AO Smith Power Vent Water Heaters

A review of the AO Smith power vent water heaters from Vertex and ProMax series, including high efficiency and low NOx models.

AO Smith manufacturer offers over twenty tank-type, power vent gas water heaters that utilize the metal tank with capacities from 40 to 75 gallons and divided into two sizes: short and tall. All the models come from two groups: ultra-efficient Vertex and ProMax, powered by natural and propane gas.

AO Smith Vertex Power Vent

Vertex is the only super-efficient model from all AO Smith power vent water heaters capable of providing a thermal efficiency of over 90%.

Vertex is equipped with a 50-gallon tank and can continuously deliver over 92 gallons of hot water in one hour and a water flow of 3 gallons per minute.

The environment-friendly and top-fired gas burner helps the water heater reduce the emission of NOx gases and, together with the spiral heat exchanger, increases efficiency, saving energy and money.

The advanced electronics allow better and precise control of the water temperature and make troubleshooting easier.


ProMax is the widest group of all power vent gas water heaters whose energy factor ranges from 0.65 to over 0.7, making many of the Energy Star compliant (EF has to be higher than 0.67). ProMax models are available in 40, 50, and 75-gallon sizes and are grouped into three categories:

  • ProMax Power Vent
  • ProMax Ultra-Low NOx Power Vent
  • ProMax SL

ProMax Power Vent

ProMax Power Vent Higher EF are high-efficiency water heaters that are designed to maximize efficiency and performance. As the Energy Star approved, ProMax water heaters save money and time while protecting the environment with low NOx gas combustion.

The main features include the DynaClean II system and its specially designed dip tube for optimized water heating and protection against the sediment build-up inside the metal tank.

The most applied pilot light has been replaced by the hot surface ignitor, which is not only a more reliable feature but saves more energy.

The metal tank is protected with the Blue Diamond glass coating and factory-installed anode rod.

Power vent design brings great versatility as its vent pipes can be installed horizontally through the outside wall and vertically through the roof. Such enhanced flexibility brings you more options during the installation, especially with the 3-position rotatable blower outlet. The pipe can use various materials: PVC, ABS, or PP and can run up to 180 feet, making them perfect even in homes with the limited space.

The advanced gas control valve increases the accuracy in temperature control and makes diagnostic easier. The protected sensor and air intake snorkel enhance safety since the combined system prevents the accidental ignition of the flammable vapors.

Models and specs

Models / Specs GPVL 40 GPVT 40 GPVL 50 GPVT 50 GPVX 50L GPVX 75L
Capacity (Gal) 40 40 50 50 50 75
Gas input (BTU) 40,000 50,000 40,000 50,000 62,000 72,000
FHR (GPH) 73 90 90 96 110 155
Energy factor 0.7 0.7 0.7 0.7 0.7 0.68
Recovery rate (GPH) 44.7 55.9 44.7 55.9 69.3 80.4
Max. vent length (ft) 180 180 180 180 125 125
Weight (lb) 174 176 198 192 212 277

ProMax Ultra-Low NOx Power Vent

AO Smith power vent water heaters from the Ultra-low series utilize the advanced burner system that combines the radiant heat and access air to increase the energy efficiency to 0.68 while providing the gas combustion with the reduced amount of greenhouse gases.

The burner system uses high-quality materials and is more efficient and durable than the standard type.

The Ultra-low NOx water heaters are equipped with the Coregard anode rod and the DynaClean dip tube for protection against corrosion and sediment build-up. Ultra-low models utilize the FVIR system with the flame arrestor.

Models and specs

Models / Specs GPNH 40 GPNH 50
Capacity (Gal) 40 50
Gas input (BTU) 42,000 42,000
FHR (GPH) 69 81
Energy factor 0.68 0.68
Recovery rate (GPH) 42.6 42.6
Max. vent length (ft) 120 120
Weight (lb) 170 207

ProMax SL

Hybrid power vent water heater GPH 90N does not belong to the conventional type gas appliances, but it combines the best from tankless and tank-type technology resulting in high energy efficiency and First Hour Rating. The innovative technology includes the patented circulation system that ensures the best performance and other benefits.

Models and specs

Models / Specs GPVT-40L GPVT-50L GPVX-50L GPS-75L
Capacity (Gal) 40 50 50 75
Gas input (BTU) 50,000 50,000 62,500 80,000
FHR (GPH) 80 83 114 N/A
Energy factor 0.65 0.65 0.65 N/A
Recovery rate (GPH) 53 53 66 86
Max. vent length (ft) 160 160 120 100
Weight (lb) 166 186 186 245

All the models that comply with the Energy Star requirements, such as the High EF and Ultra-low NOx series, provide more energy and money savings than the SL series, which doesn't comply. The above models are factory-built to use natural gas, while propane models have the same specifications and warranty of 6 years.

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