Best Natural Gas Tankless Water Heater

Natural gas is the primary fuel source for water heaters. It is generally more cost-efficient than electricity and some utility companies offer rebates for switching from an electric-, to a gas-powered water heater. A gas burner continually heats the water in a storage tank from the bottom of the unit. The best Natural Gas Tankless Water heater is the most reliable product for house use.

1. Rinnai RL75iN Natural Gas Tankless Water Heater:

Rinnai RL75iN

If you are looking for the best water heater for residential and commercial purposes, then Rinnai RL75iN may be the best solution.

Its flow rate ranges from 7.25GPM- easily enough for 2 to 3 washrooms. Temperature ranges from 98̊ F-140̊ F for residential purposes and commercial purposes temperature reaches 160̊ F, for this configuration the other controller must be purchased. Temperatures are set by a push-button on the front and are displayed on the LCD screen.

You also get two options for the fuel source: natural gas or propane. Later it became more expensive but also more efficient, which means save more money in the long term.

It has a cool temperature lock system that prevents unexpected changes to water temperature.

It has a scale detection system uses to indicate a build-up of scale. We see white and papery stuff in pipes and can radically reduce the lifespan of your water heater. It is a very useful tool to alert you for the maintenance required and will also help keep your water heater ticking for a long time to come.

It contains an energy factor of 82 for both natural gas. The propane makes it highly energy-efficient and granting it the famed Energy Star Certificate. It is also good for your wallet as you will be energy savings. Its warranty spans 5 years for parts and 12 years for heat exchangers.


  • Flow rate occurs up to 7.5 GPM which is enough for 3 washrooms.
  • The commercial temperature reaches 160̊ F
  • Maintenance became much easier because of the scale detection system.
  • Temperature lock safety
  • The long warranty time period
  • Energy factor of 82 natural gas and propane


  • Costly
  • Does not come with a kit of ventilation.

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

Takagi T-KJr2-IN-NG

The Takagi T-KJr2-IN-NG represents the first water heater run by natural gas. Natural gas heaters work by heating with a gas burner. So, they have innate benefits over their electrical brothers such as cost to operate.

That able to heat the water at a fast rate, and working during a power outage. They are less energy efficient compared to electrical models due to heat loss. The T-KJr2-IN-NG suffers from the same problem.

Heat loss is in the form of exhaust and so extra costs in installing and buying venting equipment. It will be required to get this unit operational. The good news is you get options of a vertical (through a roof) or horizontal (through a wall) ventilation set-up.

Takagi is known to make high GPM machines, with their T-M50 model having an industry-leading 14.5 GPM. This isn’t a T-M50, but the T-KJr2-IN-NG follows in a similar vein, with a maximum flow rate of up to 6.60 GPM – enough for small to medium houses with 1, 2, and possible 3 washrooms.

Energy factor ranges from 0.81-0.83 which is defined by the hot water’s amount made per unit of fuel used an average day. It turns out, this is a pretty good number compared to average tank gas heaters about 0.6-0.7. Still, it’s is less than electric heaters which can about 0.97-0.99.

On top of the AFR sensor, the Takagi also comes with a water and exhaust temperature safety control, and an internal freeze protection system. It makes for a feature-heavy unit that means you can leave it on auto-pilot for most of the year.

Temperatures range from 99 °F to a scalding 167 °F, so you’ll have no issues getting to your desired heat level. The T-KJr2-IN-NG is one of the highest-rated indoor heaters and for good reason. It has a good temperature range and an amazing flow rate.


  • Durable design with an excellent warranty
  • Solid maximum flow rate
  • Very high-temperature range
  • Good energy efficiency for a tankless gas water heater
  • Option for vertical and horizontal venting
  • Long warranty period
  • Energy factor higher than tanked models (but lower than electric)


  • Higher installation cost due to required ventilation

Rheem RTGH-95 DVLN 9.5 GPM

3.Rheem RTGH-95 DVLN 9.5 GPM Natural Gas Tankless Water Heater

This is a great natural gas tankless water heater for big households or small/medium households with high demand. This is one of the best tankless water heaters! Someone could take two showers, run the dishwasher, hand wash a pan, and do a load of laundry all at the same time! It’s a condensing unit, which is the most energy-efficient gas option on the market.

All that power and efficiency come at a cost that will make it very efficient. If you have a large demand for instant hot water, this is a great investment. It’s easy to install, works quickly and quietly, and can compete with any tank model in the flow department.

With this Rheem, the coldest climates will never cause a drop in pressure or temperature and you do not have to compromise on functionality, ever. There’s a built-in electric blower to help out with venting, too. That’s something a lot of other large models neglect to include. It includes a remote control in the box, so you don’t need to buy anything separately.


  • The high flow rate of 9.5 gallons per minute (GPM)
  • Heat three full-flow showers at once
  • It’s ideal for larger households, even 4-bedroom and larger.
  • Capable of operating at altitudes up to 8,400 feet.


  • It’s the most expensive gas mode

Rinnai V65eN

4.Rinnai V65eN Natural Gas Tankless Water Heater

V65eN is the perfect combination of high efficiency, comfort, and value in natural gas tankless water. This water heater is ideal for small to medium homes or remodels, compact, easy-to-install, reliable, and perfect for outdoor locations. Rinnai products provide peace of mind with warranties that surpass the competition.

If space is tight in your house and you want to fully capitalize on removing the old water heater that’s now stashed in a utility closet. So you have a plumber install the V65eN on an outside wall, freeing up the closet space, cutting your gas bill, and getting more hot water for your utility dollar. Not bad for a day’s work.

Other aspects of this low-cost appliance make it appealing, such as its 6.6 gallon-delivery rating. Rinnai rates it as suitable for homes with single or 1.5 baths. It is certified for installation in mobile homes. It comes equipped with an enhanced scale detection feature, which helps reduce long-term and serious damage to the unit.


  • Lightweight and Compact
  • Energy Factor of 0.82 / Uniform Energy Factor of 0.79
  • 10,300 BTU (Minimum) / 150,000 BTU (Maximum)


  • Not suited for larger homes
  • Must be mounted outside


What does the “Low NOx Mean ??

Energy efficiencies edit More tangible cost savings are defined when comparing the energy efficiencies of gas heaters with low NOx emissions with conventional flued types. Gas heaters with emission problems flued and inherently lose substantial energies in the form of hot flue gases to the atmosphere. In addition, the placement of flued heaters is greatly impaired due to flue installation restrictions.

How do you size a natural gas tankless water heater?

How to Select the Right Size Tankless Water Heater:

  1. Determine the maximum number of devices you want to run and their total flow rate. Then, add up their flow rates (gallons per minute). …
  2. Determine required temperature rise. …
  3. Sizing Example: An average shower will be between 104–106° and uses 2.6 gallons of water.

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