Best Gas Tankless Water Heater 2021

Gas tankless water heaters 2021 are the type of water heaters in which natural gas is used to heat the water in very little time. The working and heating process of these heaters is quite easy and simple. the integral part of these heaters is a heat exchanger, which is get heated by natural gas. In this article, we have discussed the detail, specifications, and reviews of the best gas tankless water heater of 2021. Keep reading this article to know all these details.

The capacity of tankless water heaters can be measured in GPM (maximum water flow) or BTU. If you are looking for a larger household, you should use a 10+ GPM heater. Similarly, a 6-7 GPM maximum water flow gas tankless heater can be suggested for a small household.

Moreover, the average EF rating of a tankless gas water heater is about 0.8 to 0.9, which means that 80-90% of the total energy will be consumed to heat the water. The remaining energy would be lost. The modern and efficient tankless heater having an EF rating of about 0.9 is considered the good ones because its energy loss is less than 10 percent.

Features of Gas Tankless Water Heater

Following are the features of gas tankless water heaters:

  • Gas tankless water heaters supply enough hot water in more than one shower or faucets at a time.
  • They require less space to set up as compared to a tank water heater.
  • They are easy to install and use, even you can set up these types of water heaters by yourself.
  • It can give you the supply of unlimited hot water in seconds instead of minutes.
  • Tankless gas water heaters also save your money so far due to the low cost of natural gas.

List & detail of best gas tankless water heaters of 2021

Here is the detail of the best tankless gas water heaters of 2021 given below:

1. Rinnai RU Sensei Super (Overall Best Gas Tankless Water Heater)


Rinnai is a Japanese company and is considered the best producer of gas tankless water heaters. They have produced many different models of such types of heaters. Rinnai RU Sensei Super is considered their latest and most efficient model having remarkable specifications.

Sensei Superseries has a terrific rating of 0.95 EF and it also has a 10% more efficient working as compared to an average tankless water heater. This type of heater can last for almost 20 years due to its high efficiency and working power. It is considered one of the high-rated tankless gas water heaters that earned the Energy Star Label.

These heaters range from 7 GPM up to 11 GPM maximum water flow whereas; the heating capacity of such models is about 199,000 BTU. You can install these heaters in almost all types of households. If you want to set up for a small household, you can pick a 7 GPM, 9 GPM for a medium-sized, and 11 GPM for a large household.

The advantage of using these products from a Japanese company (Rinnai) is that all the gas tankless heaters are very reliable and offer a better 10-year warranty as well.

There are many models like RU160ip, RU180in, and others. The ‘RU’ is the abbreviation for ‘Rinnai’ while the ‘160’ and ‘180’ represent the maximal BTU output, and the last letter symbolizes the ‘propane’ or ‘natural gas’.

In short, Rinnai Sensei Super is the most reliable and efficient tankless gas water heater. Initially, it was very expensive but now its cost is reduced to some extent.


  • Best gas tankless water heater having an outstanding energy-efficiency (EF= 0.95)
  • Achieved Energy Star Label.
  • Most successful models ranging from 7 GPM to 11 GPM.
  • 10-year warranty which is considered the best warranty.


  • It is more costly.

2. Rinnai V Series HE (Classic Model) Tankless Water Heater

It is the classic Rinnai model of the tankless gas water heater. It can last up to almost 20 years. V Series HE is the combination of three enhanced features: Rinnai Brand, Suitable Price & Reliability. It can cost up to almost $150 per GPM.

There are several models starting from a range of 5.3 GPM maximum water flow to 9.4 GPM having a maximum heating output of 199,000 BTU. Some of the V Series models could be scheduled by using the Control-R 2.0 mobile app so that you can put your tankless water heater to sleep mode whenever you don’t need it.

Moreover, it has the ability to heat a large amount of water to 140F immediately. Its heat exchanger (responsible for the heating process) has a warranty of 10 years. Its EF rating is about 0.82, the latest technology of 2021 has come with an EF rating of 0.9. It has an average energy efficiency with an 18% loss. So, you can’t get such a suitable model in a suitable price than the classic Rinnai V Series HE.


  • Best warranty of 10 years
  • Maximum water flows from 5.3 GPM to 9.4 GPM.
  • It is considered the cheapest Rinnai gas water heater.
  • Tried-and-tested by Rinnai


  • Require outdoor installation.
  • Its older models come with a 0.82 EF factor.

3- Noritz NRC66DVNG (Indoor Gas Tankless Model) Tankless Water Heater

This type of gas tankless water heater is developed by Noritz, a Japanese company. Their best model of tankless water heaters is 39 lbs NRC66DVNG. It is considered the most lightweight tankless gas water heater. It has two specifications; a single indoor unit and a condenser. The purpose of the condenser is to boost up the energy-efficiency. It also has two main disadvantages; larger size and heavy-weight.

As it is an indoor-only unit, so just be careful while installing it. It also has a condenser. You must have to channel the water condensate with suitable piping.

It has a 10-year heat exchanger warranty and a maximum hot water flow of 6.6 GPM. This model is considered suitable for small or middle-sized households.


  • Small and lightweight tankless water heater.
  • Support easier installation
  • Best-in-industry (10-year) warranty.


  • It is an indoor unit only

4- Takagi T-H3-DV-N (Energy Star Unit with Condenser) Tankless Water Heater

Takagi T-H3-DV-N is considered a less expensive gas tankless water heater. This type of tankless water heater is a combination of two factors. One is the use of natural gas and the other is having high energy efficiency. These models are most commonly used because of the low cost of natural gas as compared to electric or propane models.

The condenser plays an important role in gaining high energy efficiency because by attaching a condenser with a gas tankless heater we can increase its energy efficiency by more than 10%.

The best part of Japanese companies of tankless gas water heaters is that they offer a 10-year heat exchanger warranty. It can be the best choice for middle-sized as well as large households where the hot water requirements are more than its average needs. Because of its condenser, T-H3-DV-N is on the list of a few gas tankless water heaters that earned the Energy Star label.


  • Have earned the Energy Star label.
  • Have a Japanese best-in-industry 10-year warranty.
  • An affordable price.


  • Maybe it is difficult to install.
  • Only one model is available.

5- Rheem RTGH-95DVLN Prestige Tankless Water Heater

Japanese brands like Rinnai and Noritz are well known for the production of gas tankless water heaters. As far as the technology behind the tankless gas water heater is concerned, the US company named Rheem has come close to the Japanese Engineering techniques.

Rheem produces electric as well as gas tankless water heaters, but here we are discussing only gas heaters. So, Rheem RTGH-95DVLN is their most famous gas-powered model.

This model is the modern gas tankless heater having a built-in condenser. Due to the condenser, its installation becomes a little bit difficult. You have to drain the gathered water from the condenser.

 It has an EF rating of 0.94, so it is clear that you can’t achieve such a high energy efficiency without a condenser. This built-in condenser can raise an average EF of 0.8 to the massive 0.94, so only 6% of total energy is lost while using Rheem RTGH-95DVLN.

It contains intelligent electronic controls, which maintain the heating output as well as the safety of the heater. It can heat a large amount of water immediately and efficiently from 85F to 140F.

Due to the increased energy efficiency, low NOx emissions may be observed, because this model can extract an extra 10-15% of the energy out per ounce of natural gas. Rheem RTGH-95DVLN is a powerful gas water heater having a maximum hot water flow of 9.5 GPM, which is enough for a larger household too. Besides this, Rheem offers a 12 -year warranty on the heater exchanger. Its price is nearly $1200 which is highly affordable.


  • This model has a maximum hot water flow of 9.5 GPM.
  • Best US-based gas tankless water heater.
  • It has the highest energy efficiency having an EF factor of 0.94.
  • 12-year heat exchanger warranty (more than even Japanese water heater brands)


  • Difficult to install due to the condenser

Frequently Asked Questions

Q: What is the major drawback of a gas tankless water heater?

Ans: The main drawback of gas tankless water is that they are expensive as compared to tank-style heaters. Not all people can afford such costs.

Q: What type of tankless water heaters are suitable for a medium-sized household?

Ans: A gas tankless water heater having a capacity of 10 GPM is considered suitable for a medium household, as it will be able to supply enough amount of hot water for a small family of 5 to 6 members.

Q: Is the use of a tankless water heater valuable or not?

Yes, it is really valuable. Because the tankless water heats the water according to the demand and requirement of the user, instead of storing 5 or 6 gallons. So that you will never run out of water.

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