6 Best Tankless Gas Water Heaters In 2023 (Based On Specs)

Having the best gas tankless water heater is the most cost-effective way to get on-demand hot water.

There are little things in our households as convenient as immediate access to a virtually unlimited supply of hot water.

All gas-powered tankless water heater comes with two major advantages:

1. Unlimited hot water without the need for a tank. No tank means you can save space; the house looks nicer, and, most importantly, you have peace of mind when it comes to all your hot water needs.
2. Powered by natural gas. Natural gas is by far the most economically viable power source for a tankless water heater. Both alternatives (electricity or propane) can double the cost of heating water. Tankless gas water heaters come with a higher initial cost; however, you’re saving more than $100/year on hot water heating costs because natural gas is that much more cost-effective.

The immediate access to demand-on hot water at the lowest possible cost makes natural gas-powered tankless water heaters very appealing. As far as hot water needs are concerned, installing one is one of the best long-term decisions for most households.

Note: Gas tankless heaters have a higher capacity than electric ones. That’s why Rinnai, the best propane or natural gas tankless water heater producer, offers a range of capacities (or sizes) for all of their units.

With such a vital part of your household, it makes sense to pick the best possible gas tankless water heater that covers all your hot water needs.

Looking at specification sheets of all top-notch tankless gas water heaters, we can see that there are 3 key metrics that we need to check before buying a gas-powered tankless heater:

3 Key Specs To Look Before Buying A Gas Tankless Water Heater

Gas tankless water heaters are quite easy to understand. Natural gas is used to heat the heat exchanger (the integral part of every heater), which in turn heats the water. The whole process from you turning on a shower and the hot water reaching the showerhead takes less than 10 seconds.

Despite the simplicity of the heating process, there are several key differences between gas tankless water heaters that we need to be aware of before buying the heater. These include:

• Capacity (in GPM (maximum water flow) or BTU). A gas tankless water heater can handle the hot water needs of most households. These usually have 6-9 GPM maximum water flow. For bigger households, look for 10+ GPM heaters with 180,000-199,000 BTU. For smaller households, a 6-7 GPM maximum water flow gas tankless heater can be appropriate. Just remember; it’s better to choose a bit more powerful heater to be safe.
• Energy-efficiency (measured by Energy Factor rating or EF). An average tankless gas heater will have an EF rating of 0.8 to 0.9. That means that 80% or even 90% of natural gas will be used for heating (with 10% to 20% energy loss). The most energy-efficient tankless gas heaters can exceed an EF rating of 0.9. Those are the best ones because they have less than 10% of energy loss.
• Price (100$ per 1 GPM is average). The initial cost of gas tankless heaters can be relatively high. It’s completely normal to pay more than $1,000 for a good tankless water heater (it’s a 20-year investment, after all). A good rule of thumb is that for every additional 1 GPM of maximum water flow, the price of the heater will increase by $100. Of course, the best tankless gas water heaters can cost much more. Those, however, have high energy-efficiency and will be cheaper in the long-run because of the natural gas savings.

Other important specifications include a warranty (especially warranty for heat exchanger – should be 10 or more years), Energy Star label, and the output water temperature interval.

All in all, the Japanese are the overall best producers of gas tankless heaters. Rinnai heaters, for example, are the most well-known and reliable natural gas heaters you can buy. Here is the full list and comparison of the best gas water heaters with a list of key specifications. Below you will also find reviews of every heater in the list:

List Of The Best Natural Gas Tankless Water Heaters

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

Japanese company Rinnai is arguably the best producer of natural gas tankless water heaters. They have several models available – including the classic Rinnai V Series HE (#2 pick). However, their newest and most successful model with incredible specifications is the Rinnai RU Sensei Super.

The Sensei Super series is one of the very few tankless gas water heaters that earned an Energy Star label. With the spectacular 0.95 EF rating, it is about 10% more efficient than an average tankless water heater. These heaters last for 20 or more years; 10% savings over 20 years can result in $100s, if not $1000s saved just because of the additional energy-efficiency.

Given the cutting-edge specs Rinnai has managed to achieve, it’s no wonder they offer several RU Sensei Super model capacities. They range from 7 GPM maximum hot water flow (130,000 BTU) up to the most powerful 11 GPM maximum water flow with the heating capability of 199,000 BTU. 199,000 BTU units are the biggest tankless water heaters.

With such a range, you can install the Rinnai RU Super Sensei in every household. Just pick 7 GPM for a small one, 9 GPM for a standard-sized household, and 11 GPM for a larger household.

The 11 GPM Rinnai RU199iN Sensei Super, for example, is the most powerful residential gas tankless water heater. It can deliver up to 199,000 BTU heating capability; this is the absolute maximum for a residential hot water heater (200,000 BTU is the limit).

The good thing about Japanese engineering is how very reliable pretty much all Rinnai gas tankless heaters are. In fact, they go the extra mile with the warranty as well. Most of the top heaters have a 10-year warranty for the heat exchanger; with the purchase of Rinnai Sensei Super, you get a 10-year warranty on the heat exchanger. That’s literally the best warranty in the industry.

There are several Rinnai Sensei Super tank models, and Rinnai uses serial numbers for each of them.

Here’s how you navigate the Rinnai Sensei Super tankless water heaters: You will see models like RU160ip, RU180in, and so on. The ‘RU’ stands for ‘Rinnai’. The ‘160’, ‘180’ numbers are the maximal BTU output. For example, RU160ip has an output of 160.000 BTU, which equals about 9 GPM. The last letter ‘p’ or ‘n’ designates ‘propane’ or ‘natural gas’, respectively.

All in all, Rinnai Sensei Super is the safest, most reliable, and most cost-efficient tankless water heater. Its initial cost is quite high, but this is a long-term investment, and the real cost comes from natural gas usage, which is heavily reduced due to the extra high energy efficiency of the Rinnai Sensei Super.

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#2 Rinnai V Series HE (Best Tried-And-Tested Classic Model)

The V Series HE is the classic Rinnai model of a tankless gas-powered hot water heater. This is the tried-and-tested heater with a great track record. The expected lifespan of the Runnai V Series HE gas heater is 20 years.

The best thing about the V Series is the trio of sought-after qualities:

1. Rinnai brand. Best brand in the world of gas tankless water heaters, with proven reliability and high-quality devices.
2. Affordable price. The newest Rinnai gas tankless heaters can cost a pretty penny (more than $150 per 1 GPM). The V Series HE can cost as low as $100 per 1 GPM; that’s a 33% reduction in the initial price.
3. Reliability. Nothing beats a no-nonsense water heater. Install it once, check it regularly, but other than that, you have peace of mind; it didn’t cause major problems in the past, and chances are it won’t in the future. That’s the beauty of the classic tried-and-tested HVAC devices.

The V Series can heat a large amount of water to 140˚F almost immediately. The heat exchanger responsible for the heating process comes with a top-of-the-line 10-year warranty.

However, the one caveat the older V Series HE model has, is the energy efficiency. It has an EF rating of 0.82. This did make one of the most energy-efficient gas tankless heaters 10 years ago. However, in 2023, the new condensing technology in the modern natural gas tankless heater can reach and exceed an EF rating of 0.9. In short, Rinnai V Series HE has an average energy efficiency with 18% energy loss, while the modern Rinnai RU Sensei Super (#1 pick) operates at only 5% energy loss.

Several models are available with different capacities, from the small 5.3 GPM maximum water flow with 120,000 BTU heating capacity to the biggest 9.4 GPM with the maximum heating output of 199,000 BTU.

Despite being the old-school model, the Rinnai V Series HE heaters come with the Control-R 2.0 mobile app. With the app, you can schedule hot water needs during the day; the ‘vacation mode’, for example, is handy. When you don’t need the gas tankless heater, you can put it into sleep mode.

For this price, reliability, and the Rinnai brand behind you, you won’t find a finer model than the classic Rinnai V Series HE.

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#3 Noritz NRC66DVNG (Lightweight Indoor Gas Tankless Model)

Noritz is a Japanese company that makes HVAC devices. Their best gas tankless water heater is the 39 lbs NRC66DVNG model. This is the most compact and lightweight tankless gas model on the list. It comes with two specifics; it’s an indoor-only unit and has a condenser, which boosts the energy efficiency.

Noritz NRC66DVNG has an above 90% energy efficiency. The EF rating is 0.91. Such highly efficient use of natural gas as a power source is only possible with a water condenser. The condenser can move the energy efficiency from 0.8 EF rating to 0.9 EF rating. Usually, it comes with two drawbacks; increased size and weight of the gas tankless water heater.

What makes the Noritz NRC66DVNG such a great tankless gas heater is that the addition of the condenser doesn’t increase the weight of the unit (it does increase the dimensions a bit, to 6.7 x 13.8 x 23.6).

You need to be careful when installing the Noritz gas tankless heater because this is an indoor-only unit. Because it needs to be installed indoors and has a condenser, you need to channel the water condensate with the appropriate piping. For venting, the 3” Schedule 40/80 PVC, PP, or CPVC can be used. Just be aware that the IK-WV-200-1-XX-LF valve kit is necessary for the installation, but you have to buy it separately (it costs about $90).

Given its reliability and 10-year heat exchanger warranty, the Noritz NRC66DVNG is one of the best small gas tankless water models.

It comes with a maximum hot water flow of 6.6 GPM. That is appropriate for small or middle-sized households. To give you an idea of what 6.6 GPM means – most people buy the Noritz NRC66DVNG when replacing a 40-gallon heater.

In the long term, having an energy-efficient tankless water heater that uses cheap natural gas is a financially smart investment.

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#4 Takagi T-H3-DV-N (Energy Star Unit With Condenser)

Takagi T-H3-DV-N is one of the most cost-saving gas tankless heaters. According to the U.S. Government-issued Energy Guide, the estimated yearly energy cost of using Takagi T-H3-DV-N for hot water needs is as low as $172.

That is the result of two factors:

• High energy-efficiency.
• Using natural gas. Tankless water heaters powered by natural gas are, on average, much more cost-efficient than propane or electric models because of the lower price of natural gas.

In fact, the great cost optimization has earned the Takagi T-H3-DV-N a coveted Energy Star label. That’s a label only a few gas tankless hot water heaters can obtain. The best Rinnai units, for example, have the Energy Star label.

The secret behind the high energy efficiency of the Takagi gas unit is the condenser. As we’ve stated before, adding a condenser to a gas tankless heater can increase energy efficiency by more than 10%.

One additional effect of achieving high yield (energy-wise) from natural gas is reducing the levels of nitrogen oxides. Takagi T-H3-DV-N has ultra-low NOx emission; the high natural gas yield is partly a reason for such a good reduction in NOx emissions.

The great thing about the Japan-based tankless gas water heater producers is that they offer the above-standard warranty – Heat exchanger (10 years), parts (5 years), labor (1 year). It is nice to see parts and labor covered; however, the main warranty you want to have is the 10-year heat exchanger warranty.

Takagi T-H3-DV-N has only one model: the powerful 10 GPM one. It is most appropriate for middle-sized to larger households who have above-average hot water needs.

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#5 Rheem RTGH-95DVLN Prestige (Best US-Made Gas Tankless Water Heater)

Japanese were the first to perfect the natural gas-powered tankless water heaters; brands like Rinnai and Noritz are good examples. In the US, the company that has come close to Japanese engineering as far as the gas tankless water heaters are concerned is Rheem.

Rheem makes both electric and natural gas tankless heaters; their more well-known gas-powered model is the Rheem RTGH-95DVLN.

This is the modern gas tankless heater with a built-in condenser. The moment you look at the EF rating of 0.94, you know that high energy-efficiency is impossible to achieve without using the condenser. The Rheem condenser can propel the RTGH-95DVLN for an average EF of 0.8 to a super high of 0.94. That means that Rheem RTGH-95DVLN producers only 6% energy loss.

What is more, the intelligent electronic controls maintain both the optimum heating output and increase the safety of the RTGH-95DVLN model. In such a way, the Rheem gas tankless water heater can heat water anywhere from 85°F to 140˚F very quickly and most cost-effectively.

With the increased energy-efficiency comes low NOx emissions. That’s because the Rheem RTGH-95DVLN can squeeze an additional 10-15% of the energy out of every ounce of natural gas.

Obviously, the addition of a condenser makes the installation a bit more difficult. You have to drain the water that is gathered in the condenser. If you have an existing household, that’s difficult to achieve. With newly built real estate, you can plan for the gas tankless water heater’s drainage with the condenser beforehand.

Rheem RTGH-95DVLN is a powerful HVAC device that can achieve the maximum hot water flow of 9.5 GPM. That’s enough, even for a larger household. Depending on your location, you can run two showers and a faucet simultaneously, for example.

On top of that, it even surpasses the Japanese standard of a 10-year warranty for the heat exchanger. The Rheem offers a 12-year warranty on the heater exchanger.

For the high energy-efficiency and power, the price of about $1,200 is quite acceptable. Remember that having energy-efficient gas tankless heater will pay for itself in lower natural gas costs.

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#6 American Standard TCWH199S-AS-NG (Surprising EF Rating Of 0.96)

American Standard is a well-known US-based company that makes anything from faucets, toilets to gas tankless water heaters. Their best model – the powerful TCWH199S-AS-NG – has one incredible specification: the EF = 0.96.

That means it uses 96% of the energy generated by burning the natural gas for heating the water. Only 4% of all that energy is lost. That’s even better than the best Rinnai gas tankless heater (#1 pick), which has 0.95 EF. In essence, the American Standard has created the most energy-efficient tankless gas hot water heater.

Why is the TCWH199S-AS-NG model not voted the best tankless gas heater in 2023? In fact, it has quite a bad rap. Where the catch? Well, several people who installed the American Standard TCWH199S-AS-NG complain about temperature fluctuations.

The majority of tankless gas water heaters have an exact mechanism involving just the right amount of natural gas and just the water heating element’s right water flow. This guarantees a continuous flow of hot water at constant water flow and water temperature.

In the case of the American Standard TCWH199S-AS-NG tankless gas heater, something appears to be off, or at least that is something several people have experienced. This does result in the below 3-star rating on Amazon:

As stated before, low NOx emissions are always welcome. In part, they result from the TCWH199S-AS-NG being able to use that high percentage of natural gas for water heating.

For such a powerful device (remember that the capacity of TCWH199S-AS-NG is 11 GPM), the price of the American Standard tankless gas heater is incredibly low. You can get the 199,000 BTU of heating power for less than $1,000. To put it in another perspective, the average price for a 10 GPM gas tankless heater should be about $1,000. Here we have an 11 GPM device for less than $1,000.

Nonetheless, the output hot water temperature fluctuations are the last thing you would want from a tankless water heater.