Best Natural Gas Tankless Water Heater Reviews and Buying Guides (Top 5 For 2018)

best natural gas tankless water heater

Here is a complete guide to the best natural gas tankless water heater currently available on the market. In this review, we will list down the top 5 alongside with their pros and cons, and buying guides when you are about to purchase one for your home. If you are interested to see why we think they are worthy contenders, then keep on reading.

When talking about water heaters, it is vital to know the different aspects of having a gas or an electric water heater. But, let’s not get ahead of ourselves just yet.For starters, gas tankless water allows you to have a higher supply of hot water. Furthermore, they are a perfect investment if you have many family members who love to take showers. It will also give you enough hot water for dishwashing, laundry and other activities.

Meanwhile, the electric ones might be cheaper, but there are certain drawbacks that could make you go against them.

Top 5 Comparison Table

Product Name



best gas tankless water heater
  • Dimensions: 11.2 x 17.8 x 24.9 inches
  • Weight: 59 lbs
  • Price: $$


rinnai gas tankless water heater reviews
  • Dimensions: 14 x 9.3 x 23 inches
  • Weight: 50 lbs
  • Price: $$$


  • Dimensions: 18.5 x 9.8 x 27.5 inches
  • Weight: 82 lbs
  • Price: $$$


  • Dimensions: 17.3 x 13.2 x 27.4 inches
  • Weight: 75 lbs
  • Price: $$$$


Bosch Gas Tankless Water Heater Reviews
  • Dimensions: 8.7 x 16.7 x 25.8 inches
  • Weight: 35 lbs
  • Price: $$$$$


The 5 Best Natural Gas Tankless Water Heaters Reviewed

1. Takagi T-H3-DV-N 

Featuring an innovative design, the Takagi T-H3-DV-N heater is a perfect addition to your home or your restaurant. 

It features a highly efficient water flow. When we compare it to electric water heaters, it is needless to say that you will have hot water almost immediately. It has a fantastic hot water flow of ten gallons per minute - more than enough for all your hot water needs.

Furthermore, what’s great about this product is the fact that it comes with an abundance of safety precautions. The heater has a freeze control, as well as an overheating management tool. In addition, if it ever breaks down, there are troubleshooting diagnostic codes that can help get an idea where the problem is.

It comes with a power direct vent construction, and you can also connect it to various units found in your home. Moreover, it can provide you with an endless supply of hot water.


  • You won’t run out of hot water, so there is no need to worry about it in advance.
  • It features a durable design that will last you for many years to come
  • You can install it without too much hassle. However, it would be better if you could let a technician do it instead of you.
  • The manufacturer made sure there are enough safety precautions that will allow it to run seamlessly. 


  • It is not a cheap gas heater. You will have to seriously think about investing in it before giving up your hard earned money.
  • Some users have reported that they have received damaged packages. 
  • If it ever breaks down, the cost of the repair could be substantial. 

2. Rinnai RL75iN 

rinnai gas tankless water heater reviews

This natural gas tankless water heater is one of the current favorites on the market. Its design might look simple, but that is the best part about it. It will not take up too much space in your house, so you don’t have to think about storage in advance.

Furthermore, if you have owned a similar model by the same manufacturer, you might be able to use the same venting ducts. However, a technician should carefully examine your home before you install it.

Speaking of installation, you will be happy to know that you will not have any trouble setting up this model. The manufacturer will also send you a manual you can use while installing it, and everything is clearly explained in it.

This heater provides you with an 82% of thermal efficiency, which is a fantastic result. In addition, it also performs well in extreme weather conditions. Therefore, if you live in a particularly cold area, you don’t have to worry about your hot water supply.


  • It will save you storage space in your home.
  • This water heater is energy efficient, so you can expect a reduction in your bills.
  • The design is straightforward, and cleaning is not too complicated
  • The installation is easy 


  • It can only run three fixtures at any given moment
  • The temperature can sometimes fluctuate.
  • If it leaks, it will leak water directly onto the heat exchanger. That could give you serious problems and the repair would be expensive

3. Rheem RTGH-95DVLN

If you have ever researched tankless water heating units, then you probably already know that the electric ones are often the most energy efficient. However, that statement is not entirely true if you take a look at Rheem RTGH-95DVLN.

This tankless water is 94% efficient, which is outstanding when compared to other tankless gas units. In addition, it is a safe heater to keep at your house. Its high-quality design allows you to feel secure, and it is highly unlikely that it will leak.

Furthermore, the main feature of this water heater is its digital display. It is easy to read and not really complicated to use. But, if you ever have any doubts, there is a manual you can use to learn more about it.

It also comes with a remote control, as well as a thermostat cord.


  • You can install the venting system outside or indoors
  • Its energy efficiency is exceptional and comparable to electric tankless water heating units.
  • It comes with intelligent electronic controls that can help you keep it as safe as possible 
  • There is a self-diagnostic system that helps you install in properly and maintain for many years to come.


  • You can get the spare parts from the manufacturer, but you will have to pay for the repairs yourself.
  • It is noisy
  • Users report that it can break down easily and its lifespan is too short for the price tag
  • Customer service may be slow

4. Navien NPE240S-NG

Navien is a popular water heater manufacturer, and it's no wonder most people love their designs. The same goes for their NPE240S-NG natural gas model.

If you are looking for a space-saving water heater, then this could be the best option for you. You can hang it on a wall - it will not take up any floor space in your home.

Furthermore, this premium condensing water heater is highly efficient, and it will allow you to have hot water fast. Even though it is compact, you don’t have to worry about running out of your supply - it can provide enough hot water for your whole family.

What’s interesting about this model is that it comes with two stainless steel heat exchangers. Most water heaters have only one, so this means that you will be able to heat the water faster.

Lastly, the design also features an intelligent preheating technology.


  • It will not give you trouble during the installation. You can install it quickly and without too much stress.
  • High energy efficiency hence will save you money on your bills.
  • The manufacturer included two heat exchangers for faster heating. Therefore, you will not have to wait for too long to get hot water. 
  • It is a low emission tankless water heater


  • You have to flush it with vinegar annually
  • It is a high maintenance water heater, which means that you will spend a lot of money every year just to keep it in top-notch condition. 
  • It can sometimes switch itself off 

5. Bosch 520PN LP

Bosch Gas Tankless Water Heater Reviews

If you have a small family that doesn’t require a great quantity of hot water, then this Bosch model will spark your interest.

For starters, it is not a bulky water heater, so you will not have any trouble finding enough storage space in your home for it. In addition, the design also features Piezo technology that allows you to ignite it without using electricity.

It is a small water heater with a 78% of energy efficiency, which means that you cannot expect it to provide you with a lot of hot water. However, if you have average needs, it is a great option that will surely prove its worth in the future.

The best part about it is that it weighs only about 35 pounds. Therefore, installing it should be a breeze.


  • It can provide a small family with enough hot water to meet everyone's needs
  • It will heat water only when you need it, so you will be saving money at the same time.
  • The push-button ignition is a safer option for basements and cabins.


  • It is an expensive option, even though it doesn't provide you with the same features that other bigger water heaters offer.
  • You can have only two hot water applications at the same time 
  • It doesn't come with a temperature display - the technology is a bit outdated.

Gas Tankless Water Heater Buying Guide

Before you go out and purchase this heating unit, it is vital to mention a few key factors you should be paying attention to. To help you reach a better decision, here is a list of things you should consider:

The Size of Your Household

You might have a large family that tends to use multiple hot water fixtures at the same time. Because of that, a gas tankless water heater is a fantastic choice for you. However, if you live alone or in an apartment, you probably don’t need a whole-house water heating system. It is vital to determine your needs beforehand. Otherwise, you will probably spend a lot of money on a unit that just won’t pay off in the future.

Can You Install It Properly?

Before you install these heaters, you have to check if your house can accommodate them. As you probably already know, these types of water heaters require you to meet certain venting demands. It would be best if you could hire a technician to check if you can fulfil all the requirements.

Can you pay for the installation?

In regards to our previous point, the installation of a gas water heater will probably cost you a lot more than you might have thought. Therefore, before delving further into the matter, it would be wise to calculate the costs in advance and see if your budget can handle them.

Will you be able to survive the fluctuating gas prices?

We all know that installing an electric water heating unit means that you will have higher electricity bills. However, electricity rates are somewhat stable. Meanwhile, gas prices could surge in the next couple of years. The decision is yours, and it will depend on your needs and preferences. But, it is important to take the rates into account before making your purchase.

What kind of technology are you looking for?

Some tankless gas units come with digital displays and a variety of safety precautions. However, the least expensive options often feature an outdated technology. Still, that doesn’t mean that they are poor quality, although there is a high chance they will fail you in the near future.

What will you do if it breaks down?

This type of heating units are known for their complicated repairs. Even if you find a fantastic technician, it still means that you will have to pay a high fee. These water heaters are complex, and they require more maintenance than you might think.

Can you afford an annual maintenance fee?

A tankless gas water heating unit is an investment that could last you for more than ten years. However, if you don’t take care of it properly, it can easily break down. You have to schedule annual maintenance for it, and a technician should properly clean it every year. Even though you might think you can do it all by yourself, these water heaters have complicated parts, and you will quickly lose your patience servicing them.

>> Looking for a suitable tankless water heater to incorporate with your home's floor heating system? Check out this article <<

Gas Water Heater Installation

If you are looking to purchase a gas tankless water heater, then you probably want to know how you can install it. However, even though DIY projects are a fantastic way to test your own skills, we would highly recommend you to contact a professional to install it for you.

There are many guides online that could help you install this type of water heater properly. Besides, if you have already installed one before, you will be happy to know that the process hasn’t changed that much.

Nevertheless, installing these heaters are not a simple task. A professional will be able to do it quickly and without too much hassle. In addition, he will know how to do it safely. One wrong move when installing this sort of heating unit and you could damage it forever.

Gas Water Heater Common Problems

We have already mentioned that these units can sometimes experience a few problems. In addition, those issues can lead to expensive repairs that could easily make you go over your “water heater maintenance budget.”

Here are some of the most common problems you will probably encounter.

Mineral Buildup

It goes without saying that it is important to take proper care of your water heating unit. Even the traditional water heaters are prone to mineral buildup.

The scaly buildup can seriously impact your maintenance costs because it will be difficult to remove it if you have left it that way for too long. Therefore, it is, without a doubt, wiser to just contact a technician every year and have him check your water heating unit thoroughly.

A professional will know how to clean it properly, and he will also check it for any other faults.

Warning Messages On The Display

If your gas tankless water heater has a digital display, there could be some alarming messages there.

It could show an “Exhaust Blockage” message, which is an indicator that there are some issues regarding your venting. If you call a professional, he will use special equipment to check the pipes. The equipment will show even the smallest leaks which we often fail to recognize.

However, if you want to check where the problem is, you should first take a look at the pipes. They should be properly connected and in one piece. If there are holes, even tiny ones, it is essential to replace them as soon as you can.

A blockage could also indicate that there is something stuck in the vents. That could mean that there is a potential rodent infestation, or that birds or wasps have built a nest there. Whatever the problem is, a professional will know how to solve it.

Cold Water

As you probably already know, certain gas water heaters require you to wait a little bit for the hot water supply. However, if a family member has used the water supply before you, it could lead to cold water flow.

There is nothing to be alarmed about, though. That just means that there was a small amount of hot water stuck in the pipes when you went in to shower. Therefore, you first received the remainder of the hot water, and then you were hit with cold water. The water heater started heating a new supply, and it just needed a bit more time to get it to you.

This all ties in with the position of your water heater. If it's too far from your bathroom, then you will have to get used to it - there will be a small amount of cold water at the beginning of your shower.

Not Enough Hot Water

When you purchased them previously, you probably thought that it will be able to provide you with an endless supply of hot water. However, if you are using too much of it in multiple locations at the same time, the heater could shut down.

There aren’t many solutions to this problem. You can restrict the hot water use in your house, or you could replace the heater with a bigger unit. In addition, you could also purchase a second unit that will allow you to use both water heaters for different purposes.

When To Replace A Hot Water Heater

Your water heater probably has a decent warranty. But, that doesn’t mean that it will last forever.

There are some clear indicators that will tell you when it’s time to switch to a newer, possibly tankless unit.

For starters, if you notice that there is rusty water coming out of your showerhead, there is a fair chance that your water heater is rusty as well. You can try draining the heater, but if the water is not clear, you will have to replace it. Otherwise, it could start developing holes soon.

If your heater starts producing rumbling noises, then it is probably time to make the switch. Furthermore, if you notice any leaks, then it is better to get rid off it before it starts ruining your home. Leaks can destroy carpeting, as well as your belongings. Moreover, your house could get infested with mold.

Therefore, a gas tankless water heater is an ideal choice if you want to avoid these problems. It can last you for years, and because it doesn't have to use a tank, you will only have to service it once a year.

Final Verdict

Takagi T-H3-DV-N Tankless Water Heater

Our research has shown all the pros and cons of different tankless gas units. However, the winner has to be Takagi T-H3-DV-N tankless water heater.

Its design lets you install it in your home or your restaurant, and it is a highly efficient unit that will certainly save you a lot of money. Furthermore, the safety precautions are a fantastic addition because they will give you an added sense of security while using it.

The installation process is straightforward, and the unit will certainly last you for years. Users often talk about its durability and its high-quality design, and the features it comes with will allow you to keep it in top-notch condition. Its qualities speak for themselves and, with just a few flaws, it is worthy of its price tag.

Although it went against some well-worthy contenders, Takagi T-H3-DV-N is undoubtedly the best natural gas tankless water heater currently on the market.

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