Best Tankless Gas Water Heater That Are Cost-Effective and Save Energy

Introduction of the Best Tankless Gas Water Heater

Water heaters are designed to make lives easy. If you’re someone who wants an endless supply of hot water without a high electricity bill, then you should consider investing in an efficient tankless gas water heater. By making use of natural gas or liquid propane, these heating machines save energy and drastically reduce your expenses on a monthly basis. Opting for these eco-friendly water heaters means that you’re doing your bit to protect the environment. Check out more for the Best Tankless Gas Water Heater.

We spent a number of hours rigorously testing the different models of tankless water heaters that operate on gas. We created a list of 8 tankless gas water heaters that have been analyzed in terms of their ease of installation, warranty, GPM (gallons per minute) and venting system, among other factors. Choose from a variety of indoor, outdoor, whole house and portable type water heaters to find the perfect one for you and your family.

Tankless Gas Water Heaters Comparison Chart

Rheem RTGH-95DVLN18.5 x 9.8 x 27.5 inches79 pounds12 yearsClick Here for Price
 Rinnai RUC98iN Ultra Series10 x 18.5 x 26 inches82 Pounds12 yearsClick Here for Price
 Takagi T-K4-OS-NG8.5 x 13.8 x 20.3 inches38 pounds5 yearsClick Here for Price
Rinnai V65IN13.9 x 8.8 x 23.6 inches49.6 pounds10 yearsClick Here for Price
Rheem RTG-84XLN14 x 10 x 26 inches54 pounds6 yearsClick Here for Price
Eccotemp i12-LP13.7 x 25 x 5 inches28.9 pounds2 yearsClick Here for Price
Noritz NRC66DVNG6.7 x 13.8 x 23.6 inches39 pounds12 yearsClick Here for Price
Eccotemp L1015 x 6.5 x 35 inches27 pounds1 yearsNo products found.

Tankless Gas Water Heaters

1.Rheem RTGH-95DVLN

Rheem RTGH-95DVLNClick Here for Price

What we liked?

Rheem is a highly trusted brand in terms of creating water heaters that cater to huge households. We’ve kept Rheem RTGH-95DVLN at the top of our list because we consider it to be the best natural gas tankless water heater. With a high flow rate of 9.4 gallons per minute (GPM) and gas input rate of 180,000 BTU’s, this heater will deliver endless hot water without any temperature fluctuations. This means that your entire family can get hot water even when multiple showers and sinks are being used simultaneously.

Since it is an indoor water heater, it is built in a compact manner measuring 18.5 x 9.8 x 27.5 inches and weighing 79 pounds. You can place it inside a closet or in any corner of your house without letting it obstruct your freedom of movement. Along with this, this model features a modern design which we think will easily blend in today’s contemporary homes.

Diving further into the specifications, we discovered that Rheem has crafted this model to be around 94% energy efficient with smart electronic controls that increase its safety. What further heightens its secure functioning is its low NOx feature which means that it emits very low to negligible amount of harmful nitrogen oxide and does not damage your family’s health. A highly efficient stainless steel condensing heat exchanger and digital display for temperature setting and maintenance codes add to the many amazing features of this model.

Modelled for PVC pipe, Rheem RTGH-95DVLN has a 2 pipe direct vent system. You can use either 38 ft. of 3 inch PVC pipe or a 5 ft. of 2 inch PVC pipe. Unlike other models mentioned in this list, you don’t necessarily need a professional to install this water heater. A self-diagnostic system allows for easy installation and service. What’s more is water saving activation technology that reduces flow rate of water in pipes until set temperature of the heater is reached. This could save up to a massive 20,000 gallons of water per year. You also get a remote control to operate your system,  Guardian overheat film wrap (OFW) to avoid damage due to overheating and 10 ft. of thermostat wire.

What we really liked about this model is that its capacity can be increased. This is useful specially when there are guests in your house. An EZ-link cable is available that can connect two tankless units to operate as one. You can manifold up to 20 units with the optional MIC-185 plus the MICS-180 manifold control assembly.

Furthermore, this water heater functions perfectly even in high altitudes up to 9,840 ft. elevation above sea level and has freeze protection at -30 degree F. In addition, Rheem also provides a 120 volt power cord and a recirculation pump kit that helps water to circulate faster before it turns cold. You also get a solid 12 year limited warranty on heat exchanger, 5 year limited warranty on parts and 1 year warranty on labor.

What we didn’t like?

Rheem RTGH-95DVLN requires venting which means you need to figure out extra space preferably through the roof for the exhaust to be blown outside.

Apart from this, the model has a very low kick on rate which means that it starts heating instantly. We found that if faucets aren’t turned to extreme cold, the intensely hot gush of water can be discomforting and can even cause burns.

        Pros        Cons
9.4 GPM
Low NOx feature
EZ-link cable to connect tankless units
Requires venting
Low kick on rate

 2.Rinnai RUC98iN Ultra Series

Rinnai RUC98iN Ultra SeriesClick Here for Price

What we liked?

We have another best-liked model on this list for you.  Rinnai RUC98iN Ultra Series is ideal for large families and has an enormous flow rate of 9.8 GPM which is sufficient for a minimum of two showers and two sinks being operated at the same time. This flow rate stems from the natural gas intake which varies from 15,200 to 199,000 BTU’s (British Thermal Unit). We found that its space saving structure measuring 10 x 18.5 x 26 inches and weighing 82 pounds makes it really easy to be installed indoors.

We highly suggest this model because of its energy star certification. Since it is operated on natural gas or propane, this water heater lowers your electricity bills. With a 0.92 uniform energy factor and ultra-low NOx emissions, Rinnai ensures conservation of energy as well as the welfare of your family. It’s hard to find a tankless gas water heater with energy efficiency as high as this one.

Rinnai RUC98iN operates on 120 volts of electricity and comes with a MC-91-2US controller that lets you set the temperature according to your needs. You can set temperature between the heating range of 98 degree F and 140 degree F.  Along with such amazing features, you get a 12 year warranty on heat exchanger, 5 year warranty on parts and 1 year on labor for water heaters installed for residential purpose. For commercial purpose, you get 5 year warranty on heat exchanger, 5 years on parts and 1 year on labor.

What sets his water heater apart from Rheem’s is the choice of venting. RUC98iN has two venting options: concentric-PVC and twin-pipe. You can select one which you find easy to install and start getting hot water from the heater. To conclude, this model is a long term investment that will yield tax benefits in the long run. You will definitely get returns by reducing energy use for water heating.

What we didn’t like?

Though there are a plethora of features that we really liked in Rinnai RUC98iN, we found its installation problematic. If you opt for professional installation, it can be really expensive costing you up to $3000. But if you choose to install it yourself, it can cost you around $1500. The installation charges coupled with the price you pay for the water heater can be heavy on your pocket.  As a long term investment, it’s still worth the price.

In terms of expenses, the concentric exhaust adds to your bill because additional OEM (Original Equipment Manufacturer) parts need to be shipped resulting in shipping costs as well. Till the time your parts don’t arrive, you will not be able to get any hot water.

        Pros        Cons
9.8 GPM
0.92 uniform energy factor
concentric-PVC and twin-pipe venting options

3.Takagi T-K4-OS-NG

Takagi T-K4-OS-NGClick Here for Price

What we liked?

What if we told you that a much smaller water heater weighing merely 38 pounds can provide you with endless hot water and is also energy efficient? Takagi T-K4-OS-NG makes a strong entry on our list with its flow rate of 8.0 GPM and a gas input capacity of 190,000 BTU’s that is sufficient for tiny homes with limited space. Measuring only 8.5 x 13.8 x 20.3 inches, the ultra-compact design of this outdoor water heater can be mounted on a wall outside your house. Since it is placed externally, there is no buildup of gas inside the house and this ensures a congestion free ambience.

With an energy factor of 0.82, Takagi with its K4 series has made sure that its gas powered models are more efficient and less expensive than electric water heaters. In addition, this model has energy star certification which means it does not harm the environment. Further, low NOx emission safeguards your family’s health. Moreover, this system working on 120 volts of electricity can deliver on demand hot water and can be used in storage tanks, domestic applications, radiant floor systems, hydroponic systems, and recirculation systems.

A unique non-condensing and built-in freeze protection technology does not let water freeze when the temperature outside drops. So even if you live in places where it is extremely cold, this water heater will give you hot water all the time. To avoid supply of water that is not uniformly heated, Takagi has intelligently made use of inlet, outlet thermistors for monitoring temperature constantly. What sets this model apart even further is that it does not require any venting but has a direct vent which measures 4 inches. In terms of warranty, you get 5 years on heat exchanger, 3 years on parts and 1 year on labor. Finally, this model by Takagi is moderately priced and is one of the best outdoor tankless gas water heater.

What we didn’t like?

Takagi T-K4-OS-NG is a complete value package that we found difficult to find faults with. If we do have to mention one, it would be regarding its installation. The warranty of this model is valid only if it is installed by a licensed technician. Installing the unit yourself will cause the warranty to be invalid. Professional installation is not just costly but it is also difficult to find licensed technicians.

Furthermore, this model has electric ignition which means that if there is no electricity and no power backup systems, then you will not get hot water. People living in areas where power outages are common should avoid choosing this water heater.

        Pros        Cons
Lightweight-38 pounds
Built-in freeze protection technology
Installation only by licensed technician
Electric ignition


 4.Rinnai V65IN

Rinnai V65INClick Here for Price

What we liked?

Adding to the list of compact, indoor tankless gas water heaters is Rinnai V65IN measuring 13.9 x 8.8 x 23.6 inches and weighing 49.6 pounds. With a flow rate of 6.5 GPM, it is great for being installed in small to average sized homes. A natural gas or propane input capacity of 150,000 BTU’s and no NOx emissions makes sure that no harmful gases are released inside your house. As a bonus, it is also energy star certified with uniform energy factor of 0.80 which means that it is environment friendly. With a small temperature indicating LCD screen, this model looks simple, and above all solid as well as sturdy.

A unique feature that we found in this water heater is its capability to shut down in case of a home leak detection in order to prevent further damage.  This is highly helpful specially when the residents are unaware of gas leaks and become prone to damage of life and property.

You can easily control your water heater and all its functions with the help of Control-R 2.0 mobile app that can be accessed on your smartphone. This app can be used to set timers and schedules for the entire day. What we found to be a highly convenient feature is that you can put the heating system on vacation mode in case you decide to go on a holiday. In this way, your water heater will stay safe even in your absence.

Rinnai V65IN comes pre-set at 120 degree F and has a temperature range that varies between 98 degree F and 140 degree F which gives you ample choice to set the temperature just right. You can operate this model at 120 volts of electricity. Along with this, V65IN is compatible with Rinnai digital controllers using which you can set different temperatures. In terms of residential factory warranty, you get 10 years on heat exchanger, 1 year on labor and 5 years on parts.

What we didn’t like?

We found a similar drawback as we did in the Takagi K4 series. Rinnai V65IN too, has electric ignition which means that you’ll get hot water as long as you have electricity. In case of a power cut, you’ll have to wait till the electricity is back and let’s be honest, no one likes delays.

        Pros        Cons
Lightweight- 49.6 pounds
Automatic shut down in case of home leak detection
Electric Ignition

  5. Rheem RTG-84XLN

Rheem RTG-84XLNClick Here for Price

What we liked?

Highly compact and minimalistic in design, Rheem RTG-84XLN is an outdoor tankless gas water heater that will save a lot of storage space as it is installed outside your home. Most water heaters have problematic installation as they can be set-up only by professional technicians. Rheem has provided wall mounts that lets you place your water heater on the wall without any hassles. Just refer to the installation guide that comes with the package to install the unit.

Unlike the previous model of Rheem that we mentioned in our list, RTG-84XLN weighs only 54 pounds and measures 14 x 10 x 26 inches. Operating on 120 volts of electricity, this water heater has a maximum natural gas input of 1,80,000 BTU’s.  Along with this, this model is also a low NOx version and energy star certified which means that by choosing this water heater, you’re doing your bit to save the environment. An impressive flow rate of 8.4 GPM at 35 degree rise can provide unlimited hot water supply to 3 bathrooms simultaneously which is ideal for an average household size. We found out that it is one of the highest volume tankless water heaters.

In addition, you also get 10 ft. of thermostat and a UMC-117 remote control with which you can set and control temperatures at all levels. Unique Next Generation Burner technology heats water efficiently in no time and saves a lot of money on your electricity expenses.

On its heat exchanger, Rheem gives you a warranty varying from 6 years to as long as you own the home in which the unit is installed. You also get a warranty that varies from 1 to 10 years on the parts of the model.  To conclude, if you’re planning to switch from a tanked water heater to tankless one that belongs to a trusted brand and is economical, then we recommend Rheem RTG-84XLN.

What we didn’t like?

When we compared Rheem RTG-84XLN to other similarly priced models, we discovered that its natural gas requirement was higher than others. So what you save on your electricity bill might be compensated by the high natural gas intake. Apart from this, it is also heavier than other models in the same price range.

        Pros        Cons
Easy installation
High natural gas intake

 6. Eccotemp i12-LP

Eccotemp i12-LPClick Here for Price

What we liked?

We have added the Eccotemp i12-LP to our list for everyone who’s looking for an indoor tankless gas water heater under $500. With a flow rate of 4 GPM and 11.36 LPM (Liters Per Minute), this water heater is suitable for a small to average household. We liked its feature of being activated on demand. Also, the absence of pilot light consecutively reduces energy consumption.

What really stood out for us was its revolutionary design of sleek, black tempered glass front panels which are equipped with LED display controls that are convenient to use. Being the second lightest water heater on our list with a weight of 28.9 pounds, it is also compact measuring 13.7 x 25 x 5 inches. Along with this, the temperature controls are fully automatic with special energy saving mode and child lock technology. So your unit stays safe from being tampered by kids.

Eccotemp i12-LP needs a 110 volt electrical outlet with VL-listed cord and standard ½” NPT water fittings to operate. Easy installation with wall mounts coupled with horizontal venting makes this model a good buy. With a gas rate range of 25,000 to 80,000 BTU’s, you can use this electrically ignited water heater in small households. Eccotemp i12-LP can power two faucets on full flow. Plus it is highly budget friendly as it is propane powered.

In terms of warranty, you get a 2 year limited manufacturer warranty on the parts. Eccotemp is known for their great customer support and upgradation of models based on feedback. So feel free to get in touch with them in case you have any queries.

What we didn’t like?

Since Eccotemp i12-LP can power only two faucets at a time, it is not ideal for an entire household that needs hot water supply in multiple outlets. Along with this, an exhaust vent is needed that leads directly to the outside for the residual gas to escape.

        Pros        Cons
 Stylish tempered glass front panels
Easy to install
Entire household cannot be supplied with hot water at one time
Exhaust vent needed

 7.Noritz NRC66DVNG

Noritz NRC66DVNGClick Here for Price

What we liked?

Noritz NRC66DVNG is a high quality condensing indoor water heater that is powered by natural gas. Along with this, it is also energy star certified with low NOx emission. It is 93% efficient for use with natural gas or propane and has an energy factor of 0.91. So it qualifies for being an eco-friendly water heater that you should consider if you’re not looking for a model that’s too cheap.

In terms of venting, you can use a 3”Schedule 40 and 80 PVC pipe and fitting which are easily available in hardware stores. The direct vent (DV) model can also be converted to a non-direct vent (SV) model with the use of a Conversion Kit. So the process of installation becomes convenient and can be completed even without the help of a licensed technician. You don’t require a high temperature vent for this unit.

What’s more is a 6’ power cord and a remote thermostat which will let you set the temperature according to your needs and built in display that can preset the output temperature to either 120°F, 135°F, or 140°F. In terms of built, the Noritz NRC66DVNG weighs just 39 pounds and measures  6.7 x 13.8 x 23.6 inches.

With a flow rate of 6.6 GPM and gas input of 1,20,000 BTU’s, this water heater can still supply hot water to two separate bathrooms, which we think will be ideal for small homes. You can also choose from stainless steel and copper heat exchangers, both of which are resistant to corrosion. In addition, there is a durable steel casing with polyester coating to add to the durability.

Additional features that we discovered while testing this model are Flame Sensor and Overheat Prevention Device Lightning that will alert you every time the water heater gets undesirably hot. Freeze Protection keeps the water hot even when the temperature outside falls extremely low.  High Elevation Adjustment ensures proper functioning even when your water heater is at a considerably high altitude.

Noritz provides a warranty of 12 years on heat exchanger, 5 years on parts and 1 year on labor.

What we didn’t like?

We consider Noritz NRC66DVNG to be an overall package in terms of being efficient in supplying endless hot water. On the downside, we think it might be a little expensive. Considering the fact that its flow rate is quite less, you might look for other models from Rheem or Rinnai with a higher flow rate. This being said, we still think that investing in this model will yield benefits in the long run because of its feature-packed built.

        Pros        Cons
High Energy factor of 0.91
Easy installation

8. Eccotemp L10

No products found.No products found.

What we liked?

Being the lightest water heater on our list with a weight of 27 pounds, Eccotemp L10 is highly portable and perfect for your adventurous camping trips. We found this model to be highly powerful for its small size which measures 15 x 6.5 x 35 inches. This is the only model on our list that serves both as a stationary and as a portable water heater which can function at an elevation of up to 5500 ft. above sea level.

Not only is it lighter than Eccotemp i12-LP but also crafted differently to be used outdoors. It features a 9’ CSA (Canadian Standards Association) approved gas regulator and a hose to be used on a standard 20 lb. grill style tank. With a stainless steel rain cap, you can be assured that this model is highly durable. Along with this, Eccotemp provides a ½” NPT to garden hose adapter, gas regulator and showerhead. All these accessories are perfect for outdoor showers that you can enjoy while on a vacation.

Powered by liquid propane with an intake of 74,500 BTU’s, we figured that this model operates on batteries so don’t forget to carry a spare when you go camping. A 20 minute automatic safety shut off timer is already installed in the system in order to avoid wastage of electricity. Once the water is hot, the heater will shut off automatically, so you need not worry even if you forget to switch it off.

Convenience in all aspects is a bumper feature of this model and that’s why installing it is a piece of cake. All you have to do is mount it wherever you please. In terms of flow rate, 3 GPM is sufficient to supply hot water to one household faucet at a time.

In terms of warranty, you get a 1 year warranty on the heater.

What we didn’t like?

Eccotemp L10 has been crafted to cater to outdoor activities like camping trips. Its function is quite limited when used indoors as it can power only one faucet at a time. Apart from this, there is no visual thermostat to check the current water temperature.

        Pros        Cons
Highly portable
Automatic safety shut off
When installed indoors, can run only one faucet at a time
No visual thermostat

 Tankless vs. Traditional Water Heaters

Tankless Water HeaterTraditional Water Heater (with storage tank)
  • Heats water only when you need it and do not incur standby energy losses.
  • Mounts on a wall and saves floor space.
  • More expensive to buy with installation charges up to $2000.
  • Lasts more than 20 years and is a long term investment.
  •  Continuously heats water and keeps it stored in the tank. You pay for hot water even when you don’t need it.
  • Takes up space when placed in the basement or a closet.
  • Cheaper to buy with installation charges less than $900.
  • Shorter life span and needs to be bought twice as often as a tankless water heater.
1. How do I choose a tankless gas water heater?

Tankless gas water heaters are a one-time investment that pays off in the long run. So if you’ve made up your mind to buy one then you should consider analyzing these top 3 factors before you go shopping.

  • Flow Rate Depending on the size of your household and the consumption of hot water, decide on the flow rate that suits your needs. Flow rate is measured in gallons per minute or GPM.  A water heater like Rheem RTGH-95DVLN, having a GPM of 9.4 is sufficient for supplying endless hot water to more than two bathrooms and two sinks simultaneously.
  • Types Tankless gas water heaterscome in both indoor and outdoor types. If you have space to spare in your house, then you can choose an indoor one which can be mounted on a wall or placed in a cabinet. There is always a potential drawback of gas build-up inside the house with indoor water heaters if venting is not done properly.

Outdoor water heaters do not provide hindrance in daily activities as they are placed outside the house. But there is always a possibility of them becoming more worn out with time when compared to indoor water heaters.

  • Venting Gas water heaters have two venting methods: direct-vent and power-vent. Two types of direct vent units exist- intake and exhaust vents. The mechanism of intake vents is such that air is drawn from outside the house via the ventilation pipe and hot exhaust exits through a different pipe. Direct vent units are suitable to be installed in places which lack space.  Power-vent water heaters make use of the air around them and have only one ventilation pipe for exhaust. If the location does not have fresh air around, then it is wise to convert to a direct-venting system.
2. Is a tankless gas water heater worth it?

Buying a tankless gas water heater might be expensive along with the professional installation that most models require. Once installed, these heaters will serve you for more than 20 years and being highly energy efficient, they will also reduce your electricity bills. You will also be doing your bit for the environment as these heaters are eco-friendly.. Being economical, eco-friendly and durable, we believe tankless gas water heaters are totally worth their price.

3. How many gallons per minute (GPM) does a tankless gas water heater deliver?

Tankless gas water heaters deliver in the range of 4-9 gallons per minute. If you need hot water only in one sink and one shower at a time, then 4-5GPM is suitable. But if your requirements are higher like multiple showers, sinks and washers then opt for 8-9 GPM flow rate.

4. What are the advantages and disadvantages of a tankless gas water heater?

A tankless gas water heater has the benefits of being eco-friendly, energy efficient and cost effective in the long run. In the short run, it is expensive in terms of its parts and the installation process.

5. Can a tankless gas water heater fill a tub?

Yes, tankless gas water heaters will provide hot water and fill your tub for as long as its switch is not turned off.

6. How much gas does a tankless gas water heater use?

Natural gas intake varies for different models of water heaters. For example, Rheem’s water heaters with flow rates in between 8-9 GPM need an input of 180,000-199,000 BTU’s (British Thermal Units). Water heaters with lower flow rates like 4 GPM need 25,000-80,000 BTU’s.

8. How do I adjust the temperature on my tankless gas water heater?

Tankless gas water heaters come with a built-in LED display panel. This panel offers controls that can be used to regulate temperature precisely by each degree which is so much more efficient than an old-school dial regulator. You can also set different temperatures for different devices. As part of your computerized temperature controls, you can choose from fan settings that let you control the temperature. Some brands like Rinnai go one step ahead and offer remote controls to set temperature according to your needs.

9. How does a tankless gas hot water heater work?

When you open a hot water tap, a sensor connected to the ECU detects the flow. Right after this, the heating process begins. Some models have combustion fans that pull in air for the process of combustion. ECU starts the flow of gas and triggers the igniter. The igniter sparks until the flame sensor detects a flame. In case the flow through hot water heater fails to light within a few seconds, the ECU shuts down the gas flow to prevent any unsafe accumulation of gas.

10. Will Tankless Gas Water Heaters Replace Traditional Water Heaters?

There is a high possibility that tankless gas water heaters might altogether replace traditional water heaters. Tankless heaters are portable, save space, protect the environment and even lower the electricity bill. Traditional water heaters on the other hand are cheaper to buy but need to be replaced frequently than tankless heaters. In addition, storage tanks take up a lot of space.

11. Does tankless gas hot water heater need electricity?

If a tankless gas water heater has electric ignition, then it needs electricity to operate.

12. Is it cheaper to use electric heaters or gas?

Natural gas is significantly cheaper than electricity and that’s why it is cheaper to use gas water heaters.

13. How often should tankless gas water heaters be serviced?

Gas water heaters generally require less maintenance than electric water heaters. But at some point, gas heaters are bound to develop issues. Instead of waiting for 2-3 years for a major problem to crop up that increases your expenses considerably, try going for a preventive maintenance check-up at least once a year. In this way, your heater will not just operate better but also last longer.


We have listed down a plethora of tankless gas water heaters that cater to varied needs of different households. Considering all factors that are required for a good tankless water heater, we personally recommend Rheem RTGH-95DVLN and Rinnai RUC98iN Ultra Series.

Apart from being models of highly trusted brands, these water heaters will serve you with their high flow rates and even higher warranty periods for years to come. If you have an adventurous soul, then we suggest you opt for Eccotemp L10 with its stylish, portable body that will be perfect for outdoor showers.

We hope our guide to knowing all about water heaters was helpful to you. Now, it’s time for you to decide which one suits your needs best.


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Last update on 2024-02-20 / Affiliate links / Images from Amazon Product Advertising API

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