Best Condensing Tankless Water Heaters

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The article about best condensing tankless water heaters reviews the top manufacturers in water heating industry Noritz, Rinnai, and Navien and includes the most advanced features and benefits provided by the condensing technology.

Condensing water heaters are the most energy efficient gas heaters that are available today. The units utilize two exchangers; one that gets the heat directly from the gas burner and the other, which is made of stainless steel, that uses the residual heat from the flue gases (wasted energy). This is what increases the performance and efficiency while significantly reduces the emission of the greenhouse gases, saving greatly on energy too.

Since the flue gases are cooled down, every condensing water heater can use cheaper venting, usually made of PVC material, vs. more expensive stainless steel found in non-condensing units. The review of the best non-condensing tankless brands and models can be found here

The best of Rinnai

rinnai condensing rc98

The best condensing tankless water heater from Rinnai is coming from the RUR line, no matter is it an indoor or outdoor model. Rinnai RUR98i model is designed for an indoor and RUR98e for the outdoor installation, both working with the maximum power of 199,000 BTU and high flow rate of 9.8 GPM, making it ideal for homes with up to four baths. RUR indoor models are also unique in the industry because both concentric and PVC/CPVC venting are available on one unit.
Both models are coming from the Ultra series and have the ultra-low NOx emission and superior energy efficiency of up to 96% making them Energy Star compliant and eligible for rebates (where applicable).

The RUR series is different from other condensing models from Rinnai as it utilizes the recirculation system with or without the dedicated line and is comprised of the thermal bypass valve, internal bypass line and integrated circulation pump, all working together for faster hot water delivery time, less energy and water waste.

The best of Noritz

noritz condensing nrc111

The best of Noritz condensing tankless water heaters is coming from NRC111, a series with the amazing 11.1 GPM flow. Such a high water flow accommodates high demanding homes, with up to three showers working simultaneously or more, while its capability to be combined with the identical water heater through the Quick-Connect, bring twice as much of hot water.

Both indoor NRC111-DV and outdoor NRC111-SV are equipped with the dual flame burners for less fluctuation in the temperature and commercial-grade heat exchangers with a thicker piping, making it very resistant to stress and abuse.

The minimum water flow is higher (0.5 GPM) than the upper Rinnai models, so it needs more water flow before it starts.

Navien condensing water heaters

Navien NP-240

Navien condensing tankless water heaters are the most efficient heaters from this manufacturer. The energy efficiency they are providing is amazing 98%, and thanks to the Eco Three-phased Pre-mixed burner they reduce NOx emission drastically.

Navien utilizes two heat exchangers, both made of stainless steel which makes them more resistant to stress while providing longer life. The warranty is longer than on other brands, it is 15 years on the heat exchanger, vs. 12 on other brands.

With the two microprocessors built-in, Navien provides better control and safety while optimizing the best performance and giving its users hot water temperature with much less fluctuation.

Navien NPE-240 is the tankless water heater with the highest flow from this manufacturer, 11 GPM, and with the Ready Link System, it connects 16 units into one system, which makes it ideal for big houses demanding large volumes of hot water.

Another great benefit Navien offers is the air and gas pressure sensor which maximizes the combustion efficiency while making the combustion stable.


Condensing tankless water heaters are getting more and more in popularity because of the green technology and many advantages they offer. Designed as the next generation in tankless technology, the advanced technology brings the extremely high efficiency, high-performance level, less gas emission and energy savings.

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