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

Tankless water heater - Rinnai RUR199Tankless water heater

In recent years, tankless water heaters have gained popularity due to their energy efficiency, space-saving design, and on-demand hot water supply. However, with so many options available in the market, it can be challenging to determine the best fit for your home.

In this article, we will compare tankless water heaters to find the best models, taking into account factors such as performance, efficiency, features, and price.

Our comprehensive review covers several popular brands and models designed for point-of-use and whole-house water heating in residential applications.

We analyze the top manufacturers of tankless water heaters, including Bosch, Rheem, Rinnai, Noritz, and Takagi, and compare their benefits and main features. We also provide specific details on each model to help you make an informed decision and find the right one for your home.

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Compare tankless water heaters: Things to consider

While reviewing and comparing tankless water heaters, we found several standard features and benefits:

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

Rinnai tankless water heaters

When you compare tankless water heaters, Rinnai is one of the top manufacturers to consider, offering a wide range of models for both residential and commercial use. The company's product line includes both simple on-demand and condensing technology options.

Among the Rinnai tankless water heaters, the V (HE series) and RL models (HE+ series) are economy and non-condensing models that are suitable for small to medium-sized homes with moderate hot water demand. These models have a higher energy factor than tank-type models, ranging from 0.79 to 0.82, but they are not Energy Star certified.

The V series is the most basic model, lacking voice activation capability, an isolation valve for easy service, and Circ-logic option for fast hot water delivery found in the RL series. Both the V and RL series use one heat exchanger, an integrated temperature controller, and offer flexible venting options. These models are available in natural gas and propane options.

On the other hand, the RUCS and RUS models (SE series) are from the condensing group, offering higher efficiency of almost 0.9, making them Energy Star compliant. However, like the V series, these models do not have voice control, an isolation valve, or Circ-logic option. They also have a small temperature display.

The most advanced models are from the RUC, RU, and RUR series, which include all the features that Rinnai offers. These models are ultra-efficient, with an energy factor of over 0.9, making them Energy Star approved. The RUR series also features unique ThermCirc360 technology, allowing for recirculation with or without a dedicated line.

All Rinnai tankless water heaters offer Wi-Fi options for remote control and monitoring, adding convenience to your daily life.

Rinnai RUR199i

Rinnai RUR199iRinnai RUR199i

Rinnai RUR199i and RUR199e are the most robust tankless water heaters in their lineup, designed to deliver hot water to multiple fixtures simultaneously, making them ideal for large households or commercial applications.

The RUR199i is an indoor model, while the RUR199e is intended for outdoor use. With a high flow rate and advanced technology, these models can efficiently provide hot water to up to six different fixtures at the same time, ensuring everyone in the house has access to hot water whenever they need it.

Features highlights:

  • ThermCirc360 technology: Built-in recirculation pump, timer, and thermal bypass valve provide almost instantaneous hot water at the tap, reducing water waste and wait times.
  • Rinnai Circ-Logic technology: Set custom recirculation patterns that match your hot water usage, eliminating unnecessary waiting and providing hot water right when you need it.
  • Ultra-low NOx gas emission: Complies with strict emissions standards while delivering reliable, efficient hot water.
  • High water flow: With up to 11 gallons per minute, the RUR199 models provide ample hot water for up to six simultaneous fixtures, ensuring a reliable delivery to any home size.
  • Alexa voice integration: Enjoy the convenience of voice activation through Alexa, making it easy to operate and adjust the temperature without leaving your seat.
  • Wi-Fi monitoring: Remote access to maintenance and diagnostics via a smartphone, ensuring peace of mind and hassle-free maintenance.
  • Energy Star compliant: The RUR199 has an impressive energy factor of 0.96, which means significant savings on your energy bill.
  • Modulating gas valve: Rinnai's innovative modulating gas valve allows for power modulation from 15,000 to 199,000 BTU, providing precise and efficient temperature control.
  • Maximum vent length: You can install the RUR199 up to 150 feet away from the vent using either a concentric or twin pipe setup.
  • High altitude options: Suitable for installations up to 10,200 feet, making it ideal for high-altitude locations.
  • Certified for mobile home installation: The RUR199 is certified for use in mobile homes, providing flexibility and convenience.
  • Commercial-grade heat exchanger: Rinnai's heat exchanger is designed to withstand the rigors of commercial use, ensuring durability and long-lasting performance.
  • Integrated digital controller: The RUR199 comes with an integrated digital controller that displays error codes and provides easy-to-use temperature controls.
  • Integrated condensate collector: The indoor RUR199 features an integrated condensate collector that ensures efficient operation and easy maintenance.
  • Available models: The RUR199 is available in both indoor and outdoor versions and can be powered by natural gas or propane.
  • Warranty: Rinnai offers a 15-year warranty on the heat exchanger and a 5-year warranty on other components, providing peace of mind and protection for your investment.

Rheem tankless water heaters

If you want to compare tankless water heaters, it's worth considering the Rheem brand for its high-quality and energy-efficient products.

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

The condensing models are further divided into three sub-groups: Professional Prestige, Performance Prestige, and Performance Platinum. Customers can choose from a range of tankless water heaters that produce hot water with a flow rate of 8.4 to 11 gallons per minute (GPM), an efficiency of over 90%, and a power ranging from 157,000 to 199,000 British Thermal Units (BTU).

The appropriate model size depends on how many applications you need to use simultaneously. Regardless of the model you choose, rest assured that you will get the most advanced features and cutting-edge technology, providing you with the highest efficiency and savings.

Regarding the Mid-Efficiency series, there are two groups: Tankless Mid-Efficiency and Performance Mid-Efficiency, each offering three different sizes. The water flow ranges from 7.0 GPM to 9.5 GPM, with maximum power from 160,000 to 199,900 BTU.

The maximum Energy Factor for the Rheem Mid-Efficiency tankless water heaters is 0.82, which is lower than the condensing models, but still provides substantial savings when compared to tank-type heaters. The primary difference between the condensing and mid-efficiency models is that the former has two heat exchangers, while the latter has only one.

Rheem Professional Prestige 11.0 GPM - RTGH-RH11DVLN


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

Features highlights:

  • Eco-friendly gas burner with ultra-low NOx gas emission: The Rheem RTGH-RH11DVLN models have an ultra-low NOx gas burner, which means they emit fewer harmful pollutants into the atmosphere compared to traditional gas water heaters.
  • Dual stainless steel heat exchangers: These models have two stainless steel heat exchangers, which provide greater heat transfer and durability.
  • Built-in recirculation system: The built-in recirculation system helps reduce the wait time for hot water, making it almost instant.
  • Gas input is in the range from 18,000 to 199,000 BTU: This range of gas input provides versatility in heating the water to the desired temperature.
  • High water flow: The Rheem RTGH-RH11DVLN models have a maximum water flow rate of 11 gallons per minute, making them ideal for high demanding applications such as large households or commercial properties.
  • The unit allows programmable time-based activation: This feature allows you to set the unit to activate at specific times, ensuring hot water is ready when you need it.
  • Excellent performance up to 8,400 ft. elevation: The Rheem RTGH-RH11DVLN models can operate efficiently at elevations of up to 8,400 feet, making them suitable for use in high-altitude areas.
  • Smart: The unit is compatible with EcoNet for smart home management, including leak detection, gas, and water usage reports including maintenance reminders. This feature allows you to integrate the unit with EcoNet, a smart home management system, enabling you to monitor water and gas usage, detect leaks, and receive maintenance reminders.
  • Wireless remote: The Rheem RTGH-RH11DVLN models come with a wireless remote that allows you to adjust the temperature of the hot water from anywhere in the house.
  • Intelligent electronic system and self-diagnostic program: These models have an intelligent electronic system that can diagnose and troubleshoot any issues that may arise.
  • Long vents: The Rheem RTGH-RH11DVLN models have a maximum vent length of up to 100 feet using PVC, providing greater flexibility in installation.
  • Compatible with the ½” gas line: These models are compatible with a ½” gas line, which is a common gas line size found in most households.
  • Decent warranty: Rheem offers a 12-year warranty on the heat exchanger and a 5-year warranty on other replacement parts for residential installations, providing customers with peace of mind.

Noritz tankless water heaters

The Japanese company Noritz provides a range of tankless water heaters that are designed to meet the needs of different customers and home sizes.

Noritz is known for its innovative and reliable products, and should definitely be considered when you want to compare tankless water heaters and find the best one.

The Noritz NR series is recommended for homes with moderate usage or up to 3.5 baths. These mid-efficient models have a power output of up to 199,900 BTU and can provide a maximum water flow rate of 9.8 GPM. Their energy factor is around 0.81, and they use only one heat exchanger.

The Noritz EZ series is ideal for replacing tank-type water heaters of 40, 50, and 75 gallons, as well as retrofitting existing water heating systems. These models have top-mounted connections, which makes the transition easier, faster, and more cost-effective. EZ models feature two stainless steel heat exchangers and use condensing technology.

NRCB combination boilers are designed for homeowners who want to heat both space and domestic water simultaneously. All the models in this series are condensing, ensuring high-efficiency water heating that doesn't pollute the environment like standard models.

The Noritz NRCP line of tankless water heaters is the most advanced and energy-efficient. These condensing models use an internal pump for water recirculation, which ensures faster hot water delivery. Like the other models, they are Energy Star certified and can provide hot water in large volumes.

Noritz NRCP1112

Noritz NRCP1112 tankless water heaterNoritz NRCP1112

The Noritz NRCP1112 is a residential condensing and tankless water heater equipped with a built-in recirculation pump with two modes - with and without the return line. This feature ensures a shorter delivery time for hot water, providing a better user experience.

Features highlights:

  • With its powerful gas burner capable of generating up to 199,000 BTU and dual heat exchangers, the Noritz NRCP1112 model is an ideal condensing and tankless water heater for larger homes or households with up to 4.5 baths. It offers an exceptional energy factor of 0.94 and a water flow rate of up to 11.1 GPM, providing a constant supply of hot water and high efficiency for your daily needs.
  • Energy Star compliance and ultra-low NOx gas emission make the Noritz NRCP1112 an eco-friendly and environmentally conscious choice for your home's hot water needs. You can enjoy the comfort and convenience of hot water without compromising your commitment to reducing your carbon footprint.
  • The dual heat exchanger design of the NRCP1112 ensures superior heat transfer and efficiency, which translates into cost savings on your energy bill. With an energy factor of 0.94, this model is one of the most efficient options on the market today.
  • You can adjust the water flow rate of the NRCP1112 according to your household's needs, with a range of 0.5 to 11.1 GPM. The modulating power range of 18,000 to 199,000 BTU ensures that you get the exact amount of hot water you need when you need it, saving you both time and money in the long run.
  • The built-in temperature controller of the NRCP1112 allows you to set the temperature of your hot water between 100 and 140 F, providing you with a customizable and comfortable hot water experience.
  • Safety features of the NRCP1112 include a flame sensor, overheat cut-off limit, gas leak detector sensor, water leak detector sensor, exhaust temperature sensor, and water temperature sensor, ensuring that you and your family are protected from any potential safety hazards.
  • The NRCP1112 is also recirculation compatible, making it easy to integrate with your existing plumbing and heating systems.
  • The self-diagnostic onboard computer system of the NRCP1112 ensures that any issues with your hot water system can be identified and resolved quickly and efficiently, minimizing downtime and inconvenience for you and your family.
  • Noritz backs the NRCP1112 with an industry-leading 12-year warranty on the heat exchanger and 5 years on other replacement parts for residential installations.

Bosch tankless water heaters

When you compare tankless water heaters, it's important to include Bosch in your research as the brand offers a range of efficient and durable models suitable for various household sizes and needs.

The Bosch Group is a reputable German manufacturer of Bosch tankless water heaters for residential and commercial use. With several models available, consumers can choose from non-condensing and condensing models grouped in the Therm and Greentherm series.

The Greentherm 9000 series is the newest line of seven condensing and tankless water heaters. They come with state-of-the-art engineering, superior energy efficiency, exceptional performance, and long life. These models are a great choice for those who value sustainability and eco-friendliness.

The Therm series includes several models to meet different needs. For instance, the Therm C 1210 ES is the condensing model that offers the power of up to 225,000 BTU, a high water flow of 12.1 GPM, and an efficiency of up to 98%. This model is perfect for high-demanding homes. Also, Intelligent Cascading allows combining up to 24 units into one system, making it an excellent option for large commercial applications.

Therm 940 ES and 830 ES are two of the smallest and non-condensing models from the Therm series. Despite their size, they offer the maximum efficiency of 83%, resulting in savings of up to 50% on utility bills. Both models are suitable for residential and commercial applications and can easily fit into small spaces.

Bosch Greentherm 9000 series

Bosch 9000 tankless water heaterBosch 9000

The Bosch Greentherm T9900I (SE 199) is the most powerful residential tankless water heater from this manufacturer, offering a maximum power of 199,000 BTU and a water flow rate of up to 9.8 gallons per minute. Despite its high performance, it is compact and lightweight, making it easy to install in a variety of spaces. The unit also features advanced condensing technology, which ensures ultra-high efficiency and lower energy bills for homeowners.

Features highlights:

  • Tankless and condensing technology: Tankless water heaters heat the water as it flows through the unit, rather than storing hot water in a tank. Condensing technology allows the unit to extract heat from the exhaust gases, making it more efficient.
  • Ultra-high energy factor of 0.96: The energy factor (EF) is a measure of a water heater's efficiency, and a higher number means greater efficiency. An EF of 0.96 is very high and indicates that this unit can convert 96% of its energy input into hot water output.
  • High water flow of 11.2 GPM: GPM stands for gallons per minute, and this unit can provide up to 11.2 gallons of hot water per minute, making it suitable for larger households with high hot water demand.
  • Two heat exchangers; secondary made of stainless steel: Heat exchangers transfer heat from the burner to the water. The secondary heat exchanger in this unit is made of stainless steel, which is durable and resistant to corrosion.
  • Ultra-low NOx gas emission: NOx (nitrogen oxides) are pollutants that can harm the environment and human health. This unit has very low NOx emissions, making it an environmentally friendly choice.
  • Built-in recirculation pump: A recirculation pump can keep hot water ready to use at all times, reducing the wait time for hot water at the tap.
  • Built-in touch screen to adjust the temperature and for diagnostics: The touch screen makes it easy to adjust the temperature and diagnose any issues with the unit.
  • Top connections and integrated drain ports: The unit is designed for easy installation and maintenance, with top connections and integrated drain ports.
  • Integrated Wi-Fi: You can remotely control the temperature, set the system into the recirculation mode and monitor usage and other parameters: The unit can be controlled remotely using a mobile phone, allowing you to adjust the temperature and monitor usage and other parameters.
  • Integrated sensor technology: The unit has integrated sensor technology that helps to optimize its performance.
  • Modulating gas valve: A modulating gas valve can adjust the gas flow to the burner, ensuring efficient combustion and optimal performance.
  • Energy Star compliant: The Energy Star program is a voluntary program that promotes energy-efficient products. This unit meets Energy Star standards for efficiency.
  • High turndown ratio of 22:1: Turndown ratio is a measure of a unit's ability to modulate its output. A high turndown ratio means that the unit can adjust its output to match the hot water demand, improving efficiency and reducing energy waste.
  • Indoor and outdoor use: This unit can be installed both indoors and outdoors without the need for an additional outdoor kit.
  • Freeze protection: Freeze protection ensures that the unit can operate in cold weather without freezing and damaging its components.
  • Long warranty: This unit comes with a long warranty period of 15 years on the heat exchanger and 5 years on other replacement parts for residential installations.

Takagi tankless water heaters

Takagi is another company Japanese company that offers two groups of tankless water heaters: non-condensing and condensing models.

The non-condensing models (T-KJr2, K4, D2, 110, 310, and 510) are designed to heat domestic water in homes with up to 4.5 showers. Some models are also suitable for commercial use. These models have one standard-type heat exchanger, stainless steel venting, an efficiency of around 0.8, and low NOx emissions.

The condensing models (H3M, H3J, H3S, H3, and 540P) are high-efficiency and ultra-low NOx models. They have high energy factors of over 0.9 and a maximum water flow of 10 GPM, making them Energy Star compliant. All models have an integrated temperature controller for indoor models and remote controllers for outdoor units. These models come with a 15-year warranty for residential use or a 5-year warranty for commercial use.

The best Takagi models are equipped with high-quality elements such as an Air-Fuel Ratio (AFR) sensor that monitors and maintains proper gas combustion all the time, a primary commercial-grade heat exchanger, and a secondary heat exchanger 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 a tankless water heater that boasts a primary heat exchanger made of commercial-grade copper alloy and a secondary heat exchanger made of stainless steel. This combination of materials ensures maximum durability and longevity.
  • In addition to its durable construction, the T-H3 features a bypass and flow adjustment valve, which allows for optimal control in high-demanding applications. This feature ensures that the unit performs consistently, even when demand is high.
  • The T-H3 has a gas input range of 15,000 to 199,000 BTU, making it suitable for a wide range of residential and commercial applications.
  • One of the most notable features of the T-H3 is its electric freezing protection system. This feature helps to prevent damage to the unit and ensures that it continues to function even in extreme temperatures.
  • The T-H3 is also Energy Star compliant, which means that it meets strict energy efficiency guidelines set by the U.S. Environmental Protection Agency. This ensures that the unit operates efficiently and minimizes energy waste.
  • With its power vent or power direct vent options, the T-H3 offers great venting flexibility, making it suitable for both indoor and outdoor installation. This feature allows for easy installation and ensures maximum convenience.
  • The T-H3 is capable of delivering high water flow rates of up to 10 GPM, which is ideal for larger households or commercial applications.
  • The T-H3 boasts an impressive energy factor of 0.93, which means that it operates with maximum efficiency and minimizes energy waste.
  • In addition to its impressive energy efficiency, the T-H3 also boasts ultra-low NOx gas emissions, which helps to protect the environment by reducing air pollution.
  • The T-H3 is capable of cascading installation with an Easy-Link that connects up to 4 heaters or up to 20 heaters with a Multi-Unit Controller. This feature allows for easy installation and customization to meet specific requirements.
  • Takagi T-H3 comes with a warranty of 15 years on the heat exchanger in residential applications and 5 years on all parts. This ensures that customers can enjoy peace of mind and worry-free operation of their unit for many years to come.

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

In this article where we compare tankless water heaters, it's evident that the benefits of using these units are numerous. They offer continuous water heating, on-demand supply, high-efficiency operation, and long-lasting service, all designed to ensure customer satisfaction. Additionally, the advanced diagnostic systems of tankless water heaters can save you money, time, and stress by quickly identifying and addressing any issues.

When it comes to comparing tankless water heaters and selecting the best one, any model from the list above would be a great choice.

However, based on the wide selection and impressive features, we recommend Rinnai as the top pick. Specifically, we suggest the Rinnai RUR199 or the similar RUR98, which offer the most power and efficiency, significant savings, and the ability to control the unit with your smartphone. By choosing Rinnai, you can rest assured that you are getting a top-quality product that will meet your water heating needs and exceed your expectations.

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