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🥇 7 Best Tankless Gas Water Heater Reviews: An In-Depth Guide for 2021

Back in the day, traditional water heaters were an inconvenience for more reasons than one. Being obsolete in built and technology, these units were bulkier, occupied large spaces across homes, and used to consume a lot of energy, which blew up the bills.

The fact that these units used to pollute the environment was also a shortcoming big enough. However, people didn’t have many choices in those years and therefore, were forced to settle for less.

Today, as technology evolves, the choices for water heaters have increased and so does the power they pack. Modern tankless gas water heaters fill the gaps for their traditional counterparts, making them the best investments to date for anyone who live in cold weather conditions.

These heaters are energy-efficient, environmental friendly, and compact in size. Their durability is excellent and speaks for them. Most reviews suggest that people, who use tankless gas water heaters, have reportedly saved 30-40% on their gas bills, which happens to be an impressive claim and a catalyst for their market demand.

Over the years, the variety for tankless water heaters gas type has dramatically exploded. Every product boasts of a feature list, which seems worth a wad of cash and better than anything you can find on the shelves. However, truth be told, whatever promises the best isn’t necessarily the best, and sale pitches can trick you easily, which begs a question: how can you spot the right product in a pool of so many?

We have compiled an in-depth user guide to help you find the best tankless gas water heater within your choice of features and budget. Our experts have looked into every detail, consulted plumbers, and waded through a lot of reviews to decide which products should acquire a spot on the list. So, here’s the lowdown we have got to help you get your money’s worth. Let’s dive right in. 

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1. Rinnai RUR98iN Ultra Series Tankless Water Heater

If you’re looking for an impressively powerful water heater among the class of ‘as usuals’, you aren’t alone. And, if you don’t want to shell out huge sums of money to bring it home, we don’t judge you.

However, you would be happy to know that there’s a water heater in the market, packing all the punch you need. It’s robust, feature-packed, and fits all your cold-weather requirements quite seamlessly. Meet RUR98iN—the editor’s choice for the best gas water heater 2021 and in the next two minutes, you will get to know why.

Firstly, Rinnai RUR98iN offers two venting options – PVC and Concentric, so you can choose either of them based on your household requirements. Cheap water heaters have poor venting mechanism, and the maintenance costs usually are expensive. By providing a handy range of venting options, Rinnai RUR98iN ensures a plenitude of savings and no installation hassles.

Secondly, the 9.8GPM flowrate, complemented by cutting-edge circulation technology, is a salient feature, which makes this water heater a worthwhile investment for a 5-room household. While the massive GPM rate provides an optimal water flow, the recirculation technology lets you ditch the need of installing an extra dedicated pipe for consistent supply.

And lastly, Rinnai RUR98iN helps you conserve over 96% energy, a factor that also draws its environmental friendliness in the spotlight. Here is a separate article on Rinnai Tankless Water Heater Reviews.

Rinnai RUR98iN in a Nutshell


Innovative Recirculation Technology for Uninterrupted Water Supply
Installation Type — Indoor
Concentric and PVC venting options
Condensing Technology features dual heat exchangers
9.8GPM flowrate
Up to 0.96 Energy Factor
WiFi capable


An ideal bargain for a large household
Endless water supply assured
Compact as a suitcase
Zero-fuss installation
Substantial cost savings


Very expensive

2. Rheem RTGH-95DVLN Direct Vent Tankless Gas Water Heater

If you have fallen head over heels for the Rinnai RUR98iN’s flowrate, but don’t have a load of cash to invest, Rheem RTGH-95DVLN saves your day. A low-priced option, this water heater offers premium features but at a reduced prize. During our market research, one of the biggest pain points that emerged about tankless gas water heaters is the messy indoor installations.

Most of the units pose a lot of challenges when it comes to installing them, the reason being their vents. However, Rheem RTGH-95DVLN cuts a figure for itself for its amazing venting architecture that pulls the plug on safety concerns. Other than this, it comes with a self-diagnostic system that helps you get through the installation process in a slick manner.

The digital display is a notable feature, which shows the temperature as well as the maintenance codes. These codes provide visibility into the internal workings of the heater and alert you of those times when it needs troubleshooting.

Our favorite takeaway from the Rheem RTGH-95DVLN’s feature list is the remote control facility. No matter how much water heaters claim to be safe, nobody’s comfortable with touching them.

However, with the remote control facility, it’s pretty handy to adjust the temperature without any fear. Towards the end, it’s important to mention that Rheem RTGH-95DVLN is 94% energy efficiency, which ensures huge savings on your monthly electricity bills. You can also read detailed Rheem Water Heater Reviews.

Rheem RTGH-95DVLN in a Nutshell


9.5GPM flowrate
Smart electronic controls for efficient handling
Equipped to work as high of an elevation as 9840ft
Freeze protection for -30*F temperatures
Two-pipe PVC venting mechanism
Self-diagnostic system for easy and fast installation


Fit for commercial and residential purposes
Advanced technology build ensures 100% efficiency
Capable of functioning in the harshest of cold weather conditions
Maximum savings assured


Tad pricey
Requires professional help for installation

3. Takagi T-KJr2-IN-NG Indoor Tankless Water Heater

Beat the cold weather with Takagi’s best-selling natural gas indoor water heater, which makes for an ideal deal if you’re scrambling for the low prices. However, make no mistake: there’s nothing you can’t get under a reasonable tag. Coming at a good 6.6GPM flowrate, Takagi T-KJr2-IN-NG water heater ensures a gurgling rush of water from multiple showers as well as faucets across a household at the same time. Now, when a compact heater provides such an optimal flowrate, temperature fluctuation is an immediate consequence.

Fortunately, there’s a fairly decent functionality that doesn’t allow that. Takagi T-KJr2-IN-NG comes with thermistors installed at both its inlet and outlet, which provide for continuous temperature monitoring.

Since you can keep tight tabs on every variation, the problem of fluctuations is rightly addressed. On the downside, Takagi T-KJr2-IN-NG doesn’t offer a seamless venting option and forces you to pump in cash for a 4’’ stainless steel vent for its smooth run instead.

Takagi T-KJr2-IN-NG in a Nutshell


6.6GPM flowrate
140,000 BTU
Inlet and outlet thermistors for constant temperature monitoring
Up to 0.81-0.83 energy factor
4’’ stainless steel vent a prerequisite


Generous flowrate for the price
Suitable for big households
Near-zero temperature fluctuations
Small-sized and lightweight
10-year heat exchanger warranty – a talking point!


Expensive venting requirements

4. Eccotemp FVI-12-NG High Capacity Tankless Water Heater

Eccotemp has built a professional tankless water heater for smaller households, which earns its place on the list. The FVI-12-NG model is a feature-rich, cost-effective option for those living in one-room apartments and may not need higher flowrates for their daily requirements.

Out of all, what’s clearly the biggest selling point of this machine is its promise of lifetime warranty, a factor that speaks highly of its quality and reliability. Its power venting option is another value point.

Since Eccotemp FVI-12-NG comes with a built-in exhaust fan, all the gases are expelled outside your living ecosystem in the outer surroundings, which keeps your room cool and clean. However, some caveats and limitations must be noted.

Eccotemp FVI-12-NG isn’t completely a gas-based water heater. While natural gas powers it, both the ignition and LED-temperature display consumes energy. But, this doesn’t mean your energy bills will shoot up.

The amount of electricity use by these components is non-excessive and fairly balanced to better suit your budgetary limitations, so your money is well taken care of.

Another downside—and a disappointing one at that—is the need for professional installation help to avail the lifetime warranty. You will have to hire a professional to get this water heater installed and be eligible for the lifetime warranty benefits.

Eccotemp FVI-12-NG in a Nutshell


3.6GPM flowrate
Efficient power ventilation suitable for any apartment or a cabin-like office
Digital temperature display for constant monitoring
Electronic ignition system


Safe and reliable
Stainless steel vent offers durability


Requires professional help for installation

5. Bosch Greentherm C1050 Propane Tankless Water Heater

Bosch Greentherm C1050, a top-selling water heater model under the propane class of devices, packs a lot of charms; however, what gives it an edge is its mobile application feature. Though it has no part to play in improving the heater’s cold-weather performance, it does make it easy to figure out the right sizing calculations at the time of installation.

Another competitive feature is its innovative bypass technology, which doesn’t result in standby heat loss and keeps the water heated for a long time. This means, you don’t have to re-heat the water or experience the sudden bursts of cold water, also known as a cold water sandwich effect.

Since water heated once stays as is, energy is saved aplenty, and your bills stay well under the limit. Speaking of the flowrate, we can’t ask better than 10.7GPM at 35*F frosty weather. Even in the areas where the temperature soars up to 50*F, Greentherm C1050 is engineered to deliver at a generous 6.8GPM.

And, as far as the energy factor is concerned, this Bosch machine is 96% energy-efficient, making it the best tankless gas propane water heaters to date. The shortcoming, however, is that this water heater has an aluminum vent, which is less durable and tolerant of wear and tear. 

Bosch Greentherm C1050 in a Nutshell


Bypass Technology for benchmark temperature stability
10.7GPM flowrate
Concentric up-and-out venting for single boilers
Mobile application for sizing and technical documentation downloads


Consistent hot water supply
Limited re-heating requirements
Multiple venting options for both residential and commercial requirements
96% thermal efficiency
Cost-saving benefits


Steel heat exchanger instead of the existing aluminum one would have sweetened the deal a little more

6. Takagi T-K4 Natural Gas Outdoor Tankless Water Heater

With a brilliant maximum flowrate of 8GPM, Takagi T-K4 tankless water heater is a highly competent machine for bigger requirements. Talk about cold climates and watch this beast supplying eight gallons of water every minute—enough for two showers and a faucet to run at the same time.

Though that makes Takagi T-K4 a solid fit for a mid-sized household, 8GPM isn’t the final best it can deliver. This water heater is capable of producing gases to supply more than 8GPM, so that you don’t have to think twice using it in extremely cold weather conditions.

Powered by anti-freeze technology, Takagi T-K4 prevents hot water from cooling off and ensures an all-season performance. What’s more, there’s a Hi-Limit switch that ensures water temperature stays within safe limits, an important addition for a gas heater in order to avoid the cold water sandwich effect.

From the business perspective, Takagi T-K4 has laid down a quick and seamless contact support process, which has gone ahead to make a name for itself. Within a few minutes of making a call, an executive will come on the line to assist you and answer your questions.

Takagi’s official website, on the other hand, has a library of resources, which includes user manuals, installation guides, troubleshooting guides, and even a rebate finder. It doesn’t take a genius to understand that Takagi has prioritized customer experience and has gone to lengths to excel in it. 

Takagi T-K4 in a Nutshell


8.0GPM flowrate
Anti-freeze technology
Hi-limit switch and Inlet and outlet thermistors for temperature monitoring
No venting required


Perfect for a mid-sized household
Very reliable
Excellent customer support


Low energy factor

7. Rheem RTGH-84XLN Natural Gas Condensing Tankless Water Heater

When it comes to keeping multiple hot water requirements for a bigger household, Rheem RTGH-84XLN leads the pack. Widely known for its energy- and water-saving benefits, this Rheem machine offers premium features available at a much more affordable package.

Flexibility-wise, this water heater provides an option to decrease the water flow in the pipes as need be, which eventually helps you save over 1,100 gallons of water per annum. The next advantage is its low fixture capability, which means that even while ensuring water flowrate at 8.0GPM, Rheem RTGH-84XLN will start delivering hot water at 0.40GPM, so temperature fluctuations are near-zero. The notification alerts are also a plus.

This water heater displays warning codes on its digital display, thereby providing you situational visibility into when it needs troubleshooting. In addition to this, Rheem RTGH-84XLN comes with an electric blower, which vents the gases into the outer surroundings, and a remote control, which helps you easily operate it.

Rheem RTGH-84XLN in a Nutshell


8GPM flowrate
Built-in blower for venting the gases
Freeze protection up to -30 degree F
Digital display for periodic


Capable of operating at high altitudes and with low-fixtures
Environmental friendly


Size too large

Choosing the Best Tankless Gas Water Heater

The market is flooded with a variety of tankless water heaters. And, every mini machine promises a might. However, it’s folly to spend your hard-earned money on the basis of empty, tall claims. A little bit of research and analysis is necessary to get good value for money. Below are a few aspects that you must consider before buying a tankless gas water heater.

 1. Look for the Right GPM

Manufacturers might roll out an attractive sales pitch, saying that you will never run out of hot water. However, the fact is—you can if you exhaust the unit’s flow rate. Before jumping with both feet in the market, take your time to analyze your daily water requirements, and buy a water heater with a flowrate that meets them—effectively and consistently.

Buying a tankless unit with a low flowrate capacity would mean that you’ll overtax the unit and experience a cold shock. The bigger your house is, the more powerful your water heater must be.

2. Take Note of the Temperature in Your Region

Cold weather conditions vary from region to region and so does the water temperature. The colder the water is, the more your water heater will have to work to heat it up.

So, it’s highly recommended that you must choose a tankless heating unit based on your area’s temperature. This is important to make a smart purchase while also ensuring that your water heater isn’t burdened to meet your requirements.

3. Match Your Unit with Your Home’s Gas Type

Tankless water heaters are classified into two varieties—Natural Gas and Propane. While both of the models are identical in cost, GPM, and energy factor, they couldn’t be interchanged. Hence, it’s advised that you must buy a unit that’s compatible with your home’s gas type.

FAQs on Gas Tankless Water Heaters

Q1. Why are the benefits of a tankless water heater?

A1. Contrary to tank water heaters, tankless units are durable, energy-efficient, and can last up to two decades. Besides, their smaller size means that the water heats up quickly and is delivered exactly at the moment you switch on a faucet.

Q2. What is the duration of warranties on tankless water heaters? And, what do they cover?

A2. Tankless water heaters have a warranty of 10-15 years. And, different companies have different warranty policies. Most of them offer coverage for parts, labor, and replacements of components for around one, three, or five years. However, it’s noted that warranties on tankless water heating units are applicable only they are professionally installed.

Q3. What should be the average temperature for bathing and showering?

A3. The default setting of most tankless gas water heaters is 120*F, and some people might prefer 140*F. However, mind you that such a setting can scald your skin in as little as six seconds. The recommended setting for bath is 96-110 degrees, and for showering is 105 degrees.

Q4. How Long Does It Take To Drain a 50 Gallon Water Heater?

A4. Keeping the 50 Gallon Water Heater clean for your regular and long time use is very important. Doing regular checkups as well as flushing the water stored inside allows your heater to be ready for longer use.
However, if you are willing to know how long it will take to clean the heater, it is mainly based on the rate of flow that you have. So you can easily calculate the GPM and the total capacity.
For example, if the capacity is 50 Gallons and then the rate of flow is 10 GPM, it will take about 5 minutes to completely drain the water that is left inside.

Wrapping Up

For someone who experiences cold weather conditions for more than half year, a water heater isn’t a matter of choice, but a call for necessity. So, it’s wise to invest in a unit that promises the best of everything and delivers sustainably in bitterly cold environments.

To help you make that decision faster and easier, we played by the numbers and gave out all the details on the best tankless gas water heaters available in the markets today. Installing one will not only ensure continuous supply of hot water in your home, but will also save you energy and by extension, the money you spend on electricity bills.

If you have any suggestions on how we can improve our reviews or are of the opinion that we have missed out on a crucial detail, drop a line to us in the comment section below. For more such in-depth reviews, keep visiting this space.