Best Natural Gas Tankless Water Heater – Indoor & Outdoor Units

Natural gas tankless heaters are trending due to outstanding performance in cold climates at lower fuel cost. Also a best gas tankless water heater provides consistent temperatures along with a high volume of hot water, meanwhile energy consumption is low. 

Moreover, the liquid propane is also used to run tankless heaters and they are 22% more efficient as compared to conventional models.

Though the gas models are a bit expensive and their initial cost is high, think of the long run benefits, come with a gas tankless water heater.  It is really cool to know that you save almost $108 annually on electric bills. They last long ( more than 20 years if maintained properly).

In like manner, not only they are energy efficient, but eco friendly and do not pollute the environment as compared to their conventional counterparts. 

On the contrary, they are comparatively pricey as they require the proper installation of ventilation ports and fuel hookups. Moreover the availability of natural gas in your location is necessary for sure. 

There are a multitude models of natural gas tankless water heaters, and to choose the one compatible to your instant hot water demand is really a hard choice. Here, we come forward with tankless gas water heater review to make your decision best. 

Best Gas Tankless Water Heater

Our reviews about best tankless water heaters powered by gas are thoroughly researched and unbiased, helping you to buy the best tankless water heater gas for your family.

Top Rated Gas Tankless Water Heater – Honest Reviews

The following list of natural gas tankless water heater reviews shows these models are far superior and competent. Equipped with user friendly technology and economical prices would make your decision easier. 

Image Product Details   Price
Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater Rinnai RUC98iN Ultra Series Indoor Max GPM: 9.8
BTU: 199,000 max
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Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater Rheem RTGH-95DVLN 9.5 GPM Indoor Max GPM: 9.5
BTU: 199,900 max
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Takagi T-KJr2-IN-NG Indoor Tankless Water Heater Takagi T-KJr2-IN-NG Indoor Max GPM: 6.6
BTU: 140,000 max
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Rinnai V65IN Tankless Water Heater, Large, V65iN-Natural Gas Rinnai V65IN  Indoor Installation Max GPM: 6.5
BTU: 150,000 max
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BTU: 68,000 max
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Eccotemp i12-NG Tankless Water Heater Eccotemp i12-NG Tankless Water Heater Max GPM: 3
BTU: 80,000 max
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Rinnai RL94IN RRL94iN, 9.4 GPM, RL94iN-Natural Gas Rinnai RL94IN Natural Gas Max GPM: 9.4
BTU: 199,000 max
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Rheem RTG-84XLN-1 Tankless Water Heater Rheem RTG-84XLN Outdoor Max GPM: 8.4
BTU: 157, 000  max
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Rinnai V65EN RV65eN Rinnai V65eN Outdoor Installation Max GPM: 6.3
BTU: 120,000 max
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Rinnai RU199iN RRU199iN, RU199in-Natural Gas Rinnai RU199iN Indoor Installation Max GPM: 11
BTU: 199,000 max
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1. Rinnai RUC98iN Indoor Natural GasBest Instant Hot Water Heater Overall

 Rinnai RUC98iN Ultra Series Indoor Natural Gas, review tankless water heater gas
  • PVC venting option
  •  space-saving design
  • Up to 0.96 Energy Factor
  • Ultra low NOx emissions

Technical Specifications

Power Source‎Wind-Powered
Voltage ‎120 Volts
Item Weight 82 pounds
Product Dimensions ‎10 x 18.5 x 26 inches
Warranty Description Residential: Limited 12-year on heat exchanger, 5-year on parts, 1-year on labor (5-year optional on labor)

Commercial: Limited 5-year on heat exchanger
Included Components Water heater

Rinnai RUC98iN is an indoor gas tankless water heater with an electric ignition system. This heater consists of a digital display to monitor temperature and it could be regulated by a MC-91-2US controller. It also contains a temperature lock feature that restricts unauthorized use. The venting of this unit consists of concentric and twin pipe PVC. Being the best tankless gas water heater, Rinnai RUC98iN operates on natural gas which requires a maximum 199,000 BTU/H. It ultimately provides 96% efficiency rate with an energy factor of 0.92 EF.

two venting options: concentric & PVC venting

Due to its wide range of temperature starting from 98-140-degree Fahrenheit, it is perfect for domestic use and for commercial use temperature ranges from 98°F to 185°F.

Talking about its GPM which is 9.8, makes this unit the biggest tankless hot water heater. You can get hot water available at 4-5 faucets working simultaneously without reduced water flow. It consumes 64 Watts electric current. But in winters there should be at least 146 Watts electricity to prevent it from freezing. 

Hot Water On-Demand

Rinnai tankless water heater puts back hot water into circulation via pipes to provide hot water rapidly. Even if your home does not have a separate return line, Rinnai’s SE+ Series due to its ThermaCirc360 technology can operate without putting an additional line.

This unit provides a tremendous water flow rate of 9.8 Gallons per Minute. It provides a maximum pressure of 150 PSI and can be used at various channels at the same time.

Space Efficient

This compact unit allows you to utilize your space more efficiently – since it is only the size of a suitcase. One of the most significant features of the Rinnai tankless water heater is that it could be installed in unusual spaces like attic and closet. It also ensures an easy and unstrained installation process.


In case you face some technical issue related to any part you don’t need to buy a whole new unit because all spare parts of Rinnai Tankless water heater are available at extremely affordable prices.

Research revealed that Rinnai Tankless water heater helps to lower the electricity bills – since it works on natural gas ( which is a lot cheaper than electricity) and because you use it only when you need it.

Easy Installation and warranty

This heater is extremely easy to install and offers an amazing warranty of  12-year on heat exchanger, 5-year on parts, 1-year on labor for residential application 

And for commercial application: 5-year on heat exchanger, 5-year on parts, 1-year on labor.


  • Maximum energy is saved being high energy efficient model (96%)
  • Smart choice for both commercial and residential use
  • Eco friendly with low NOx emissions
  • 9.8 GPM sufficient for huge hot water demand
  • Noiseless operations
  • Discretionary venting method
  • Suitable for multiple fixtures and shower simultaneously


  • Rather an expensive model
  • Professional installation required which is a little costly
  • Electric panel upgradation required in case of old homes

2. Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent- Whole House Gas Tankless Water Heater

Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent, best natural gas tankless water heater
  • Low Nox Version
  • 94-Percent Energy efficient
  • condensing heat exchanger
  • Intelligent electronic controls

Technical Specifications

Power Source‎Gas Powered
Voltage ‎110 Volts
Item Weight ‎79 pounds
Product Dimensions ‎‎18.5 x 9.75 x 27.5 inches
Special Features  Guardian overheat film wrap (OFW), EZ-Link cable, Built-in electric blower, Two-pipe direct vent system designed for PVC pipe, Self-diagnostic system
Included Components Digital remote control and 10 ft. of thermostat wire included, Supplied with a 120-volt power cord (indoor models only)

Rheem RTGH-95DVLN comes with an amazing 9.5 GPM flow rate. The recirculating kit provides rapid hot water and saves up to 12,000 gallons water/year. It offers fast heat up  to approximately 8,400 ft height above sea level. Its smart electronic controllers help ensure safety and make it energy efficient. It works on natural gas which makes its usage very affordable.

Its amazing temperature lock feature with digital display protects it from any accidental working. Its freeze protection is up to -30°F.This impressive heater provides a great GPM rate which allows you to have hot water in 4 bathrooms at a time – which is enough for a relatively large family. It’s extremely low NOx emission makes it environmentally efficient and hazard free.

Budget Friendly

This unit provides efficiency at a very reasonable cost. It operates on natural gas providing 94% energy efficiency and is proved to significantly reduce your bills. It comes with the new stainless-steel heat exchangers condensers make this model the best on demand water heater.

stainless steel heat exchanger

Availability of Filtered Water to Multiple Faucets

This device ensures that your precious time is not wasted waiting for the hot water – hot water on demand gives huge savings. It has the capacity to serve multiple applications such as dishwasher, washing machine and baths simultaneously.


With its new feature including venting with band connections makes it even more convenient to install.

  • venting up to 150 ft  with 3″ PVC pipe
  • 60ft with 2″ PVC


This heater covers a 12-Year warranty on heat exchanger, 5-Year on parts and 1-Year on labor.


  • Recommended for larger households
  • Remote access through digital control
  • Monitor temperature through digital display
  • Equipped with freeze protection
  • Highly energy efficient
  • Direct vent system through twin pipe


  • A costly item
  • May require professional installation
  • Manual adjustment require at times

3. Takagi T-KJr2-IN-NG Natural Gas Gas Tankless Hot Water Heater

Takagi T-KJr2-IN-NG Natural Gas, best tankless water heater gas
  • 140,000 BTU
  • 6.6 GPM max flow rate
  • Energy factor of 0.81-0.83
  • Constant temperature monitoring

Technical Specifications

Power SourceBattery Powered
Voltage ‎120 Volts
Item Weight ‎37 pounds
Product Dimensions ‎‎
‎6.7 x 13.8 x 20.3 inches
Certification Energy Star
Warranty DescriptionThe heating exchanger with a 10-year warranty and parts with a 5-year warranty for residential application, commercial application 5/3 year respectively

This unit offers you an amazing 6.6 GPM flow rate which is a unique feature – if you compare it with other tankless heaters of similar category. The most amazing thing about this unit is that it is the smallest water heater in the world making it perfect for small apartments, huts and is capable enough to supply hot water to 2 bathrooms at a time.


Takagi T-KJr2-IN-NG has proven itself to be the most reliable indoor tankless water heaters. Output capability of this unit is almost equal to a 40-gallon tanked water heater.

Air fuel Ratio (AFR) sensor keeps a constant check on temperature fluctuation and prevents the system from emitting harmful gases such as NO and NO2.  To enjoy long years of comfort, you can rely on its durability.


It shows great competence as it does not require electricity. Natural gas is the sole fuel to make this unit operational, which results in saving a huge amount of money.

Takagi T-KJr2-IN-NG provides a maximum flow rate of 6.6 GPM but you can reduce it according to your need.

You can also change the temperature of hot water ranging from 120 to 167degrees depending upon your desire. This compact size unit will provide 83% efficiency which will definitely save your pocket from heavy bills.


Commercial grade copper is used in this heater which ensures much improved and smooth transfer of heat, minimizing the damage through corrosion. Therefore, they last for long and work optimally.


This heater comes with all the direction to install and operate which makes it extremely user friendly.


This product has 10-year heat exchanger warranty and 5-year warranty for the parts. Users can claim warranties only if the heater was installed according to the instructions provided and by a certified professional.


  • Abundant flow rate 6.6GPM
  • Sleek design and trouble free installation and maintenance
  • Consumes less fuel
  • Durable, strong and cost effective


  • Produces noise during operational switches
  • Warranty is effective if pro installation is done

4. Rinnai V65IN Tankless Water HeaterNatural Gas Indoor Water Heater

Rinnai V65IN Tankless Water Heater, best tankless hot water heater gas
  • Up to 6.5 GPM
  • Endless hot water
  • Save Valuable Space
  •  Mobile app features timers

Technical Specifications

Power Source
‎Gas Powered
Voltage ‎120 Volts
Item Weight ‎‎45.6 pounds
Product Dimensions ‎‎
‎‎17.5 x 30 x 13 inches
Special Features ‎Temperature Range with Controllers: 98°F – 140°F, Energy Factor of .82 for Both Gas Types, Pre-set at 120°F (adjustable to 140° by installer, Compatible with Full Line of Rinnai Digital Controllers
Warranty Description10-Year Warranty on Heat Exchanger, 5 Year Parts, 1 Year Labor

Owning to its compact design Rinnai V65IN is among the top choices for small houses and apartments. It is an indoor top rated tankless water heater in which the company incorporated latest technology that ensures  the heater consumes 40% less Energy as compared to conventional  gas heaters thus, reducing the bills.

Heat and Water Flow

The  gas consumption of the heater ranges between 10,300 – 150, 000 BTU. And it provides 6.5 GPM when there is a small temperature rise. Important to note that, with extreme cold inlet water temperature, this gas tankless water heater provides 3.3 GPM only.

Considering its compact design this flow rate can support two sinks, and one hot shower at a time without running out of hot water.


Due to the latest technology of copper Heater exchanger, it operates at maximum efficiency ultimately ending up causing a reduction in net energy use. Amongst many other features the heater has three Modes of operation that can be selected manually as per requirement

  • Standby mode = 02 Watt
  • Normal mode = 76 Watt
  • Anti Frost protection mode = 120 Watt

WI-FI Vonnectivity

The latest Wi-Fi technology incorporated in the heater, allows the user to have multi management features. Hence, providing full remote control of the unit from anywhere in the house.

Optional Control Smart wi-fi technology responds to voice commands for remote access-01

Easy Installation

According to the majority of the customer reviews, this tankless heater is extremely easy to install. However, you need to do some research before installing this unit by yourself.

But if you find it difficult you can always call the experts to install the heater.

Warranty Policy

  • The warranty of this product covers the following areas
  • 120 months warranty for Residential Heat Exchanger
  • 12 months warranty for  Residential Labor
  • 60 months warranty for Residential Parts


  • High energy efficient with a maximum flow rate of 6.5 GPM
  • Special features are integrated with mobile app like timer, schedule and vacation modes
  • Save valuable floor space
  • Leak identifier system is integrated
  • Smart decision for small homes and apartments
  • Low NOx emissions


  • Demand separate venting kit
  • Professional installation is recommended
  • Increased lag time

5. Camplux CM264-NG Natural Gas Residential Water Heater On Demand Gas Water Heater

Camplux CM264-NG Natural Gas Residential Water Heater, best tankless gas water heater
  • Flame-out protection
  • Eco and Full gas switch
  • Perfect for small homes
  • Digital temperature display


Technical Specifications

Power Source
‎‎Wind Powered, Fuel Powered
Voltage 120 Volts
Item Weight ‎‎45.6 pounds
Product Dimensions ‎‎
‎‎‎12.8 x 5.91 x 20.28 inches
Included Components‎CM264 Natural Gas Water heater, Instruction Manual, Horizontal Venting, Installation Hardware
Warranty Description1 Year Warranty

CM264-NG is an indoor tankless water heater which is extremely suitable for small houses, apartments and motor vehicles. This heater has a digital display from which you can easily control and monitor temperature.

CM264-NG tankless water heater has some other impressive features such as innovative combustion defense, protection from frost and inbuilt maintenance notifier.

Dry combustion feature and digital temperature control option makes it 88.5 % efficient. This water heater works on 0.4 PSI and provides a maximum output of 68,000 BTUs each hour.

The temperature increases up to 77- degree Fahrenheit at 2.64 GPM. This unit is specifically designed to save space and money at the same time. It is suitable for a maximum 2000 ft height. 

You can easily set the temperature according to your need with its special summer or winter options. This model does not require any heavy tools or machinery for installation because this is a ready to install heater with a powerful ventilation pipe.

Successful operation depends on natural gas and electricity of 20 KW . The moment the sensors observe water flow in the pipes the system itself starts working.

Extremely affordable

The tag price of this CM264-NG is nothing compared to the features it provides. Since it works on natural gas/propane, it helps you save a lot of money. You can utilize its WI-FI connectivity feature to start or stop according to the need – thus, saving  both time and money.

Energy saving

Although this heater is to be installed indoor, its venting pipe must be outside in order to safely discharge exhaust into the atmosphere. When the temperature reaches up to the desired demand (optimum temperature), the system stops automatically rather than wasting energy. Moreover, this unit features eco and full gas switch for energy saving and get ideal hot water temperature.

Eco & full switch options residential water heater

Easy Installation and warranty

It is easy to install indoors because of its compact size and offers a limited warranty of 1 year.


  • Generous flow rate
  • Accurate water pressure
  • No fluctuation in water temperature is noted
  • Compactness and light weight with easy installation
  • Saves energy and environment friendly
  • Advanced safety protection


  • Venting may create problem
  • Takes time to heat water

6. Eccotemp i12-NG Tankless Water HeaterBudget Friendly Tankless

 Eccotemp i12-NG Tankless Water Heater, best rated tankless gas water heater
  • LED display controls
  • Reduce energy consumption
  • Safe electronic ignition system
  • Automatic temperature controls

Technical Specifications

Power Source
‎‎‎Gas Powered
Voltage ‎‎‎120 Volts
Item Weight ‎‎‎28.8 pounds
Product Dimensions ‎‎
‎‎‎‎17 x 29 x 11 inches
Included Components‎Horizontal Vent Kit, I12-NG Tankless Water Heater, Instruction Manual, Installation Hardware
Warranty Description2 Year Limited Manufacturer Warranty

The Eccotemp i12-NG tankless water heater is an innovative and advanced model which makes it superior to any other heaters available on the market.

 It comes in a smooth black laminated safety glass, mechanized temperature monitoring option and a digital display touchscreen to control and observe temperature and water flow.

This unit is a ready to install and its 110/120-volt UL listed power wire regulates the ventilator inside it, LED screen and Product Control Board.  It works efficiently up to 5500ft.  It is a natural gas-based heater and is rated at 80,000 BTUs.

Flow Rate

This unit offers an impressive water flow rate of 3 GPM with a 35-40 degree rise in temperature. Whereas, at 1.5 GP the temperature increases up to 70- degree. It is suggested as a perfect choice for a small family of 2-3 members. It is also suitable for small apartments, cabins, motor houses and commercial use. Eccotemp i12-NG has the ability to deliver hot water to 2-3 multiple faucets at the same time.

Advanced Features

This unit is proved to be an extremely efficient and budget friendly heater. The advanced PCB (Product Control Board) and improved gas plugs ensures best performance and comfort without disturbing the customer’s wallet. You don’t need to worry about the safety and security being equipped with water movement sensors and child-lock features.


This heater is designed for indoor operation and is easy to install. But you might want to hire a professional because the manual is not always easy to understand.

Due to its small venting pipe, high heat output (80,000 BTU) and the need to install safety pressure release, it is recommended to ask an expert for installation.


If this unit is installed and operated according to the provided instructions then Eccotemp provides a 2 year limited warranty.


  • Integrated with LED display controls
  • Ignition mechanism is secure
  • Equipped with child safety lock
  • Stylish, compact and saves ample space
  • Energy efficient and maintains constant supply of hot water


  • Exhausting process may get hot
  • Installation is a bit tricky and pro installation is suggested

7. Rinnai RL94IN RL Series HE+ Tankless Hot Water Heater Top Rated Tankless Gas Hot Water Heater

Rinnai RL94IN RL Series HE+ Tankless Hot Water Heater, best rated tankless water heater gas
  • Endless hot water
  • Sustainable reliability
  • Affordable, efficient savings
  • Sleek design fits anywhere

Technical Specifications

Power Source
‎‎‎Gas Powered
Voltage ‎‎‎120 Volts
Item Weight ‎44.2 pounds
Product Dimensions ‎‎17.5 x 13 x 31 inches
Included Components‎Valve Kit
Warranty Description10 year warranty on the heat exchanger and 5 years on the circuitry, electronics, and igniter

Rinnai RL94IN is the best natural gas tankless water heater equipped with state of art technology that is suitable for both Indoor and outdoor facilities. It provides a sound efficient environment so that one can just install it and forget after that. It will provide you  continuous hot water in an effective and efficient manner.


It requires a minimum of 10,300 BTUs  and a maximum of 199, 000 BTUs and operates between 98-degree Fahrenheit to 140-degree Fahrenheit- making it a thermal efficient unit.

Water flow

This heater is considered a workhorse since the heater works very quietly and smoothly. Also, Rinnai RL94IN tankless heater provides hot water to approximately five faucets simultaneously and there is no shortage of water at all.

This unit operates with an impressive GPM of 9.4 making it possible to wash dishes, do laundry and even take bath at the same time.

supports up to 5 appliances

Easy to install

This heater is very easy to install and operate. You can do the installation by yourself by following the directions provided on the handbook.

Also, you don’t need to have heavy tools or machinery to install this unit.

Re circulation

The standout feature of this heater is that it provides the recirculating facility which helps the owner in receiving water instantly without wasting any time and water.

Wi-Fi system

Having a built in Wi-Fi system makes it even more effective for the operator to control this heater from any part of the house and at any time.


  • Rinnai RL94IN comes with a long warranty for its parts and labor.
  •  Residential Heat Exchanger – warranty for 144 months
  •  Residential Labor – warranty of 12 months
  •  Residential Parts – warranty of 60 months


  • Amazing flow rate 9.4 GPM for larger households
  • Intelligent temperature setting for both commercial and residential use
  • Excellent flow rate in economical pricing.
  • Smart sensors detect and stop mineral deposits
  • Can be converted to propane any time
  • Outstanding and optimal performance


  • Price is high
  • Weighty model and installation is a little tough

8. Rheem RTG-84XLN Tankless Water Heater – Most Efficient Tankless Water Heater

Rheem RTG-84XLN Tankless Water Heater, best tankless water heater natural gas
  • Freeze protection 
  • Recirculation pump
  • Minimizes cold water burst
  • Exclusive savings technology

Technical Specifications

Power Source
Voltage ‎‎‎120 Volts
Item Weight ‎57 pounds
Product Dimensions ‎‎‎8.88 x 13.88 x 23.63 inches
Included Components‎‎Control Board, Inlet Thermistor, Heat Exchange Thermistor, Outlet Thermistor, Thermistor Wiring Harness, Gas Control Valve, Gas Control Wiring Harness, Burner Assembly, Igniter Coil, Ignitor Rod, Blower Motor, Blower Case, Burner Manifold, Flame Rod, Flame Rod Wire, Gas Inlet Connector, Water Control Valve, Bypass Assembly, Water Inlet Connector, Inlet Water Filter, Hot Water Outlet Connector, Drain Plug with Relief, Remote Control Terminal Block, Remote Control Terminal, Gas Shutoff Valve, Replacement Screw Kit, Replacement O-Ring Kit
Warranty Description 12years heat exchanger, 5 years parts and 1 years labor

This tankless water heater comes with an incredibly efficient flow rate of 8.4 GPM which can serve 3 bathrooms at the same time – enough for a family of 4-5 members. Also, you don’t need to leave your comfy bed anymore to switch on the heater because it can be controlled with smartphone connection as well as with the digital controller. There are many other impressive features of this heater such as low NOx – environment friendly; built in feature which sends automatic maintenance alerts; 83% efficient with  0.83 EF.

Plus, this biggest tankless hot water heater is designed with such material and in such a manner that it could survive up to -30 degrees without any change in hot water flow. It is renowned as one of the most robust heaters in the market. It consumes 157, 000 BTU of natural gas and provides uninterrupted water output.


Rheem RTG-84XLN provides hot water in seconds after starting the unit so that you don’t have to wait too long. Usually tankless heaters take some time to give hot water input due to their low activation degree. 

However, this tankless water heater with the support of efficient GPM provides rapid and continuous supply of water.  Therefore, it is not wrong to call this uit the best tankless hot water heater gas fueled. 


The best feature of the Rheem RTG-84XLN is that you can control and manage the temperature and water flow with the help of a digital display. Rheem RTG-84XL tankless heater comes with a re-circulation flow kit that makes it efficient up to 100%, so that you can use hot water the time you open the tap. It ensures safety and protection against over heating.

provides protection against over heating


This unit is to be installed outdoor which consequently helps you to save a lot of space inside the house.


Rheem offers users’ friendly warranties. Similarly, the RTG-84XLN has an impressive 5-years parts warranty, 1-year labor warranty and 12-years heat exchange warranty.


  • Uninterrupted supply of hot water on demand
  • Energy efficient and helps reducing utility bills
  • Ultra low NOx make model environment friendly
  • Heat is controlled through the digital regulator
  • Allows simultaneous use of multiple fixtures
  • No wait for hot water


  • Optimal performance in warm climate only
  • Professional installation is required
  • Regular and proper maintenance is required

9. Rinnai V65eN Instant Hot Water Heater Gas

Rinnai V65eN Tankless Hot Water Heater, best outdoor gas tankless water heater
  • Optional Wi-Fi Module
  • Max Energy Factor 0.82
  • Lightweight and Compact
  • Integrated Error Code Indicator

Technical Specifications

Power Source
Voltage ‎‎‎120 Volts
Item Weight ‎47.4 pounds
Product Dimensions ‎17.5 x 30 x 13 inches
Special Features‎‎Temperature Range with Controllers: 98°F – 140°F, Energy Factor of .82 for Both Gas Types, Pre-set at 120°F (adjustable to 140° by installer, Compatible with Full Line of Rinnai Digital Controllers,
Warranty Description10-Year Warranty on Heat Exchanger, 5 Year Parts, 1 Year Labor,

Rinnai V65eN is an ideal tankless water heater for small to medium residential spaces and is qualified to be operated in trailer houses as well. Being the best tankless water heater powered by gas requires a maximum input of 150,000 BTUs and can be ignited with a 0.4 GPM flow rate initially.

Due to its incredible hot water flow rate (6 gpm tankless water heater); Rinnai V65eN is sufficient enough to serve 2 or more bathrooms at the same time. It requires 57 Watts of electricity on operation mode, standby mode requires 2 Watts and 104 Watts to prevent its parts from freezing.

It is designed to work on extended temperature range i.e. from 98 degrees Fahrenheit up to 140 degrees Fahrenheit. Though this is not energy star qualified but uniform energy factor is 0.79.

This unit is capable of connecting with WI-FI and you can easily control and monitor this heater with a Rinnai digital remote controller. You can have a safe and secure experience with its special temperature lock feature that prevents unauthorized access.

Stress Free Installation

It is a compact and easy to install heater. You can easily install this heater with the help of the steps provided on the customer guidebook. Also, no heavy tools or expert plumbers are required to install it which is pretty amazing.

Being an outdoor installation, no need for specific venting as it direst vents to the outside.

Budget Friendly

This unit guarantees efficiency and reliability at a very reasonable cost. It operates on natural gas providing 85% efficiency output and is proved significantly to reduce your electricity bills. It has longer lifespan than traditional tank heaters.


Rinnai tankless water heater last up to twice as long as standard tanks
  • This unit has 120 months warranty for residential heat exchanger
  • 12 months warranty for residential labor 
  • 60 months warranty for its residential parts


  • Maximum 6.5 GPM ideal for average size households
  • Can be easily modified though default version require 120V
  • Ensures uninterrupted supply of hot water when needed
  • Meets the standard rules and regulation
  • Smart design and wall mounted helps saving space


  • May uses more amps than standard 120v
  • Low water pressure
  • Repairing may be costly

10. Rinnai RU199iN Sensei High Efficiency Tankless Water Heater

Rinnai RU199iN Sensei Super High Efficiency, best indoor gas tankless water heater
  • SE+ Super High Efficiency
  • Up to 11 GPM
  • Circ-Logic technology
  • Hot water on demand

Technical Specifications

Power Source
Voltage ‎‎‎120 Volts
Item Weight ‎74.1 pounds
Product Dimensions ‎22.05 x 14.76 x 33.86 inches
Special Features‎Water Heater
Installation Method
‎Wall Mounted, Natural Gas, Indoor Installation

Rinnai is wildly popular to manufacture tankless models powered by gas and this RU199 is no different. RU199iN is a high efficiency tankless water heater with a very low consumption of energy that saves you a lot of money. Direct Electronic Ignition system makes it even more prominent.

 You can easily operate this heater with the help of an Integrated Controller or you can also go for optional controllers such as: MC-195T-US, MC-100V-1US, BC-100V-1US, MCC-91-2US. It has a wide range of temperatures which ranges from 98° F to 140° F.

Its feature of meter adjustment makes it perfect for both household and commercial use. Just like other Rinnai Sensei heaters, this one is also WI-FI compatible and provides easy access to set temperature and hot water output rate.

The Rinnai RU199iN provides a remarkable water flow rate of 11 GPM which makes it a whole home tankless water heater. This unit runs on natural gas as well as on propane gas which are certified and environment friendly gas types. It has an energy factor of 0.96 EF – which makes it extremely efficient.

The availability of Wi-Fi connecting features makes it even more easy to use. This device offers fast heat up for up to 10,200ft. It is a very compact and space saving heater so you don’t need to create extra space in your home- since it fits almost anywhere. It is a mobile home certified heater with ultra-low NOx emission- to create an eco-friendly atmosphere.

Energy Efficient

Since this water heater works only on your demand so it ends up saving a lot of energy. Also, it comes with a fiber web in the burner to ensure equal and uniform flow of heat without wasting energy. It requires 15,000 BTU to 199,000 BTU to regulate properly.

Availability of water to multiple faucets

Rinnai RU199iN series ensures that you don’t waste time waiting for the hot water – hot water on demand is expected to provide a big savings. It is a perfect choice for a family of 4-5 people (3 bathrooms, dishwasher and washing machine).

Unstrained Installation

 This unit is ready to install – since it comes with everything you need.

Pressure Relief Valve and Isolation Valves included with this unit


  • Warranty only applies on Residential application
  • Heat Exchanger – 180 months
  • Residential Labor-  12 months
  • Residential Parts – 60 months


  • Energy efficiency is remarkable
  • Consumes less energy and increase saving
  • Certified heater with ultra-low NOx emission
  • No long wait for hot water
  • Eco friendly, durable with lifetime warranty.


  • Is expensive model as compared to other gas heaters
  • Professional installation is recommended which is costly too

Venting System For Gas Tankless Heaters

To enhance the efficiency and functionality of natural gas tankless models, proper venting for tankless heaters is crucial.

On the contrary, the electric tankless heater models do not require venting but proper electric system to run the tankless heater properly.

Generally, the natural gas tankless units ventilates in two ways. They are:

  • Direct Vent
  • Power Vent
gas tankless water heater venting method
Gas Tankless Water Heaters Venting Methods – Infographics


What is a gas tankless water heater?

It is one of types of tankless water heaters providing instant hot water on demand powered by natural gas. Natural gas is used to make them functional, so there is less consumption of energy and saving on electric bills ultimately. 

Despite their costly initial installation, they provide long run benefits as natural gas is cheap. Gas tankless hot water heater delivers instant hot water when you need it without running out of hot water. 

How does a gas tankless water heater work?

Tankless gas water heater does not store water like their traditional counterparts do. They heat the water instantly and deliver quickly. 

When any water application turns on, the inbuilt sensor detects the flow, and the natural gas heats up the heat exchanger which further heats the water. 

Surprisingly, the whole process completes in less than 10 seconds. A best tankless gas water heater ensures unlimited delivery of instant hot water.

What is the best gas tankless water heater on the market?

The superb gas tankless water heater has many outstanding features. Their optimal performance depends on their capacity, energy efficiency, energy star certification, output water flow, and  price.


Natural gas tankless heaters have maximum water flow ranges from 6 to 11 GPM. for bigger households, 10 gpm tankless water heater to 11 GPM heaters with 180,000-199,000 BTU are sufficient.

For medium households, 6 to 7 GPM flow rate is more than enough, allowing multiple water applications simultaneously to be run.

Energy Efficiency

The average energy factor rating or EF lies between 0.8 to 0.9. More simple way to understand this calculation is, 80 to 90% use of natural gas with 10 to 20% energy loss in order to heat up the water. 


Apparently, the gas tankless water heaters look expensive due to their high prices. But at a broader level, this $1000 dollar would prove to be a 20 year investment after all. 

Rinaai, Rheem, Takagi, Eccotemp and Camplus are some popular brands manufacturing high quality instant hot water heaters gas fueled.

Daniel Adley is a seasoned and skilled plumber with over 20 years of experience. Specializing in repairing and optimizing water appliances for large buildings, offices, and homes, he has a keen eye for efficiently identifying plumbing and maintenance issues. With a passion for his craft, Daniel brings extensive knowledge and expertise to every project, ensuring reliable and effective solutions for his clients.

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