Compare Tankless Water Heaters: Buyer's Guide to Best Models

Tankless water heater - Rinnai RUR199Tankless water heater

Compare tankless water heaters and find the best model for all your hot water needs. The review covers several popular brands and available models designed for point-of-use and whole-house water heating in residential applications.

We review the top manufacturers of tankless water heaters such as Bosch, Rheem, Rinnai, Noritz, and Takagi, compare the benefits and main features, and extract what is specific for that particular model.

Compare tankless water heaters: Things to consider

While we were reviewing and comparing tankless water heaters we have found many standard features and benefits:

  • Tankless heat water on demand and deliver hot water in endless supply to point-of-use and whole-house applications.
  • The lifespan of tankless water heaters is around 20 years.
  • The majority of the parts are replaceable and recyclable.
  • All the presented tankless water heaters are highly efficient with the energy factor, EF, of 0.82 or higher. Condensing is ultra-efficient with an EF of over 0.9.
  • All the models are Energy Star qualified.
  • The best tankless use the latest innovative engineering with the "green" technology that can increase performance and efficiency while reducing greenhouse CO2 and NOx gas emission.
  • All the tankless heaters utilize a direct electronic ignition.
  • Great user protection with safety features like flame failure, overheat, power failure, freeze protection, and others.
  • All the models have superior quality.
  • Designed to burn natural and propane gas.
  • The maximum input power they got is around 199,000 BTU. The turndown ratio is at least 10:1.
  • All the models include the remote controller or control panel with the digital display.
  • Long vents and use of PVC pipes.

Rinnai tankless water heaters

Buy the Best of Rinnai

The Rinnai manufacturer offers quite an extensive line of tankless water heaters utilizing simple on-demand and condensing technology for residential and commercial use.

Rinnai V (HE series) and RL models (HE+ series) are economy and non-condensing models that are used mainly in small and medium-size homes, where high demand for hot water is not required. While they have a higher energy factor than the tank-type, ranging between 0.79 and 0.82, they are not considered as Energy Star.

Tankless water heaters from the V series are also the simplest models that do not have voice activation capability, isolation valve for easy service, or Circ-logic option for fast hot water delivery, as the RL series.

Both V and RL series utilize one heat exchanger, integrated temperature controller, and flexible venting options. Models are available in both natural gas and propane.

Rinnai RUCS and RUS models (SE series) are coming from the condensing group, which gives them the ability to heat water with higher efficiency of close to 0.9, making them Energy Star compliant, but like the V series, these tankless models do not include a voice control system, isolation valve, and Circ-logic option. They also lack a decent size of the temperature display.

The most advanced models are coming from the RUC, RU, and RUR series, so they include all the best features that Rinnai offers. Also, all the models are ultra-efficient with an energy factor of over 0.9, which makes them Energy Star approved.

The ThermCirc360 technology makes the RUR series unique, so recirculation is possible with or without a dedicated line.

All the models use the Wi-Fi option for remote control and monitoring.

Rinnai RUR199i

Rinnai RUR199iRinnai RUR199i

Rinnai RUR199i and RUR199e are the largest indoor and outdoor models from Rinnai that can provide hot water to up to six features simultaneously.

Features highlights:

  • Cutting-edge technology guarantees maximized performance, efficiency, comfort, and savings.
  • ThermCirc360 technology comes with a built-in recirculation pump, timer, and thermal bypass valve so the users can get hot water almost instantaneously.
  • Rinnai Circ-Logic technology allows you to set recirculation patterns as you wish.
  • Ultra-low NOx gas emission, so it complies with some strict rules.
  • The high water flow of up to 11 GPM ensures reliable delivery to multiple applications in any home size.
  • Alexa voice integration and voice activation increase comfort and convenience.
  • Wi-Fi monitoring allows remote maintenance and diagnostics.
  • Use the smartphone for remote activation and schedules.
  • With an energy factor of 0.96, Rinnai RUR199 is Energy Star compliant.
  • Modulating gas valve allows power modulation from 15,000 to 199,000 BTU.
  • The maximum vent length is 150 ft. using either concentric or twin pipe setup.
  • High altitude options up to 10,200 ft.
  • Certified for mobile home installation.
  • A commercial-grade heat exchanger.
  • An integrated digital controller is available with the error code indicator.
  • Integrated condensate collector on the indoor model.
  • Available models: indoor, outdoor, powered by natural gas and propane.
  • Warranty: 15 years on the heat exchanger and 5 years for other elements.

Rheem tankless water heaters

There are two main groups of Rheem tankless water heaters: condensing and mid-efficiency.

Condensing models are further divided into Professional Prestige, Performance Prestige, and Performance Platinum group. Customers can get a tankless water heater that produces hot water with a flow rate ranging from 8.4 to 11 GPM, an efficiency of over 90%, and power ranging from 157,000 to 199,000 BTU. The size of the model you need depends on how many applications you want to use at the same time. No matter which one you choose, keep assured that you are getting models with the most advanced features and cutting-edge technology which will bring the highest efficiency and savings.

When talking about the Mid-Efficiency series, there are two groups; Tankless Mid-Efficiency and Performance Mid-Efficiency, both offering three sizes where the water flow goes from 7.0 GPM to 9.5 GPM and maximum power from 160,000 to 199,900 BTU. The maximum Energy Factor on the Rheem Mid-efficiency tankless water heaters is 0.82, lower than condensing but still providing substantial savings when comparing to tank-type. The main difference is that condensing has two heat exchangers, while this group has only one.

Rheem Professional Prestige 11.0 GPM - RTGH-RH11DVLN


Rheem RTGH-RH11DVLN models (indoor and outdoor) are the most advanced tankless and condensing water heaters from this North American manufacturer. As the above Bosch, it comes with an energy efficiency of over 90%, environment-friendly gas burner, and recirculation for fast hot water delivery.

Features highlights:

  • Eco-friendly gas burner with ultra-low NOx gas emission.
  • Dual stainless steel heat exchangers.
  • Built-in recirculation system reduces the wait time for hot water to almost instant.
  • Gas input is in the range from 18,000 to 199,000 BTU.
  • The maximum water flow of 11 GPM makes it ideal for high demanding applications.
  • The unit allows programmable time-based activation.
  • Excellent performance up to 8,400 ft. elevation.
  • Compatible with EcoNet for smart home management, including leak detection, gas, and water usage reports including maintenance reminders.
  • Wireless remote to control the temperature of the hot water.
  • Intelligent electronic system and self-diagnostic program.
  • Long PVC vents of up to 100 feet.
  • Compatible with the ½” gas line.
  • 12-year warranty on the heat exchanger and 5 years on other replacement parts for residential installations.

Noritz tankless water heaters

Noritz, a Japanese manufacturer of tankless water heaters, offers three categories of devices for residential water heating, supporting different home sizes and customer needs.

The Noritz NR series is recommended for homes with moderate usage or homes with up to 3.5 baths. While they can get a power of 199,900 BTU and a water flow rate up to 9.8 GPM, they are considered as mid-efficient models whose energy factor is around 0.81. They utilize only one heat exchanger.

The Noritz EZ series is the best to use when replacing a tank-type water heater of 40, 50, and 75 gallons while retrofitting an existing water heating system. The top-mounted connections, for example, make the transition easier, faster and cut the cost and time. EZ models use two stainless steel heat exchangers and condensing technology.

NRCB combination boilers are ideal for those homeowners who would like to heat both space and domestic water at the same time. All the models are condensing, so they can heat water with extremely high efficiency without polluting the environment as the standard type.

The Noritz NRCP line of tankless water heaters is the group offering cutting-edge technology for ultra-efficient heating. The condensing models use an internal pump for water recirculation for faster hot water delivery. As the above models, they are also Energy Star and can deliver hot water in large volumes.

Noritz NRCP1112

Noritz NRCP1112 tankless water heaterNoritz NRCP1112

Noritz NRCP1112 is the residential condensing and tankless water heater with the built-in recirculation pump with two modes – with and without the return line. It allows shorter delivery time of hot water and a better user experience.

Features highlights:

  • With the powerful gas burner that can generate 199,000 BTU and two heat exchangers, the NRCP1112 model can provide a high 0.94 energy factor and 11.1 GMP water flow, making it great for bigger homes or homes with up to 4.5 baths.
  • It is Energy Star compliant with ultra-low gas emission.
  • A dual heat exchanger.
  • Energy factor of 0.94.
  • Ultra-low NOx.
  • Water flow in a range from 0.5-11.1 GPM.
  • Modulating power ranging from 18,000 to 199,000 BTU.
  • Built-in temperature controller adjusting the temperature between 100 and 140 F.
  • Many safety features such as; flame sensor, overheat cut-off limit, gas leak detector sensor, water leak detector sensor, exhaust temperature sensor, water temperature sensor.
  • Recirculation compatible.
  • Self-diagnostic onboard computer system.
  • 12-year warranty on the heat exchanger and 5 years on other replacement parts for residential installations.

Bosch tankless water heaters

The Bosch Group is a reputable German manufacturer of Bosch tankless water heaters for residential and commercial use.

There are several models available to the consumers, which include non-condensing and condensing models grouped in the Therm and Greentherm series.

Greentherm 9000 series is the newest line of seven condensing and tankless water heaters that come with state-of-the-art engineering, superior energy efficiency, exceptional performance, and long life.

The Therm series includes several models:

Therm C 1210 ES is the condensing model which offers the power of up to 225,000 BTU, a high water flow of 12.1 GPM, and an efficiency of up to 98%. For the high-demanding homes, an Intelligent Cascading allows the combination of up to 24 units into one system.

Therm 940 ES and 830 ES are two of the smallest and non-condensing models offering the maximum efficiency of 83%, resulting in savings up to 50% on utility bills. Both are suitable for residential and commercial applications.

Bosch Greentherm 9000 series

Bosch 9000 tankless water heaterBosch 9000

Bosch Greentherm T9900I (SE 199) is the most powerful residential tankless water heater from this manufacturer, with the highest performance and water flow. It is small, lightweight, but ultra-efficient due to its condensing technology.

Features highlights:

  • Tankless and condensing technology.
  • Ultra-high energy factor of 0.96.
  • The water flow of 11.2 GPM.
  • Two heat exchangers; secondary made of stainless steel.
  • Ultra-low NOx gas emission makes the Greentherm SE 199 "green."
  • Built-in recirculation pump provides hot water instantaneously.
  • Built-in touch screen to adjust the temperature and for diagnostics.
  • Top connections and integrated drain ports for easy and convenient installation and service.
  • Integrated Wi-Fi allows remote control using the mobile phone. You can remotely control the temperature, set the system into the recirculation mode and monitor usage and other parameters.
  • Integrated sensor technology makes Auto tuning easy, ensuring optimal performance.
  • Modulating gas valve for improved combustion.
  • Energy Star compliant.
  • High turndown ratio of 22:1.
  • It is built for indoor and outdoor use without purchasing the outdoor kit.
  • It can be used in colder climates as it utilizes freeze protection.
  • 15-year warranty on the heat exchanger and 5 years on other replacement parts for residential installations.

Takagi tankless water heaters

Takagi is the third company from this list made by Japan.

Takagi offers two groups of tankless water heaters; non-condensing (T-KJr2, K4, D2, 110, 310, and 510) and condensing (H3M, H3J, H3S, H3, and 540P), heating domestic water in homes with up to 4.5 showers. Some models could be used in commercial applications.

Non-condensing models come with one standard-type heat exchanger and stainless steel venting, efficiency around 0.8, and low NOx emission.

Condensing models are high efficiency and ultra-low NOx models that come with high energy factors of over 0.9 and maximum water flow of 10 GPM, making them Energy Star compliant. All the models have an integrated temperature controller in indoor models and remote controllers supplied to outdoor units. They come with a 15-year warranty when used in residential applications or 5-year when used in a commercial.

The best models are equipped with high-quality elements such as the Air-Fuel Ratio (AFR) sensor that monitors and maintains proper gas combustion all the time, a primary commercial-grade heat exchanger, and secondary made of stainless steel.

Takagi T-H3

Takagi T-H3-DV tankless and condensing water heaterTakagi T-H3-DV

Features highlights:

  • Takagi T-H3 is equipped with the primary heat exchanger made of commercial-grade copper alloy and secondary made of stainless steel.
  • Bypass and flow adjustment valve for durable work with the optimal control in high-demanding applications.
  • Gas input in the range from 15,000 to 199,000 BTU.
  • Electric freezing protection system.
  • Complies with the Energy Star requirements.
  • Venting flexibility with the power vent or power direct vent options and indoor and outdoor installation.
  • High water flow rate up to 10 GPM.
  • Energy factor – 0.93.
  • Ultra-low NOx gas emission to protect the environment.
  • Cascading installation with an Easy-Link connecting up to 4 heaters or up to 20 heaters with a Multi-Unit Controller.
  • Takagi T-H3 comes with a warranty of 15 years on the heat exchanger in residential applications and 5 years on all parts.

So which one is better: Rinnai, Rheem, Noritz, Bosch, or Takagi?

As can be seen in this comparison, the benefits of any tankless water heater are vast. From continuous water heating and on-demand supply to high-efficiency operation and long-lasting service, tankless are built with customer satisfaction in mind. They can also save you money, time and nerves, due to the great diagnostic system.

Now when it comes to choosing the best tankless water heater, any model from above is a great option, while Rinnai, with the greatest selection, is our pick. That is why we recommend Rinnai RUR199 or similar RUR98, as you will get the most powerful and "greenest" unit, the highest energy efficiency with savings, and the ability to control its work using the smartphone.

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