Best Condensing Water Heaters
Review and Buying Tips
(updated 2017)

Explore the best products for home water heating - condensing water heaters, from the conventional storage tank and tankless group. Check out how selected condensing models provide ultra efficient water heating resulting in great savings of over 50%, high energy factor of up to 0.97 and Energy Star compliance for additional incentives.

Compare Rinnai, Noritz and Navien tankless water heaters and AO Smith Vertex and Polaris using the conventional tank type design.

Residential gas-powered condensing water heaters are very popular in Europe, where they are usually called condensing boilers, combi boilers and cylinders. And, for example, in UK, combi boilers are found in close to 70% of homes.

These are also well-known in North America for commercial use... and because of all the benefits, rising gas prices and lower operating costs, condensing water heaters are becoming more and more popular in residential water heating applications as well.

Also the government legislation and higher demand for the energy efficient water heating systems, are making the condensing heaters a favorable gas type.

Best tankless condensing water heaters

What makes the condensing water heaters with the tankless design unique are two heat exchangers, usually made of stainless steel, where the secondary element is added to capture the heat energy from flue gases and preheat the incoming cold water, increasing the efficiency to over 90%. Due to the tank-less design water is just passing through the heat exchanger, generating hot water with no storing and on demand.

The best condensing and tankless water heaters are coming from the popular brands; Rinnai, Noritz and Navien.

Rinnai RUR98i

Rinnai RUR98iRinnai RUR98i

From Rinnai manufacturer, an indoor water heater RUR98i is probably the best. Model RUR98i is the most powerful unit with the highest water flow rate of 9.8 GPM and efficiency of 0.95 -  ideal for demanding families. The exclusive ThermaCirc360 feature makes it great as the unit can be used in recirculation to deliver hot water fast and therefore save on energy, reducing the wait time and increasing the comfort.

An advanced electronics and eco-friendly gas burner, combined with the modulating gas valve, allows this unit to operate from its minimum to the maximum of 199,000 Btu, generating ultra low NOx gas emission. It comes with the warranty of 12-years.


Noritz NRCP1112

Noritz NRCP1112Noritz NRCP1112

The best of Noritz is a direct vent model NRCP1112 built for indoor installations only. NRCP1112 is a condensing water heater that produces high hot water flow of 11.1 GPM making it great for large homes with up to 4-5 baths, and with the energy factor of over 0.9 providing savings over 50%.

Noritz NRCP1112 is equipped with the internal circulation pump which has two modes to reduce the wait time for hot water while saving water and energy. The advanced electronics and large control panel interface allows users to take advantage of the heater's programming and diagnostic system, to control, monitor and troubleshoot if there is a problem with the water heater.

The water heaters comes with the a 12-year warranty.


Navien NPE-240A

Navien NPE-240ANavien NPE-240A

Navien NPE-240A is the premium condensing water heater, one of the largest models from this Korean manufacturer, capable to provide endless supply of hot water with the high flow rate of 11.2 GPM and amazing efficiency of 0.97. And for the high demand applications a cascade system can be utilized so multiple units can be connected and operated by one controller.

Navien NPE-240A is equipped with the ComfortFlow Technology to eliminate the fluctuation of the water temperature or cold water sandwiches. The built-in recirculation system ensures faster hot water delivery while the Intelligent Preheating Technology recognizes the pattern usage, all working toward increasing the comfort and overall satisfaction. It comes with the warranty of 15 years.


Best tank-type condensing water heaters

Video: AO Smith Vertex

As opposed to tankless, tank-type condensing water heaters are equipped with one super performing helical heat exchanger, which is completely surrounded by water. Good examples are AO Smith Vertex and American Polaris, both utilizing fully-condensing design that ensures high thermal efficiency of 96% and performance that rivals much larger heaters.

Polaris condensing water heater when compared to the same 50-gal size of Vertex, is lighter, more powerful - 199,000 Btu vs. 100,000 Btu; has much higher recovery rate of 253 vs 129 gallons and longer warranty of 10 years vs. 6-year warranty of the Vertex, but it costs more.

The flue spirals around and inside the tank so that the combustion gases spend more time releasing the heat until the water vapor in the gas - a natural by-product of the combustion process - condenses, releasing even more energy. The spot where the flue exits the tank is barely warm to the touch.

Another quality component include the metal fiber burner that is ultra resistant to stress and corrosive water effect. It is located in the sealed combustion chamber where it is capable generating very clean and high-intensity blue flame, resulting in less pollution but intensive heat transfer.

How condensing water heaters work

Condensing water heaters are gas-fired units with the similar water heating process as conventional models. The problem with the conventional heaters, the most popular heating systems in America and Canada, is that too much heat energy is wasted when the products of combustion - flue gases, are vented out.

Very smart solution comes with the condensing and energy efficient water heaters where the heat of the flue gases is recaptured and used for preheating of the cold incoming water, so less heat energy is wasted. These models achieve ultra efficiency by removing the heat from the burning fuel while cooling the products of combustion resulting in cheaper venting usage.

That is why the condensing boilers have to have larger and more efficient heat exchanger than traditional boilers including some other additions.

The water vapor produced by the burning of gas in the boiler, condenses back into liquid water, releasing the latent heat of vaporization from the water. Because latent heat is a significant source of energy, condensing boilers have efficiency ratings up to 98%.

Buying tips and benefits

  • Condensing water heaters are ultra efficient, expensive but have lower operating costs
  • The installation is more complicate and requires more skills and time, also for troubleshooting and maintenance
  • Tank type models have the first-hour rating much higher than conventional heaters, with the same capacity. That means smaller unit will provide as much hot water as the larger but less efficient model
  • Ideal for high demanding homes
  • Utilize less expensive PVC venting due to the lower temperature of the exhaust gases
  • No need to buy a larger tank type heater, as you are getting better performance with condensing hot water heaters
  • When comparing these condensing heaters with over 90% thermal efficiency, to conventional tank-type, which are with 80% of thermal efficiency, the expected energy saving is at least 10%.
  • The condensing boilers are one of the most environmentally friendly heating systems, with the reduced CO2 and NOx emission

Condensing water heaters are expensive but have lower operating costs, can perform much better (up to 40%) than their standard counterparts and are equipped with the most innovative features and technology - making them a good buy and long term investment.

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