Best Tankless Gas Water Heaters | My Top 5 Picks

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“A friend from work has one just like it, and it works just fine. “

That’s a typical sentence I hear from people when they call me to take a look at their underperforming gas-powered tankless water heater.

What could go wrong?

Where do I start…it can be too noisy, it can mess with your water pressure, it might cause cold water “sandwiches,” the actual capacity of the heat exchanger might be much lower than the listed flow rate…the list goes on and on.

I’ve seen it all.

The information overload can get you the point of reconsidering the whole decision of going tankless.

If this describes you or someone you know, let’s be clear on one thing from the get-go – going tankless is probably one of the few best home-appliance decisions you’ll make in your lifetime.

The good news is, the confusion is not your fault – you just need the right help when choosing.

Who am I to speak about gas tankless water heaters?

I’ve been installing tankless gas-powered heaters for longer than I care to remember.

More importantly, since starting Plumber Spot (this site), I have compiled a substantial database. I did it to take my recommendations beyond opinion, into the field of data-based guidance.

If You’re in a Hurry – My Top Picks at a Glance

There’s only one gas-powered tankless heater that consistently maintained a rating of over 90% in all eight quality categories*.

It’s the Rinnai RUS75eN. The unit is available both as natural gas and propane-powered, and it comes in two sizes (6.5 and 7.5).

It’s the absolute king of the hill in terms of user satisfaction numbers.

*quality categories: temperature control, safety, energy efficiency, flow rate control, long-term reliability, user satisfaction, value for money, and installation/upkeep

About this guide

I did my best to present the results concisely and clearly, without boring you with unnecessary tech-talk and all the data behind the picks.

I also made an effort to adjust the picks so that all main types of tankless gas water heaters are represented – from home units for indoor and outdoor installation (natural gas and propane) to portable units.

A word about Rinnai nomenclature before we move on

Most of our top picks come from Rinnai. So, let’s take a moment here to go over what the names of the models mean. It can be confusing at first sight but it’s pretty straightforward.

Let’s take the RU160ip & RU180in as examples:

  • RU stands for Rinnai
  • 160 and 180 stand for the maximal output, eg. RU160in has an output of 160.000 BTUs
  • IN and IP stand for natural gas and propane respectively

Best Gas Tankless Water Heater Reviews – Top 5

#1 – Best Overall - Rinnai RUS75eN

Sale
Rinnai RUS75eN Hot Water Heater, 7.5 GPM, White
  • Energy and Space Efficient: Space-saving design conserves...
  • Optimal Water Pressure: High-performance 7.5 GPM hot water...
  • Instant Heating: Circ-Logic technology enables recirculation...

Specs

Hot water flow: two versions available – 6.5 or 7.5 gallons per minute

Fuel: propane or natural gas

Installation: Outdoor

Warranty: 10 years (on the heat exchanger) and 5 (on the parts)

Size and weight (of the 7.5 GPM version) : 22 x 14.5 x 35 “, 57.2 lbs

Defining features:

  • Space-saving design – typical Rinnai, boxed-shape with a small footprint
  • Available versions for both indoor and outdoor installation
  • Premium materials – built for durability and longevity

What makes it the best

At the moment, this Rinnai is the only non-condensing, gas-powered tankless heater with a user satisfaction rating of 95 % (or higher). It’s also the only heater that maintained 92+ percent throughout the process of putting this guide together.

If you know the market, you’d know that these numbers are nothing short of unbelievable – even the best units don’t work for everyone, and there’s always a slight chance of something being faulty on arrival.

All those numbers are so low with this Rinnai they are on the very edge of being statistically (in) significant.

Finally, it’s THE choice for a conservative buyer because it’s free of the frills that typically add 20-30% to the price (like voice activation).

Natural gas and propane version – both top-notch

The high ratings I mentioned above go for both the natural gas and the propane gas-powered version. The natural gas version tops the propane-powered unit by the slightest of margins.

Energy efficient with reliable temperature control

This is one of the three units that found its way to the top in all eight quality categories, including temperature control, energy factor, and safety.

Bottom line – if the hot water math works for you, the search might as well end with this Rinnai.

If you need something more robust, you might be better off with the runner-up (below).

PROS:

  • Fairly cheap for a Rinnai heater – probably top value for money in the Top 5
  • Fairly simple installation
  • High energy-efficiency
  • Energy Star certified

CONS:

  • Not WiFi ready
  • No recirculation technology

#2 – Best Condensing Choice - Rinnai Rinnai RUC80iN

Rinnai RUC80iN Ultra Series Natural Gas Tankless Water Heater,...
  • Concentric or PVC venting option
  • Up to .96 Energy Factor
  • The space-saving design allows installation almost anywhere

Specs

Hot water flow: 8 gallons per minute

Max BTU: 152.000

EF: 0.96

Fuel: natural gas

Installation: Indoors

Warranty:

  • Residential: Limited 12 years on the heat exchanger and 5 on the parts, 1 year on labor
  • Commercial: Limited 5-year for the exchanger and parts, 1 year on labor (with 5 years optional)

Size and weight: 10 x 18.5 x 26 “, 61.7 lbs

What’s better about it?

This model is the runner-up for one reason only – the price is still too high for most people. That’s what gave the classic RUS75 an edge over this state-of-the-art unit.

Why is it so expensive?

Because it uses almost all the energy expended to heat the water and wastes a measly 4%.

It’s a top-of-the-line condensing unit with an unparalleled EF of .96.

I do see it at the very top in a year or two, as soon as Rinnai finds a way to make it more affordable for the average buyer.

CONS:

  • Industry-leading energy efficiency
  • Lower venting temperatures make PVC vents an option
  • Easier venting system installation, especially if you go with PVC
  • Ultra-low emissions of NOx

PROS:

  • Expensive

#3 – Great Choice for Big Homes - Rinnai V94IN natural gas tankless water heater

Rinnai V94iN Natural Gas Tankless Hot Water Heater, 9.8 GPM
  • Energy and Space Efficient: Space-saving design conserves...
  • Optimal Water Pressure: High-performance up to 9.8 GPM hot...
  • Enhanced scale detection lessens possibility of serious,...

Specs

Hot water flow: 9.8 GPM

Fuel: natural gas

Installation: Indoor

EF: 0.82, UEF: 0.81

Size and weight: 14.04 x 9.27 x 26.9 “, 46.3 lbs

Defining features:

  • Compactly built – ideal for big homes with little room for installation (like attics or pantries)
  • Design to have minimal impact on water pressure
  • App-controlled – programmable timers, schedules, and vacation mode

Is it right for you?

If you have a larger home with multiple hot water outlets that often run simultaneously, the beastly 9.8 GPM of this Rinnai will meet all those demands (and more).

The higher the demand, the higher the chance that something might go wrong regarding temperature control and water pressure.

Based on what I’ve seen with this unit, the people who weren’t fully satisfied cited one main reason – the fact that the max. temperature setting is 120.

The optimal shower temperature is 112, which means that this will be a moot point for most people.

My note: It’s not too complicated to circumvent the 120-degree maximum, and I’ve seen people do it.

Keep in mind that all other specs are based on the listed maximum, and it’s best if you leave this alone – 120 degrees is more than enough.

PROS:

  • Probably the best balance between output and size in the Top 5
  • Indoor installation means little to no risk of damage from the elements
  • Industry-leading warranty terms

CONS:

  • Not all parts needed for installation are included
  • Heavier than most units – 62 lbs

#4 – Condensing Runner Up - Takagi t h3 DV condensing natural gas water heater

Takagi T-H3-DV-N Condensing High Efficiency Natural Gas Indoor...
  • Endless hot water, On-demand usage, Compact, Space saving,...
  • Computerized safety features, No pilot light to have to...
  • Safety features include freeze, overheat, surge protection,...

Specs

Hot water flow: 9.8 gallons per minute

Fuel: natural gas

Installation: Indoor

Energy efficiency: EF: 0.82, UEF : 0.81

Hot water T range: 100-185 ºF

Size and weight: 10.75 x 17.75 x 22.5 “, 59 lbs

Sound: 55 dB

Defining features:

  • Features a condenser – which adds at least 10% to the energy efficiency
  • Safety features are fully computerized
  • Meets the Ultra-Low NOx standards
  • The copper alloy used for the primary heat exchanger transfers heat 25 times better than stainless steel
  • All controls are integrated

What makes this Takagi so good

This is the one high-capacity unit that gave Rinnai models a run for their money.

Now, to be perfectly honest, there’s one main reason I’m putting this natural gas water heater front and center. It’s ‘condensing.’

If you didn’t read the whole guide, “condensing” means that it uses two heat exchangers (primary and secondary) to utilize more of the energy created by the gas.

In practical terms, that means more power delivered, higher energy efficiency, and a more compact design.

Copper alloy of the primary exchanger

The primary exchanger of the Takagi is copper alloy, and it’s about 2,500% better at transferring heat than stainless steel, which jacks up the energy efficiency, too.

In my opinion, condensing units still have a way to go in terms of balancing out the energy savings with other performance factors.

That’s what I love most about this Takagi – comparable performance to non-condensing units in its price range with a higher EF.

PROS:

  • Superior safety features
  • Features a condenser, which means higher efficiency and lower venting temperatures
  • Energy Star certified
  • Ultra-low emission of NOx
  • No pilot light

CONS:

  • Condensing units are somewhat more complicated to install

#5 – Best Budget Choice - Rinnai V75 gas heater

Sale
Rinnai V75iN Natural Gas Tankless Hot Water Heater, 7.5 GPM
  • Energy and Space Efficient: Space-saving design conserves...
  • Optimal Water Pressure: High-performance up to 7.5 GPM hot...
  • Enhanced scale detection lessens possibility of serious,...

Specs

Hot water demand capacity: up to 7.5 GPM

Fuel: natural gas

Installation: Indoor

Hot water T range: 98ºF – 140ºF

Energy factor: 0.82

Size and weight: 14.04 x 9.27 x 26.9 “, 45.6 lbs

Other features: leak and scale detection, temperature lock, low NOX emissions

Defining features:

  • Leak detection feature shuts off the water to minimize potential damage
  • Scale detection lowers the risk of buildup damage
  • Temperature lock feature – only you can change the settings

Why it’s my top budget pick

V in the name stands for Value Series.

The Rinnai V75 tops the list of budget-friendly gas-powered heaters for two main reasons – it’s a solid value for money.

If you ask me, finding a good discount is a much better way to save than buying cheaper.

The Rinnai V75 is up there with the best of them in all other quality aspects – from temperature control to reliable flow rates.

PROS:

  • Exceptional value for money
  • Safe – leak & scale detection, temperature lock control
  • Budget-friendly
  • Available as both

CONS:

  • Energy factor not as high as that of a condensing unit

Honorary Mention

# – Best Tankless Gas (Propane) Water Heater for Camping & RV's - Camplux Pro

Camplux 2.64 GPM Tankless Propane Water Heater, Outdoor Portable Gas...
  • Compact,Light Weight Portable Design-12.8...
  • Easy Installation for Instant Hot Water-It only takes you a...
  • CSA Safety Testing Standard Ensure Your Safety-Flame failure...

*I’m including this Camplux to make this guide more complete because I’ve seen a bit of confusion about what “gas heater” means. The Camplux series is powered by propane, not natural gas.

Specs

Hot water demand capacity: 1.58 to 2.64 GPM

Fuel: propane

Type: portable

Water pressure range: 3 to 4 minimum to 110 PSI maximum

Defining features:
  • Light and compact – great choices for dynamic people on the move, like campers and RVers
  • Meets the CSA safety standards – anti-freezing and overheating protection, automatic shut off at high water temperatures
  • Heat exchanger designed to minimize both gas consumption and noise
Is it right for you?

This entry is actually six products from Camplux – their PRO series.

That’s why the specs are not precise – because it all varies from unit to unit.

The critical decision point – the volume of hot water you need on your trips.

On the low end, you have the 1.58 GPM unit that can deliver 28,000 BTUs per hour. On the high end, you have the Camplux PRO BW422, with a listed volume of 4.22 GPM and a maximum power output of 110,000 but per hour.

One thing they all have in common is consistently high ratings across all quality aspects.

Bottom line: It wasn’t even close in the portable category.

PROS:
  • Light, compact & portable
  • Easy to set up and use
  • Great shower handle
  • Solid overall safety
CONS:
  • Costs more than similar units from lesser brands

Reference Info & FAQs

The all-important sizing

Choosing well when it comes to the size of your tankless gas water heater is critical for long-term satisfaction and savings.

Water flow rate (GPM – gallons per minute)

GPM of a gas tankless water heater will tell you how many gallons per minute it can deliver.

It’s typically listed “as is,” but the more accurate way to interpret the piece of information is in congruence with your hot water rise (difference between the groundwater temperature in your area and your hot water settings).

For the list of “best tankless gas water heater,” I made an effort to only choose units and brands that clearly explain how to calculate the GPM capacity you’ll need. The good ones will deliver on-demand hot water just as reliably as a storage tank.

The size math

BTU (British Thermal Units)

BTU describes how much gas energy you need to raise the temperature of one pound of water by one degree F.

How high of a BTU you’ll need depends on the number of hot water appliances, the volume of hot water your family uses, and even how they use it.

By “how,” I mean how often more than one appliance uses hot water at full capacity.

For example, if you have someone in your home that takes those long 40-minute showers, you might need a higher BTU.

Alternatively, you can go with a gas tankless heater that features adjustable flow-rate technology.

These heaters drop the flow rate and maintain the temperature when they “sense” that more hot water is being spent than they can heat.

Energy efficiency (energy factor & energy savings)

The energy efficiency of gas tankless water heaters is reported as EF (energy factor) or UEF (Universal energy factor).

It describes how much of the total gas energy is used to heat the water.

Gas-powered units are more energy-efficient than your run-of-the-mill tank heater because there are no standby or cycling losses.

They are, however, not as efficient as electric units.

On the other hand, gas is cheaper than electricity, which pretty much offsets the energy efficiency, at least if your primary concern is the cost of running.

Water temperature rise

Make sure to take the time to understand this part when looking through the sizing guides of natural gas tankless water heaters.

The listed flow rate only makes sense if you account for the temperature rise, especially if you’re in the colder parts of the country.

How does a gas tankless water heater work?

Both natural gas tankless heaters and propane units work in pretty much the same way.

They are attached to the cold water supply line and equipped with a flow sensor. Once this sensor is triggered by opening the tap, it activates the burner.

The unit then “sucks” water into the heat exchanger and circulates it until it reaches your desired temperature.

This gives you a continuous flow of hot water on demand.

Fuel type – natural gas or propane

Propane and natural gas water heaters are similar, and the choice between the two will come down to what’s more convenient for you.

In my experience, people who do have natural gas power lines choose to use them. It’s cheaper and more convenient than re-fitting your hot water installations.

Gas or electric

Go with gas if you’re looking to lower your energy bill and you’re OK with investing more upfront.

If you don’t have a gas supply line or you want to spend less initially, you’ll be better of with an electric unit (you can read about my top electricity-powered picks here).

Do they use electricity?

Yes, a vast majority of natural gas tankless water heaters need electricity to run the system, except some of the small portable ones.

How long do they last?

I’ve seen units that easily last for 30 years, and I’ve seen people claiming warranties and replacing the unit twice within the first year.

If you initially choose well, the longevity of your gas tankless water heater will come down to water quality (read: hardness), maintenance and usage.

Warranties

The best gas tankless water heaters typically come with a warranty in the range of 6 to 15 years (the latter is an exception).

The critical part here is the warranty on the heat exchanger. As a rule of thumb, don’t settle for anything less than six years on the exchanger and three years on the parts.

Whole house or point-of-use

For point-of-use, I’d go with electric units rather than natural gas tankless water heater (let alone propane). They’re more energy-efficient, typically smaller, and save space because they don’t need venting.

For whole-house use, both can work well, and the choice will ultimately depend on current installations.

Top tankless water heater brands

Most of the best gas tankless water heaters, in my opinion, and based on my data, come from the following brands:

  • Rinnai
  • Rheem
  • Noritz
  • Takagi
  • Palms
  • Camplux
  • EcoSmart

Customer service

A high level of customer service is paramount. I’m a fan of Rinnai’s customer service.

If you look at the specs and you’re still unsure what’s right for you, they typically do a great job of pairing you with the unit( based on your set of factors – groundwater temperature, capacity, temperature rise).

I rated the companies in that department based on existing natural gas tankless water heater reviews and only considered those who provided the highest level of customer support (4-star or higher).

Vent configurations

Combustion creates C02, which makes good ventilation a must when installing a gas tankless water heater.

These are the vent types that pair well with a tankless unit:

Power vent

An electric fan is installed on top of the unit, and a blower pushes the excess heat and residue gas out.

Because they are powered, they have the flexibility to be installed both vertically and horizontally. This might be a factor if the space you’re installing the heater in is limited.

They are also more energy-efficient because they re-use the already heated gas (otherwise wasted).

Finally, because the temperatures are not as high as in other vent types, some of them allow for PVC piping – a considerable decision point for many people.

Direct power vents

If there’s no enough space to provide air for combustion, a direct power vent might be your solution.

In standard power vents, the air is only pushed out. In direct units, it’s also pushed in using the same vent.

Classis vent – atmospheric

Standard atmospheric vents are the most commonly used vent types for tankless gas water heaters. The principle is simple – the hot air/gas rises and is released outside the house through a vertical vent pipe.

If you’re getting a gas tankless water heater and plan to use a standard atmospheric vent, make sure that everything works properly and without blockages (especially if the heater will be sharing the vent with other appliances).

Direct standard vent

This type of venting is used in similar scenarios like direct power – when space doesn’t allow for combustion.

Coaxial vent chambers are used to draw air in and out.

Concentric

This is not a venting type per-se. The word “concentric” describes the pipe profile used for this vent; it’s a pipe-within-pipe system, if you will. The outer chamber is used for the intake and the inner for the exhaust.

You can pair it with any of the vent types we mentioned, but the pipes’ materials will depend on the venting.

How water quality affects tankless gas water heaters

By water quality, I’m primarily referring to water hardness because scale buildup (caused by hard water) is the no.1 cause of critical failures in gas tankless water heaters.

It’s also the main reason behind reduced efficiency, which, in turn, increases costs and negatively affects performance.

If this describes your water, you might want to think about pairing your gas tankless water heater with either a water softener or an anti-scale filter.

Noise

One common misconception that I keep hearing about is noise being an unavoidable downside of going tankless and using natural gas heaters to do it.

Here’s the skinny on that – you can indeed expect some noise as they fire up to heat the water, but that noise shouldn’t go beyond 90 decibels.

If it does (to the point of becoming an issue) or if you hear sounds when the heater is not working, there’s likely a problem.

I’ve responded to calls of people complaining about noise only to find out that it’s coming from some other appliance siphoning water and creating a vacuum.

Bottom line – noises will not be a factor with a good tankless gas water heater. You’ll likely be installing it out of sight, anyway.

Are they safe?

With proper installation and venting (that accounts for CO2), a tankless gas water heater is a very safe appliance.

I’d say that they are safer than their tanked counterparts because there’s no tank.

No tank means no risk of pressure buildup or explosion.

Safety features

The best tankless gas water heaters out there are equipped with additional safety features, life AFR sensors, exhaust temperature monitors, hi-limit switches, freeze protection, and overheat cut-off fuses.

Explaining what each of these does is beyond the scope of this guide – the important part for you is that the presence (lack) of these safety features is a factor in reaching the safety rating of a gas water heater.

Are tankless gas water heaters worth it?

The initial cost of gas tankless water heaters is higher than both tankless electric models and tanked units. But, the higher initial prices are canceled out with each year of use.

They’ll shave off hundreds of bucks from your energy bill per year.

If you consider the convenience of having hot water on demand, I’d say that they’re definitely worth it.

Instant hot water on demand at a lower price – what’s not to like about that.

Is Rinnai better than Rheem?

What is the best gas tankless water heater to buy? Rinnai, Rheem, or something else?

This is a question that I see in my inbox at least once a week. While my list of top picks might give you an impression that I prefer Rinnai, I’d say that I have no preference.

Rinnai just happens to make more units that fit what I’m looking for here.

Rinnai & Noritz

I also get a lot of questions about the Rinnai-Noritz connection – in spite of what many people think, the two brands are not one and the same. It’s true that they both come from Japan, but they feature different technologies.

Condensing or non-condensing

A condensing gas tankless water heater is the more energy-efficient of the two types because it uses a dual heat exchanger to lower the energy wasted.

Non-condensing are your typical units with a single heat exchanger that are somewhat less efficient.

The future of the tankless gas water heater industry is condensing; there’s little doubt about that.

But, I wouldn’t say that it’s the immediate future. The condensing units still need to improve to justify the higher initial cost for an average buyer.

Bottom line – there’s only one condensing entry on the list of top picks – the Takagi t h3 DV. It’s by far the best tankless gas water heater among the condensing units (in my opinion).

Low NOX emissions of tankless gas water heaters

If this is the first time you’re hearing about it, NOX refers to nitrous oxide gas emissions (toxic, reactive greenhouse gasses).

In the tankless gas water heater market, “low NOX” and “ultra-low NOX” have become the standard over the last few years.

This is all in response to the increasing restrictions on NOX emissions.

What it means for you

In my experience, the low NOX units have a superior system of mixing fuel (is. natural gas and air), which goes beyond adhering to the emission guidelines.

It means that a “low NOX’ unit is more reliable and energy-efficient, especially long term.

In a word, they’re worth it for reasons beyond reducing NOX.

Freeze protection

While a good gas tankless water heater will feature some sort of protection from freezing, it doesn’t mean that it can function normally in freezing temperatures. 

This protection is temporary and is designed to give you some time when that cold wave hits to either winterize the system or stop using it to prevent damage.

In my opinion, the best freeze protection systems come from the top brand – Rinnai.

What’s better about Rinnai

Firstly, all of the crucial parts inside a Rinnai heater are equipped with ceramic heating tiles, which fire up when the sensor ‘notices’ a below-freezing pressure drop. That’s the primary protection.

If that fails for whatever reason, there is a secondary system in place. This secondary system is triggered by its autonomous sensor and turns the natural gas heater on and off for short spans. It will do so continuously until the freezing passes.

One thing to note here is that both systems require power and gas to run. This means that you should always drain the system when you plan to be away for prolonged periods.

The warranties do not cover freeze damage.

My tip: A good alternative for doing this manually every time is installing a set of solenoid valves. These will drain the system on their own every time the power goes out. They are not cheap but are worth every penny in headache saved.

What you can do

In terms of freeze protection, there’s very little you can do apart from choosing well to begin with. However, you can protect the pipes and valves leading to and from the gas heater.

To do this well, use wrap insulation or heating cables and wrap the pipes. For optimal protection, apply both.

“Remote control” – nice-to-have, not a must-have

I’m putting the words remote control in quotes to stress that what you’ll see listed is not actual remote control (the kind you’d have for your TV) but a corded control unit.

While it is convenient, I don’t see it as a primary factor because you won’t be setting your tankless unity every day.

Stainless steel or PVC vents

For most of the natural gas heaters, I listed in my top 5, the manufacturer calls for the use of stainless steel for the vents (AL29-4C).

It all comes down to the temperatures developed in the tankless units. PVC is only listed to be used as flue material for operating temperatures of up to 150 degrees Fahrenheit.

Any higher than that, and you’ll need to look at CPVC or PPE (listed for 194 and 230 degrees Fahrenheit, respectively).

Just as a reference, AL-29-4C stainless steel is listed for use with operating temperatures of up to 550 degrees Fahrenheit.

My note: One thing I always mention when asked bout this is the fact that, in most states, PVC and CPVC are not on any official lists of venting materials. That tells you all to need to know when choosing between PVC and steel for your tankless unit vent.

If you decide to go for PVC after all, read the tankless gas water heater reviews from existing customers and search for experiences with the vents. Some of the condensing natural gas heaters are so energy efficient that the final exhaust comes out lukewarm.

Is it easy to install?

I see the term “easy to install” thrown around like a playtoy in the reviews of the tankless gas water heaters; I’d say that it’s a secondary factor at best.

Here’s why – if you’re wondering if you can install it yourself, it’s probably best if you didn’t.

If your skill and experience are at a level where you’re confident that you can indeed do it yourself, you won’t see a significant difference between the top-rated units.

Conclusions and Future Updates

To keep it relevant at all times, I update this guide with new data and reviews on a regularly. I do my best to stay on top of any changes in manufacturing practices and outsourcing.

For you, this means that this guide is evergreen, and you can use it even if you don’t choose today.

Just bookmark it and consult it when you’re ready.

If you aren’t looking for a gas heater in particular, check out our overall best tankless water heater reviews.

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