vertex, but Polaris has 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, fantastic protection, they are also equipped with long-lasting stainless steel storage tanks and heat exchangers, which allows them 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 water heaters are equipped with the self-cleaning dip tubes, they can perform much better as there is less sediment built-up 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 its power from its minimum to its maximum, performing better, and providing savings, while protecting the environment.


Except for storing hot water inside the metal tank, 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 of the 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 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, while 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 what you should look for; Vertex and Polaris from the ProLine XE group. Or, tankless.


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