10 Best Tankless Gas Water Heater – (Top Rated Reviews of 2020)

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Written by Eric

Last Updated: 12/09/2020

Warm water in bathroom

Tankless gas water heaters are one of the most efficient water heaters that can be installed practically anywhere if you have the right unit. They work only when the faucet is turned on so that the hot water does not damage the pipes and does not waste energy. They are energy efficient and save about 30% to 50% energy than regular tank heaters. The work of these heaters is according to their size, the space they use, the amount of use, and the features that they have. You can find indoor ones or outdoor ones according to your preferences.

My guide will help you find the best tankless gas water heaters to help make a smarter decision. This guide will answer frequently asked questions and focus on some important factors to base your decision on. You can read my gas tankless water heater reviews here below to find the best in the market.

1. The Winner - Best Overall

Rinnai V65iN High Efficiency Tankless Hot Water Heater, 6.5 GPM - Natural Gas

Rinnai V65IN

  • High Efficient
  • Natural Gas
  • Compact Space Saving Design
  • Indoor Heater

Instead of settling for an indoor, bulky water heater that takes up a lot of space, you can simply choose the Rinnai Tankless water heater series. It’s small and compact but it gives off a great heat tendency of about 150,000 BTU. The No Nox series makes it much safer and efficient to be indoors. One of the best features that make this very safe is that if there is a home leak detection, the unit shuts off to prevent any further damage that it may be able to cause.

This system is perfect for mobile and small houses. It can run on natural gas or propane as per the preference of the users. The water flow is at a rate of about 6.6 GPM with energy star certification to make sure it is safe and energy efficient. You can also have a separate bathroom controller with this water heater to make it more versatile.

2. The Runner Up

Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater


  • Energy Efficient
  • Condesing Heat Exchanger
  • Natural Gas

Some gas water heaters consume a lot of energy but if you are looking for an option that will help reduce the energy consumption, then this Rheem tankless water heater is the perfect option for you. It consumes 94% less energy than most gas heaters. The system has a stainless-steel condensing heat exchanger that helps in making it more effective. The electronic controls are one of the reasons why energy is saved and makes the machine safe for indoor usage. The machine has a digital display system that makes it easy to read the water temperature.

The vent system in this water heater is a direct system that is compatible with PVC pipes. The heater can also work at high altitudes making it most efficient for apartments on the higher levels. Users will find it easy to use with a remote control. In case you would like more power, you can attach two of the same models to generate more power for small houses. The internal use is only for freeze control of up to -30 degrees that allows the heater to work great even in extreme cold.

3. Quiet and Energy Efficient

Rinnai RUC98iN Ultra Series

Rinnai RUC98iN

  • Inddor Gas Heater
  • Natural Gas
  • Concentric or PVC venting option 
  • 199,000 max BTU

Even though gas tankless heaters are great to have around the house, there are some safety precautions that you need to be aware of. One of the best ways to be sure about the safety is to get the ones with an electric ignition. It helps with easy starting and is much safer than regular gas tankless heaters. This version of the Rinnai Ultra series has an electric ignition and is designed to be space saving especially for indoors and small places. This non-condensing water heater can vent through PVC pipes or through concentric venting options. Another reason why it’s great is that there is a no emissions design that helps it remain a safer option for the environment.

Up to 199,000 BTU can be produced with this heater while the energy factor is up to 0.96. It comes with isolation valves and pressure relief valves to make it more efficient. Users have the option to use the system with natural gas or with propane. Rinnai digital controllers can make the machine efficient and the right controller can also help you use this machine for commercial purposes too.

4. High Capacity Option

Rinnai RL75iN Natural Gas Tankless Water Heater

Rinnai RL75iN

  • Indoor Direct Vent
  • Large Capacity Heater
  • Natural Gas
  • 7.5 GPM - 9.4 GPM Options

The problem with many gas tankless water heaters is that their condensation properties use various gasses to help the water in heating instead of using the available gasses. Even though more heat is easily generated, it can be less efficient. The non-condensing ones are highly suited for smaller places and they are much cheaper. One of the best non-condensing ones is the Rinnai Gas tankless water heater. The heater provides about 10,300 BTU and up to 180,000 BTU. The heat and settings control can be with a digital control that gives off an indicator of error to keep the system safe.

This water heater also gives the option of being used commercially but users will have to get a separate controller for that purpose. This water heater can be used around smaller homes and apartments easily and internally. About 7.5 gallons of water per minute can be heated with this heater. Users who are conscious of setting a water heater internally can also set this one outside with ease. One of the best parts of this heater is that you can save money and energy with efficient heating.

#5. Rheem RTG-84XLN

Rheem RTG-84XLN 8.4 GPM Low NOx Outdoor Tankless Natural Gas Water Heater

Rheem RTG-84XLN

  • Natural Gas Tankless Water Heater
  • 8.4 gal/min. at 35-Degree Rise
  • UMC-117 remote control 
  • Low Nox Version

Why we like it: It is perfect for residential use even for bigger houses since it provides about 8.4 GPM at about 45 degrees rise. 

One of the problems that come with the outdoor water heaters is their usage and settings. Every once in a while, you may want to change the settings and it may be a hassle for the user. However, with the Rheem outdoor water heater there is no such problem because there is a remote control included that works up to 10 feet away to adjust the settings and turn it on or off without any hassle. This tankless water heater works with natural gas and should be installed outdoors only. Using it indoors can be highly dangerous.

It is perfect for residential use even for bigger houses since it provides about 8.4 GPM at about 45 degrees rise. It saves energy which allows it to be a better option than many others. The technology allows you to have hot water all day with safety and efficiency.The machine produces about 180,000 BTU. The heater is protected internally which saves it from freezing in cold weather, making it better for colder places.

#6. Rinnai RUR98iN

Rinnai RUR98iN Ultra Series Condensing Indoor Natural Gas Tankless Water Heater

Rinnai RUR98iN

  • Flow rate @ 70°(50°F)
  • Offers both Concentric and PVC
  • Tankless Rack System (TRS/TRW) Compatible
  • 1/2" Gas Line Compatible

Why we like it: The size is compact and can easily fit indoors; however, the water flow has a maximum of about 9.8 GPM. 

Sometimes you have to run the tap for a while before getting hot water. That water goes down the drain and is wasted. However, the Rinnai Tankless water heater helps in recirculation of that water to be heated again and used before it is drained into the waste line. This feature helps in saving precious water and saving money as well. Apart from this, one of the best things that you will find is that you will not have to get separate gas cylinders for this water heater. Your regular gas line can easily be connected and help you save on everyday cylinders.

The machine comes with the ability to accommodate both centric and PVC pipes for more options of venting. Another reason why this is a great option is that it has the ability to be connected to Wi-Fi for controlling the thermostat. The size is compact and can easily fit indoors; however, the water flow has a maximum of about 9.8 GPM. With energy star certification, customers know they have bought the right tankless heater.

#7. Takagi T-KJr2-IN-NG

Takagi T-KJr2-IN-NG Indoor Tankless Water Heater, Natural Gas

Takagi T-KJr2-IN-NG

  • 140,000 BTU. Voltage: AC 120V
  • 6.6 GPM max flow rate
  • Energy factor of 0.81-0.83
  • 37 pounds weight

Why we like it: This indoor tankless heater is perfect for residential use at it provides ample amount of producing heated water for smaller than industrial purposes. 

If you are looking for a tankless gas water heater that can easily fit indoors, this unit will be the perfect option for you. The heater uses natural gas to power up to 14000 BTU with a flow rate of up to 6.6 GPM. This indoor tankless heater is perfect for residential use at it provides ample amount of producing heated water for smaller than industrial purposes. The size is also perfect for apartments where you can easily set up your own system without having to worry about the dangers of heaters.

The system can easily be converted into a direct vent unit which means that you are less likely to go through long procedures of making a venting space for the heater. The design is made to be environmentally friendly and can be very cost effective. This model has switches to consider the altitudes of the fitting for a more enhanced and safer performance in higher floor apartments. With an energy factor of about 0.81 – 0.83 units, this heater is a perfect inlet for apartments and small houses.

#8. Takagi T-Kjr2-OS-NG

Takagi T-KJr2-OS-NG Outdoor Tankless Water Heater, Natural Gas

Takagi T-Kjr2-OS-NG

  • 19,500 - 140,000 BTU/hr
  • 0.82 energy factor
  • 6.6 GPM max flow rate
  • 37.9 pounds weight

Why we like it: Being powered by Energy Star makes it most energy efficient in the market with the energy factor being 0.82.

Most users are not comfortable with having tankless gas heaters installed inside the house. However, the ones that are made for outdoors usually malfunction when it gets too cold. The Takagi Tankless water heater is made to ensure that you can install this heater safely outdoors. The freeze protection keeps the heater running even in the most extreme temperatures. The system gives off about 140,000 BTU per hour maximum. It is suited for places with 2 or 3 bathrooms since the maximum water flow is about 6.6 gallons per minute. The heater works with natural gas.

The machine can easily be used for light heating systems and heating applications. Being powered by Energy Star makes it most energy efficient in the market with the energy factor being 0.82 units. Another model of the same design gives you the option to have it run on propane gas as well. However, it is very important to keep in mind that this heater is only for outdoors and installing it indoors can be highly risky. Even outside, the space-efficient design allows it to be very convenient.

#9. Rheem RTG-64DVLN

Rheem RTG-64DVLN Prestige Low NOx Indoor Direct Vent Condensing Tankless Natural Gas Water Heater

Rheem RTG-64DVLN

  • Direct Vent Indoor
  • 6.4 gal/min. at 35-Degree Rise
  • Low Nox Version
  • UMC-117 remote control

Why we like it: The direct venting machine can be controlled using a remote-control system. It produces 6.4 GPM at about a 35-degree rise. 

One of the many gases that are emitted with gas water heaters is a nitrous oxide or Nox and Nox is highly flammable and dangerous to the health. With other heaters, you will have to compromise on this factor. However, in recent years, a low Nox version of heaters has been developed which ensures that there is no or little amount of Nox released when the heater is running. This is highly important factor to consider as it can be dangerous for children. This model of the Rheem Gas water heater includes No Nox feature that makes this unit safer and efficient.

The direct venting machine can be controlled using a remote-control system. It produces 6.4 GPM at about a 35-degree rise. It is perfect for small homes and apartments. However, if you think your house requiresmore use, the EZ cable can connect two units together to create double-flow and therefore, double the temperature rise.  The unit comes with a 10-foot thermostat wire to set the temperature according to the preference of the users. The energy star certification ensures that the machine energy efficient.

Tankless Gas Water Heater Buying Guide

The following is my detailed guide to finding the most suitable tankless gas water heater for your house. You can find all the important details and the decisions that you have to make here before you purchase the unit of your choice. Also, if you are interested you can read our guide on the best-rated electric tankless water heaters here or if you are looking for something more powerful there are also commercial tankless water heater reviews here.

Consider the Size

The tankless gas water heaters are assigned a heating unit in BTU and energy efficiency to help it achieve a flow rate in GPM. These features come together to determine the size of the heater’s use and can help you find the one that will suit your living space. It can take about 31,000 BTU with 1.2 GPM of water flow; the cooler your area is, the more heat will be required. Flow rates are about the amount that you will get in your bathroom. An average for a medium-sized house will be about two showers that can be fulfilled in 6.6 GPM.

However, the size also concerns the energy efficiency. Most of the time, the bigger the unit gets the more gas it requires. Make sure to keep in mind the energy flow to check if it is too high. One of the best ways to ensure that energy is saved is by getting one that runs on gas but ignites electricity.

Exhaustion Properties

Of course, if your unit is running on gas, it will need a place to vent the residue. One of the decisions you need to make before considering the venting system is whether you are planning on putting your unit indoors or outdoors. In case you plan on doing it outdoors, there will be no gas issues to deal with. But indoors you might have to break a wall or find a way to make sure that the venting is outdoors unless you want your house full of gas.

Here you have two options; the direct vent and the power vent. Direct vents are used to pull in fresh air and then vent out the consumed air. These are great for indoor purposes as they keep the exhaustion well ventilated and are not difficult. For additional safety, you can go for the no Nox ones. These are safe from emitting Nitrogen Oxide which can be very harmful especially if you have children around the house. Power vents demand a bigger space for their exhaust vent so that they can get the ample air quantity for combustion.

Condensing or non-Condensing

Condensing and non-condensing are another one of the decisions that you will have to make with your tankless gas water heater. Condensing water heaters save a lot of money when it comes to installing a tankless heater. They become more energy efficient and emit cooler exhaust air than the noncondensing ones. Condensing heaters can use PVC instead of metal which makes a big difference in the money.

Noncondensing ones are a great option for outdoor heaters. These are cheaper than the others and are slightly smaller. They are great for mobile homes, cabins, or even camping.

Save it From the Cold

One of the most important things that you will need is to make sure that your tankless gas water heater is safe from the cold regardless of whether it is indoors or outdoors. Gas water heaters are the perfect way to ensure that there is maximum heat being generated so you are safe. However, if you are living where there is extreme cold, then you need to ensure that you have the internal system, and your unit is protected from the cold. This feature allows the heater to work regularly to give good temperatures and keeps the pipes safe from being frozen if you want to go a step ahead.

Tankless Gas Water Heater Comparison Chart

ModelBrandPower SourceWeight
RTGH-95DVLNRheemGas-Powered79 pounds
T-KJr2-IN-NGTakagiGas-Powered38 pounds
RL75iNRinnaiGas-Powered65.9 pounds
RUC98iNRinnaiGas-Powered82 pounds
T-KJr2-OS-NGTakagiGas-Powered38 pounds
RTG-84XLNRheemGas-Powered54 pounds
10011 ExcelGas-Powered20 pounds
RTG-64DVLNRheemGas-Powered54 pounds
RUR98iNRinnai Gas-Powered93 pounds
V65INRinnaiGas-Powered49.8 pounds


Tankless gas water heaters may be a little more expensive than tank water heaters, but they are highly durable and a top-rated tankless water heater is worth the money. They are energy efficient, some more than others, and help you be in a safer environment for water heating. It is highly recommended that people purchase a unit to help them save energy and money in the future. They are very safe since stored hot water can be prone to a lot of different mishaps and most of the time, they do not have a thermostat that can set the temperature.

With my guide, I hope to have cleared up many thoughts that come with the option of purchasing the best tankless gas water heater. My unbiased reviews are a way to show the greatest options on the market with different and very important features that need to be taken into consideration. If you are still confused, make sure to ask a professional for a better idea of which one will suit your needs. Keep in mind that you may have to spend a bit more money than you imagined, but in the long run you will be saving a lot of money and be helping the environment at the same time.


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