6 Best Gas Tankless Water Heaters (Reviews & Buying Guide 2020)


A tankless water heater is not only a space saver, but it can also save you money on utility bills while ensuring endless hot water supply. Are you wondering which is the best gas tankless water heater out there? For your convenience, you can choose between two options for gas heaters. The first one is propane, which may be more convenient, while the alternative is natural gas, which also comes with an array of potential benefits.

If you want to take your water heating to the next level, you undoubtedly need a tankless heater. It doesn’t require a storage tank, which means it doesn’t store hot water. Instead, it heats it while it passes through the unit. That enables it to save space and energy while ensuring optimal hot water temperature!

Take a look at our selection of tankless gas water heater reviews. Please note that we’ve reviewed these gas tankless water heaters according to their fuel types; Natural Gas and Propane. Regardless of your preferred choice of fuel for the unit, you might find one that fits your needs. Make sure to check out our detailed buying guide to know what features to look for in a tankless heater.

  • 4.2 Customer Rating
  • RINNAI V75IN Indoor Natural Gas Tankless Water Heater
  • PRICE $$$$
  • Dimensions: 14 x 9 x 23"
  • Weight : 68 lb.
  • Max Flow Rate: 7.5 GPM
  • Energy Factor : 0.82
  • Warranty : 12 Years
  • 4.1 Customer Rating
  • RHEEM RTG-84XLN Outdoor Natural Gas Tankless Heater
  • PRICE $$$$
  • Dimensions: 14 x 10 x 26"
  • Weight : 54 lb.
  • Max Flow Rate: 8.4 GPM
  • Energy Factor : 0.81
  • Warranty : 2 Years
  • 4.1 Customer Rating
  • TAKAGI T-KJR2-OS-NG Outdoor Natural Gas Tankless Water Heater
  • PRICE $$$
  • Dimensions: 6.7 x 14 x 21"
  • Weight : 38 lb.
  • Max Flow Rate: 6.6 GPM
  • Energy Factor : 0.82
  • Warranty : 15 Years
  • 4.3 Customer Rating
  • Bosch 940 ES NG Indoor Natural Gas Tankless Water Heater
  • PRICE $$
  • Dimensions: 12 x 18 x 31"
  • Weight : 67 lb.
  • Max Flow Rate: 9.4 GPM
  • Energy Factor : 0.95
  • Warranty : 3 Years
  • 4.1 Customer Rating
  • NORITZ NRC661-DV-NG Indoor Natural Gas Tankless Water Heater
  • PRICE $$$$
  • Dimensions: 7 x 14 x 24"
  • Weight : 41 lb.
  • Max Flow Rate: 6.6 GPM
  • Energy Factor : 0.89
  • Warranty : 12 Years
  • 4.3 Customer Rating
  • Eccotemp i12-NG Indoor Natural Gas Tankless Water Heater
  • PRICE $$
  • Dimensions: 16 x 16 x 11"
  • Weight : 29 lb.
  • Max Flow Rate: 3 GPM
  • Energy Factor : 0.81
  • Warranty : 3 Years

Best Natural Gas Tankless Water Heater Reviews

1. Rinnai V75IN Indoor Natural Gas Tankless Water Heater

Rinnai-V75IN-7.5-GPM-Indoor-Low-NOx-Tankless-Natural-Gas-Water-HeaterIf you have a mobile home, you may want to consider this unit as it has the necessary installation certificate. The manufacturer designed the heater for indoor installation, and it is also compliant with SCAQMD, which means it has extra-lower emission of NOx.

Maximum power of Rinnai V75IN is 180,000 BTUs, making it suitable for the most residential home. Its energy factor is 0.82 whether you use propane or natural gas. The unit can deliver hot water varying from 98F to 140F in temperature. You get a controller with the model, as well as the leak detection feature to limit damage in case of mishaps.

As long as you handle the installation properly, there should be no problem with the water pressure. The overall dimensions of the unit are 14 x 9 x 23 ounces. The installation is not too difficult, and you may even consider handling it yourself.
For more detail, see our full review of Rinnai V75IN

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2. Rheem RTG-84XLN Outdoor Natural Gas Tankless Water Heater

Rheem-RTG-84XLN-Outdoor-Tankless-Natural-Gas-Water-HeaterThis is one of the units you may consider if you are looking for an outdoor NG water heater. The manufacturer designed it for outside installation, but they also ensured to include a thermostat and a remote for effortless control of the heater’s performance. The remote can provide hot water with a temperature of up to 140F. You can adjust the settings with the remote in five-degree increments. It is interesting, however, that this increment is missing between 130F and 140F, but that shouldn’t be a problem to find the optimal temperature of water.

With 180,000 BTUs of power and 8.4 gallons per minute flow rate, this unit is quite powerful. However, the maximum flow rate is available at a 35-degree increase and may vary if you need a higher temperature rise. Regardless, it should cover two or more simultaneous faucets without any problems.
For more detail, see our full review of Rheem RTG-84XLN

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3. Takagi T-KJr2-OS-NG Outdoor Natural Gas Tankless Water Heater

The manufacturer indicates that this is one of the smallest models in their lineup. As a result, it is primarily intended for residential use. Keep in mind that the unit requires an outdoor installation. Its measurements are 20.5 x 13.8 x 6.7 inches, but a couple of inches of extra space should be allowed below the unit for connections to the water and gas lines. The model also comes with a feature that enables protection from the internal freeze.

The specification sheet indicates that the model’s energy factor is 0.79 and it can deliver BTU anywhere from 19,500 to 140,000 BTUs. Although it might not matter that much for an outdoor unit, you will be glad to know that it is quiet when in operation. The model’s flow rate is a maximum of 6.6 GPM, but its actual performance may vary depending on the heat rise you are seeking.
For more detail, see our full review of Takagi T-KJr2-OS-NG

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4. Bosch 940 ES NG Indoor Natural Gas Tankless Water Heater

Bosch 940 ES NG Natural Gas Tankless Water HeaterIf your goal is to heat multiple appliances with a single tankless water heater, you should consider this model. It is the highest capacity unit made by Bosch which has the goal of meeting the expectations of big household.
The heater can deliver 9.4 gallons of water per minute measured at a degree rise of 35F. It should be enough to never risk running out of hot water even if two or three units are running simultaneously.

The maximum input of this non-condensing unit is 199,000 BTUs. The product utilizes an electronic ignition, sealed combustion, and dual-fan technology. That makes the heater a huge space saver and suitable to install anywhere.
The measurements of the unit are 12 x 18 x 31 inches while the weight is 67 pounds. If you want to install the heater outdoor, you will need a matching vent kit. The good news is that the installation process is fairly easy.

For more detail, see our full review of Bosch Therm 940 ES

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5. Noritz NRC661-DV-NG Indoor Natural Gas Tankless Water Heater

Noritz-NRC661-DV-NG-Pros-ConsThe unit has three different preset temperature settings with the maximum one being 140F. The temperature rise can be up to 70 degrees means you can consider Noritz NRC661 for both cold and warm climates. Its flow rate is set at maximum 6.6 gallons per minute, but the manufacturer lists it can serve two bathrooms at southern climates and 1.5 at northern conditions.

The energy factor of the natural gas unit is 0.91. Keep in mind that this condensing unit doesn’t come with venting pipes, but PVC pipes are suitable, so you shouldn’t have any problem with the installation. The model has the SCAQMD certification to ensure low emission of NOx. The material used to make the casing is durable steel while the coating is of polyester. The unit comes with 5-year parts warranty and 12-year heat exchanger warranty if used in residential properties.
For more detail, see our full review of Noritz NRC661-DV-NG

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6. Eccotemp i12-NG Indoor Natural Gas Tankless Water Heater

Eccotemp i12 Natural Gas Indoor Tankless Water HeaterThe first thing that you notice with this unit is its design with the black color dominating. Next, you focus on the LED display on the front. The touchscreen display is not only pretty but also simple to use to adjust the temperature. When the temp drops below freezing, however, make sure to drain and disconnect the unit. Eccotemp i12-NG is suitable for indoor installation.

The manufacturer provides a 2-year limited warranty on the product. The overall measurements are 16 x 16 x 11 inches. As for the flow rate, it is at optimum 3GPM at a 40degree rise. While its flow rate may decrease a bit if the required temperature rise is higher, it can heat the water up to 80 degrees and still provide adequate flow. The factory testing confirmed you could use the unit at up to 5,500 feet of altitude.
For more detail, see our full review of Eccotemp i12-NG

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7. Takagi T-K4-IN-NG Indoor Natural Gas Tankless Water Heater

Takagi TK4 Indoor Natural Gas Water HeaterAlthough the first unit was made in 2010, this unit is still a smart choice for many homeowners out there. Its power input varies from 11,000 to 190,000BTUs while the manufacturer mentions 8.0GPM as the maximum flow rate. These specifications indicate that this unit can cover two to three bathrooms depending on the bathroom size and the installation location.

The overall measurements of the Takagi T-K4 are 20.3 x 13.8 x 8.5 inches. It has the option of direct venting, as well as an energy factor of 0.82. The manufacturer indicates that the temperature of the heated water may vary from 99 to 167F. The unit comes with a wired remote that is approximately 20 inches long.

The manufacturer designed the model for indoor use, and the installation is semi-difficult. It may take a bit of time for the hot water to travel to the faucet, but the rise in temperature makes the wait worth the time.
For more detail, see our full review of Takagi T-K4-IN-NG

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8. Rinnai V75EN Outdoor Natural Gas Tankless Water Heater

Rinnai-V75EN-7.5-GPM-Outdoor-Low-NOx-Tankless-Water-HeaterAt first glance, it seems that Rinnai V75En has all the features that an outdoor heater requires. Its power goes up to 180,000BTUs, which secures temperature rise optimal to get the water up to 140F. If you want to optimize energy savings, there is a controller available, too. It makes it possible to choose between several temperature levels from 98F to 140F.

The maximum flow rate is 5.3 gallons per minute, which is a bit less compared to some other similar units. However, keep in mind that this is a compact unit not meant for large homes. In fact, it has a mobile home certificate. It is also environmental-friendly since its NOx emission is low and its energy factor is 0.82. The unit comes with a scale and leaks detection features that can prevent serious damage to the model and the property.

For more detail, see our full review of Rinnai V75EN

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9. Rheem RTGH-95DVLN Natural Gas Tankless Water Heater

Rheem-RTGH-95DVLN-Tankless-Natural-Gas-Water-HeaterThe Rheem RTGH-95DVLN 9.5 Indoor Direct Vent tankless natural gas water heater has a lot going for it. At 9.5 gallons per minute, it is one of the highest volume natural gas water heaters on the market. Not only can it provide adequate supply to serve a large household, but it also does an excellent job of keeping the water temperature constant even during heavy water usage.

Rheem RTGH-95DVLN 9.5 come with advanced energy features and high volume capacity. Despite its ability to produce a high volume of hot water, it has a 96 percent energy rating, making it extremely energy efficient.

Rheem RTGH-95DVLN 9.5 also has proprietary water saving activation technology that can help you save 1,100 gallons of water each year. It also comes with a recirculation pump that helps maintain the water temperature and reduces the loss of water during low demands.

This water tank has an impressive feature that allows you to control it remotely via a mobile app. You only need to buy the necessary accessory, and you can start monitoring it from your phone.

Besides, Rheem RTGH-95DVLN 9.5 comes with a 12-year manufacturer’s warranty. While it weighs 82 pounds, this unit is unarguably one of the top tankless water heaters you can find on the market. It can work at -30 degrees Fahrenheit, making it perfect for use in the high mountains or cold environments.
Read the full review: Rheem RTGH-95DVLN

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10. Rinnai V65IN 6.6 GPM Natural Gas Tankless Water Heater

Rinnai-V65IN-Tankless-Natural-Gas-Water-HeaterThe Rinnai V65IN indoor tankless water heater is an innovative product from Rinnai. This manufacturer was able to churn out a compact device that weighs 0.32 ounces and measures 13.9 x 8.8 x 23.6 inches. With this size, you are at liberty to mount it at any location in your house, office or even salon. It leaves plenty of space while at the same tie it ensures that your hot water needs are met. Its great performance is exhibited through the 6 GPM rating which is quite impressive. This gives you and your family enough of hot water.

The low Nox Technology is also present which ensures that the emissions are minimized. Rinnai also ensured that the material used in the manufacturer of this device is heavy-duty making it durable. The installation and maintenance practices are minimal making the product a perfect choice for all ages. Various warranty policies also apply, and this makes this product top notch.
Read the full review: Rinnai V65IN

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  • 3.8 Customer Rating
  • ECCOTEMP I12-LP Indoor Liquid Propane Tankless Water Heater
  • PRICE $$$
  • Dimensions: 15 x 24 x 4"
  • Weight : 29 lb.
  • Max Flow Rate: 3 GPM
  • Warranty : 2 Years
  • 4.0 Customer Rating
  • GASLAND BE158 Portable Propane Tankless Water Heater
  • PRICE $
  • Dimensions: 12 x 6 x 17 "
  • Weight : 15 lb.
  • Max Flow Rate: 1.6 GPM
  • Warranty : 1 Years
  • 4.1 Customer Rating
  • VEVOR Indoor Propane Tankless Hot Water Heater
  • PRICE $
  • Dimensions: 28 x 16 x 8"
  • Weight : 22 lb.
  • Max Flow Rate: 4.8 GPM
  • Warranty : 1 Years
  • 4.7 Customer Rating
  • RHEEM RTG-95XLP Outdoor Propane Tankless Water Heater
  • PRICE $$$$
  • Dimensions: 14 x 10 x 26"
  • Weight : 54 lb.
  • Max Flow Rate: 9.5 GPM
  • Warranty : 1 Years
  • 4.1 Customer Rating
  • RINNAI V65EP Outdoor Propane Tankless Water Heater
  • PRICE $$$$
  • Dimensions: 9 x 14 x 23"
  • Weight : 60 lb.
  • Max Flow Rate: 6.6 GPM
  • Warranty : 5 Years
  • 4.1 Customer Rating
  • Eccotemp L10 Propane Portable Tankless Water Heater
  • PRICE $
  • Dimensions: 26 x 14 x 8"
  • Weight : 27 lb.
  • Max Flow Rate: 2.6 GPM
  • Warranty : 1 Years

Propane Tankless Water Heater Reviews

1. Eccotemp i12-LP Indoor Liquid Propane Tankless Water Heater

Eccotemp-i12-LP-Liquid-Propane-Indoor-Tankless-Water-HeaterThis unit comes in two versions – liquid propane and natural one. We already covered the latter, and the LP version is similar when it comes to aesthetics and performance. It stands out with its sleek design, which makes it a fine fit for modern residential properties. This is particularly important since it requires indoor installation and you can make it look like it increases the aesthetic value of the room.

As for the performance, expect 3GPM flow rate at an optimal temperature rise. The power of the unit varies from 25,000 to 80,000 BTUs depending on the settings. The unit uses electronic ignition and also includes horizontal venting. You will find LED display on the front, which you can use for temperature control. There is a child lock feature, as well as an energy-saving setting. The manufacturer indicates the unit is suitable for small homes, cottages, and cabins.

For more detail, see our full review of Eccotemp i12-LP

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2. Gasland BE158 Outdoor Portable Propane Gas Water Heater

Gasland-BE158-1.58GPM-6L-Outdoor-Portable-Propane-GasIf you are looking for a compact outdoor gas heater, this is a unit worth taking into consideration. It is a small model that belongs to the category of portable heaters. Therefore the product is suitable for RVs, camping, and other on the go needs. Outdoor showers are also feasible with this unit. You have the option of choosing between two color options – classic white one and silver.

It can deliver on-demand hot water with up to 41,000 BTUs of power. Since it is a compact unit, its moderate 1.58GPM was expected. It overcomes that with a simple installation process and is also lightweight. The product runs on D cell batteries, which means that it doesn’t require electricity, but you need to connect it to a propane tank. Although the unit comes with a 1-year limited warranty, it is still a value deal and delivers plenty for the price.

For more detail, see our full review of Gasland BE158

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3. VEVOR 18 L Propane Tankless Hot Water Heater

VEVOR-18L-Propane-Water-Heater-ReviewThis unit is another compact solution for water heating. Its overall measurements are 29.5 x 16.5 x 8.7 inches, and the capacity is set at 18 liters. Keep in mind that the model is only suitable to use with propane. Therefore, you cannot convert it to natural gas. VEVOR 18L features both warm and cold-water protection as the unit will automatically turn off at over 75C. It will also automatically reduce pressure in case it gets excessively high.

The thermal efficiency is at least 80.8%, and you can power the unit with batteries, which you need to buy separately. The product comes with a shower kit and user manual, and it is fairly simple to install. The material used in manufacturing is of adequate quality considering the fact that this is one of the affordable entry-level units. Although the installation process is straightforward, you may want to hire a professional if you do not have prior heater experience

For more detail, see our full review of VEVOR 18L Propane

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4. Rheem RTG-95XLP Outdoor Propane Tankless Water Heater

Rheem-RTG-95XLP-9.5-GPM-Outdoor-Tankless-PropaneAlthough you will place this heater outdoor, it is still vital that it has low NOx emission. It is a guarantee that the unit is environmentally friendly. Rheem RTG-85XLP solely runs on liquid propane and is not suitable for indoor use. It can maintain 9.5 gallons per minute flow rate at a 35-degree rise of the water temperature. Although the GPM may somewhat decrease for higher temperature rise, the chances are you will still be satisfied with the flow rate. For example, you can expect 7.4 GPM at a 45-degree rise, which is still quite good, especially when compared to similar units.

The unit comes with a thermostat and remote control so that you can easily pick the desired temperature of the water. The fact that you can mount it outdoor is an important space saver, especially if you use it in your RV or confined space.
Read on and check out the best RV tankless water heaters.

For more detail, see our full review of Rheem RTG-95XLP

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5. Rinnai V65EP Outdoor Propane Tankless Water Heater

Rinnai-V65EP-6.6-GPM-Outdoor-Low-NOx-Tankless-Propane-Water-HeaterThe energy factor of 0.82 is at an average for gas-powered heater units. Aside from being quite efficient, this unit is compliant with NOx emission regulations. It is also suitable for mobile homes as it has the necessary certificate for installation in those properties. You can lock the temperature to avoid sudden changes in water temperature.

Rinnai V65EP has a maximum power set at 150,000BTUs. Combined with 6.6 GPM maximum flow rate, it allows you to use a couple of appliances simultaneously. For a unit that packs such power, it is quite compact with the size being 9 x 14 x 23 inches. The durability of the unit is expanded by the fact that scale detection is improved. Therefore helping to avoid long-term damages. The unit will require a 120V outlet to function.

For more detail, see our full review of Rinnai V65EP

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7. Camplux 5L 1.32gpm Portable Propane Tankless Water Heater

Camplux-5L-1.32-GPM-Outdoor-Portable-Propane-Tankless-Water-HeaterIf you are thinking about purchasing this heater, keep in mind that you can choose between a single unit and multiple unit bundles. The more you purchase, the more significant the discount you get. As for the specifics, Camplux 5L is a small outdoor propane water heater. Also, it is extremely lightweight with 11.4 x 4.33 x 14.8 inches in size and approximately 14 pounds in weight.

The heater uses batteries to run and has a flow rate of 1.32GPM. As long as the temperature rise is up to 46.4, you should maintain this flow rate without a problem. The unit comes with protection against freezing and overheating and even has a shut-off valve in case of oxygen depletion. The unit comes with a shower attachment, and you can use it until 6,000ft of height. The quality of craftsmanship and durability are solid considering that it is a compact portable heater.

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What Is a Gas Tankless Water Heater?

best gas tankless water heaterA tankless gas water heater is a type of heater that operates on gas and doesn’t require the tank to heat water. In the past, most properties used water storage tanks that would keep a specific amount of water heated around the clock.

Tankless heaters appear with advanced technology as an innovative solution to heating water. They do not store hot water or need a tank. Instead, they can provide endless hot water supply as they heat the water while you are using it.

How Does a Gas Tankless Water Heater Work?

Here is an example of how a tankless heater works – everything starts by you opening a faucet. That is the sign for a water heating unit to start working. The gas burners begin doing their magic and heat the water as it goes through the pipes. That is how you can instantly heat the water. The time required to get hot water depends on the time required for it to travel from its installation point to the faucet.

As soon as you turn off the faucet, the heating unit also shuts down. That means tankless water heaters can save you a significant amount of cash spent on heating. Depending on the specifics of your home or commercial property, these savings can be anywhere from 5% to an impressive 70%. This advantage primarily comes from the fact that the heating unit doesn’t store hot water. Which as a result, means it doesn’t have to be on constantly.

Benefits of Gas Tankless Hot Water Heaters

Although electricity is also an option to power your heating unit, gas is the most popular option for tankless water heaters. Whether you go with propane or natural gas options, you will secure efficient and instant water heating. Read on to see the best electric tankless water heaters on the market today.

Saving money is not the only benefit that the tankless units deliver. They are also environment-friendly since the energy spent is considerably less than with a classic model. Additionally, most tankless units are recyclable, which is another way of contributing to the environment.

Gas tankless water heaters are space savers. The fact they do not require a tank for storing water enables this. You can hang it on the wall, place it behind the stairs, or choose the desired location so that it has an optimal balance between aesthetic value and functionality. Tankless heaters are also a convenient fit for compact homes where each square foot matters.

Gas and electric tankless units each have comparative advantages and disadvantages. This guide will help you weigh the pros and cons of buying a gas vs. electric tankless water heater.

Gas Tankless Water Heater Buying Guide

gas-tankless-water-heater-reviewsAre you planning on purchasing a gas tankless water heater? Before we dig into specifications in details, here is a quick overview of the factors you should take into consideration:

What to Consider When Buying the Best Gas Tankless Water Heater?

  • Power input
  • Flow rate
  • Venting
  • Energy factor
  1. Power Input

    When it comes to tankless water heaters, size and power go hand in hand. You will need a heating unit of the appropriate size to ensure sufficient hot water. At the same time, you require a model powerful enough to increase water temperature effectively. That is how you can be certain that the heat level of the water will always satisfy your expectations.

    The general rule of thumb for the power of these units is the more, the better. While you do not want to waste money on purchasing an unnecessarily large model, you also want to ensure that it has enough BTUs to heat the entire property. The BTU marks the heating unit’s power, and it varies from 10,000 BTUs for small spaces up to 1,000,000 BTUs for large (commercial) properties.

  2. Flow Rate

    Another crucial consideration when picking a tankless heater unit. While power is in charge of securing the right temperature, the flow rate determines the amount of water the model can deliver. You should choose the desired flow rate depending on the number of devices you want the unit to serve. If you only equip a faucet with a tankless gas heater, 1.0 GPM may be enough. However, if you need it to spread across a couple of showers and kitchen sinks, you will require far more than that. Take a look at our sizing guide to choose the optimal flow rate.

  3. Venting

    Venting is crucial for every indoor gas tankless water heater. It ensures that the hazardous gasses are eliminated and removed from the property. The other task of the venting system is to secure additional air intake from the outside if necessary. There are two different venting options to pick from:

    • Direct venting – it contains both exhaust and intake pipes. The former is in charge of getting if of carbon monoxide and other hazardous gasses while the latter ensures sufficient air intake.
    • Power venting – these only require an exhaust pipe. Before installing them, make sure there is enough fresh air coming to the installation area.
      Check the tips here: Tankless Water Heater Venting
  4. Energy Factor

    Energy factor can help you calculate the energy efficiency of a particular unit. In other words, it will tell you more about the average cost of operation. Here is the equation you can use:
    Annual Operation Cost = Fuel Cost X 41045 X 365 / (Energy Factor x 100,000)
    Most of the units have energy factors listed in the product description.
    Trying to find the most energy-efficient water heater? Read this roundup of our recommendations.

Other Features to Consider

gas-tankless-water-heaters-carbon-emissionsNow that you know the most important specifications for a gas tankless water heater, here are some additional features that may help:

  • Reputable brand – if you want your heater to last for a long time, go with a premium brand.
  • Warranty – it is an excellent indicator of how much the manufacturer trusts their product.
  • Certifications – do you need to install the unit in a mobile home? Or you need to ensure that the emission of dangerous gasses is by the restrictions?
  • Thermostat and remote control – both can come in handy to optimize water temperature.

Gas Tankless Water Heater Sizing

The crucial consideration when picking a gas tankless water heater should be its size. The right unit will secure maximum efficiency while ensuring you do not spend a cent more on the heater, installation, or usage. There are two things to keep in mind – temperature rise and flow rate. Before we continue, remember that you should never undermine the required size of a water heater.natural-gas-tankless-water-heater-sizing

How to Select the Right Size Tankless Water Heater

Now, let’s take a look at the process of determining the right sizing of your unit:

  • The number of devices it will cover

    Showers, tubs, kitchen sinks, and even dishwashers, and washing machines can be considered. Each of these has its flow rate, which you need to add up to get the total number required. Tubs and showers are the biggest spenders in the category and vary from 2.5 to 4 gallons per minute. An average faucet might not need more than 0.75 GPM. If you plan to run these simultaneously, the total flow rate must cover the requirements of both units.

  • Temperature rise

    The things to consider now are the current water temperature and the preferred output level. There are methods to measure current water heater, but you can also assume it is 50F. As it is a fairly low assumption, you will be on the safe side that the rise will be adequate. Now, most people aim for their water to be around 100-115 degrees. That means you should aim for a temperature rise of about 55 degrees.

Choosing the right size of a gas tankless water heater gets trickier the more space you need to heat. Although these are the general rules, consider asking a professional for an opinion before purchasing a particular unit.

Indoor VS. Outdoor Gas Tankless Water Heaters

Indoor-VS.-Outdoor-Gas-Tankless-Water-HeatersThere are two alternatives for the location of the unit when buying a gas tankless water heater. The first option is to place the unit indoors, and the other is to take it outdoors. The majority of tankless heaters, however, are manufactured to be placed inside of a property. Some of them may be versatile and also have both options available. Even though they are indoor models by default, they come with a conversion kit for those who want to install them outside.

Aside from the obvious installation location, the main difference between indoor and outdoor gas tankless water heaters is the necessity for venting. The outdoor units do not require a venting system since they are placed outside. Therefore making them suitable for those properties where it is hard to install vent pipes inside. Additionally, they are also adequate for people looking for an entirely risk-free option. If you are installing a gas-powered model, it is better to place it outside the house, right?

Which Are Safer – Indoor or Outdoor Units?

The truth is that both types are equally safe. As long as you ensure proper installation and maintenance, the safety shouldn’t be a problem. The crucial thing to consider is that you need to find a venting solution when placing a gas heater indoors. Venting must involve an exhaust pipe that will eliminate all dangerous gasses emitted when the unit is working. The exhaust pipes should be as straight as possible (minimum number of elbows).

Additionally, when installing an indoor unit, you must consider fresh air intake. Some locations will have fresh air by default while others will require an intake vent. Its task will be to get the air from the outside and also secure optimal conditions for the gas heater to work.

Propane VS. Natural Gas Tankless Water Heaters

Propane VS. Natural Gas Tankless Water HeatersIf you set your mind on buying a gas water heater, you will have two options at your disposal – propane and natural gas. Both options have their advantages, as well as drawbacks, and we will discuss them in this section.

Advantages of Propane Tankless Water Heaters

The biggest advantage of propane is its availability and accessibility. During the installation process, a propane storage canister (or tank) in a convenient spot on your property and that will be the fuel source for your heater. It is interesting to mention that propane comes in its liquid state. This type of gas is available in all areas, and also, its installation process is quite simple.

Here are the pros of propane tankless water heaters:

  • It is more efficient in heating the water
  • Might be the only option available in some areas
  • A more convenient installation process

Advantages of Natural Gas Tankless Water Heaters

natural-gas-tankless-water-heaterAs for the natural gas, installing a tankless water heater will be effortless if your home already has a gas line. However, if one is not present, you will need to bring it to your home. In most cases, you can check out if there is a natural gas line near your street and pay to expand the pipeline to your property.

The crucial advantage of natural gas is that its supply is constant and endless. There is no need to monitor the level of remaining gas like with a propane tank. Naturally, you have the option of agreeing with your propane provider to automatically fill the storage container so that you wouldn’t worry about the remaining fuel level.

Let’s take a look at the pros of natural gas tankless water heaters:

  • The cost of usage is lower than propane
  • No worrying about remaining gas storage
  • Low explosive risk

Other Things to Consider

If you are wondering about the cost, many people would initially think that natural gas is cheaper and they would be right. Its default cost is significantly less when compared to propane, but you should also consider the cost-efficiency ratio. Propane is more efficient in heating your home as it has 2490 BTUs while natural gas has 1030 BTUs. This is an abbreviation for a British Thermal Unit, and it is an internationally accepted unit of heat efficiency.

Natural gas tankless heaters can still do an excellent job is heating water while keeping a fairly low cost on a per-unit basis. If the price is your primary consideration, aside from utility bills, you should also consider the cost of installation and the overall specifics of your home. Are there any other appliances powered by gas in your house? Is natural gas available close to your house and can it easily be delivered to your property? Try to estimate installation and usage costs of both variants, as well as the cost-efficiency ratio. That is how you can make the right decision regarding the best option for your needs.

The important thing to keep in mind is that both propane and natural gas are safe options. We recommend having them installed by a professional, but as long as everything is set up and maintained properly, there will be no reason to worry while using them. That being said, propane is a higher explosive risk than natural gas in theory. Natural gas is lighter and may rise in the air and dissipate. For more information check out The guide to propane vs. natural gas

Features of Commercial Tankless Gas Water Heaters

When discussing commercial gas tankless water heaters, their primary task is to heat water in large properties. These may be office buildings, apartment complexes, or even hotels. When choosing a commercial heater, the crucial thing to consider is whether it can meet the hot water need of everyone on the property.

You should take into account that there are periods when plenty of users may require hot water at the same time. These situations most often occur in the morning and late in the evening. It is why you need to buy a unit that will do a solid job in providing hot water to everyone regardless of the demand.

How Do I Choose a Commercial Tankless Gas Water Heater?

The crucial feature that distinguishes commercial heaters is the size and power of the unit. In this situation, size matters and it is something to take into account. If you are heating an office building, you will need a unit of sufficient size to handle that job. The first thing to consider is the flow rate as that is how you will accommodate simultaneous multiple requests for hot water.

Another thing to consider is how many BTUs a heater can deliver. It does not mean much to have a unit with a large storage tank that is not efficient enough in heating the water. The BTUs will become especially important in peak hours. Commercial heaters can vary in heat input from 50,000 BTUs to 1 million BTUs. Try to find the right balance and identify the power your property needs. That way you will optimize utility costs and efficiency.

Residential Vs. Commercial Tankless Gas Water Heaters

While browsing offered heaters online, you have surely encountered residential and commercial options, as well as some versatile ones who can serve for both types of properties. The truth is that both unit types work in a similar way with the crucial differences being sizing and gas input.

Residential tankless gas water heaters have a purpose of securing hot water in a home while commercial units have the same task in larger properties, such as hotels or apartment complexes. That is why commercial heaters need to be large themselves. In most cases, you will find that units for commercial properties have a considerable larger flow rate.

For a single faucet, even 1.5 GPM may be enough. However, for multiple simultaneous usages and several household members, you will need anywhere from 4 to 10 GPM. Residential heaters rarely exceed this limit, but if you have a huge home, you can even consider buying a commercial unit to ensure that it meets the needs of all residents.

The Importance of BTUs

When it comes to gas input, the general rule of thumb is that a residential tankless gas water heater can deliver up to 75,000 BTUs. On the other hand, commercial setups can go up to 1,000,000 BTU, which is quite impressive. The key thing to consider is the number of BTUs sufficient for your property. You do not want to risk that a resident (or hotel guest) doesn’t have hot water whenever they need it. However, you also don’t want to spend more than it is necessary for installation and usage.

Ultimately, residential and commercial options are only different in the size they take and the amount of water they can heat. It is not uncommon for them to overlap, especially when commercial units are used in large private homes. It might be wise to ask a professional for an opinion before deciding on the right option for your property.

Tankless Gas Water Heater Installation & Venting

tankless-gas-water-heater-installation-Once you choose your desired unit, you still need to take care of proper installation. Setting everything up properly is essential as it ensures both safety and maximum efficiency of the unit. Here is an overview of the steps to consider during the installation process:

  • Picking the location

    Before purchasing a unit, consider whether it will serve as an indoor or outdoor heater. A professional will start by inspecting your property and trying to find an optimal area for placing the unit. The choice will depend on the property size and other characteristics, as well as where you primary need hot water. The venting options will also be a primary consideration to ensure optimal safety. If possible, go with the same location of your previous heater as that simplifies the installation/

  • Installing it on the wall

    It will be one of the possible options. If you go with it, make sure to follow the instruction manual to the detail and use all the required pieces.

  • Connecting to the gas line

    Ensure that the gas pressure in line with what the rating plate specifies. Pipes that you utilize shouldn’t be smaller than the diameter of the heater connections. Use the soap-water solution to check for potential gas leaks.

If you do not have any previous experience, we would suggest hiring a professional to handle the installation.
outdoor-tankless-gas-water-heaterNow, why venting is a primary consideration when installing a water heater? The reason is optimal indoor air quality and safety of those inside the property. If you are installing the heater outdoor, you do not need to worry about venting. However, indoor heaters produce carbon monoxide and other hazardous gases.

The general things to keep in mind is that exhaust gases should be vented and fresh air intake should be secured. When choosing a vent option, you can go with power and direct venting. The power option involves placing an exhaust vent for getting rid of dangerous gasses. Keep in mind that the length and the elbow number should be at a minimum for optimal venting.

When it comes to direct unit, you will install both exhaust and intake vents. You should go with this option when there is not enough fresh air secured naturally. An intake vent will pull the air from the outside through the vent.

Flushing a Gas Tankless Water Heater

It is important for your system to have isolation valves with service ports because you need it to flush a tankless water heater. Some tankless water heater makers add these fixtures to their systems, but in most cases, your plumber will be the one to provide them during the installation of the system.

Required Supplies

  • Adjustable wrench
  • Screwdriver
  • Needle nose pliers
  • Two 6-ft washing machine hoses
  • Submersible pump
  • 4-gallons of virgin, food grade white vinegar
  • Non-contact voltage tester

Step by Step Guide

  • Step 1

    The first step is to disconnect the electrical power to the gas tankless water heater. Next, remove the cover of the compartment and use your non-contact voltage tester to check for the presence of electrical current in the system. The Hot and Cold Shut-off Valves should be closed to prevent cold water from getting into your unit and household plumbing system.
    Open the hot water pressure relief valve, which can be found on the hot water line to reduce the pressure. Take care to avoid scalding by the hot water that might come out of the valves. To the Cold Water Service Port, connect one end of the first hose while the other end of the hose should be connected to a submersible pump.

    Transfer the submersible pump into a five-gallon bucket. To the Hot Water Service Port, connect one end of the second hose and place the free end of the hose into the bucket. Pour the four gallons of undiluted vinegar into the 5-gallon bucket into which you placed the submersible pump.

  • Step 2

    In step two, the Hot and Cold Service Ports will be opened to pump the vinegar into the unit to dilute and wash off mineral sediments.

    Power the submersible pump and let the vinegar circulate through the tankless water heater for a minimum of 60 minutes if the pump operates at a rate of 4-gallon per minute, and longer if it is slower. The vinegar will help to break down and flush out the accumulated limescale in the unit.

    Now, switch off the submersible pump and get rid of the vinegar. Once you are through with the flushing, it is time to rinse the vinegar out of the unit.

    To rinse out the vinegar, take the unattached end of the second hose out of the bucket and transfer it into a receptacle or drain. Then remove the first hose, close the Cold Water Service Port, and open the Cold Water Shut-off Valve. Meanwhile, keep the Hot Water Shut-off Valve closed.

    After opening the Cold Water Service Valve, fresh water will start flushing out remnants of the vinegar via the second hose. Leave the water to run for ten minutes, before closing the Cold Water Shut-off Valve to stop water from passing through the unit. After stopping the water, remove the second hose and shut the Hot Water Service Port.

  • Step 3

    The first step is to remove the Cold Water Inlet Filter. If your unit also comes with a Hot Water Inlet Filter, you need to clean it as well. Next, use tap water to flush and rinse sediments out of the Cold Water Inlet Filter screen and compartment.

    After flushing the compartment, the Cold Water Inlet Filter should be covered and secured tightly before opening the Cold Water Shut-off Valve. Then return the cover of the access panel and switch on the power to the heater unit.


Who Installs Tankless Gas Water Heaters?

Each tankless gas water heater comes with an instruction manual to follow. Despite that, there are many reasons why you should trust a professional to install the unit. These include:

  • Picking the right location – ensure optimal performance of the heater.
  • User safety – make sure the installation went smoothly, and you can safely use the unit.
  • Saves time and effort – why would you waste hours or days on installing the heater? Instead, call a professional and relax while they handle the setting up process.

Can I Use Gas Tankless Water Heaters in High Altitude Areas?

Yes, you can use them in areas with high altitude, but you need to keep in mind that height affects their performance. Everything should function flawlessly until you reach 4,000 ft of altitude. From that point, a gas heater loses in its efficiency. The estimation is that the BTU decreases for about 4% with every additional 1,000 feet of altitude. Therefore, it means you may need stronger units to meet the required needs at high altitudes.

Can Gas Tankless Water Heaters Save a Lot of Money?

When it comes to utility costs, yes, they can be significantly cheaper than other heating options. However, keep in mind that you also need to cover installation charges. That means it may take a while before your tankless unit turns out to be a smart investment. In the long run, it is one of the most affordable options out there. Add to that the fact that it secures endless hot water supply and you’ve got yourself a reliable heating option that doesn’t cost a lot of money to run.

Check with our homepage to see if you’ve missed anything important!

Wrap Up

That rounds up the tankless gas water heater reviews! We hope that you enjoyed reading the article, including our buying guide that covered everything that you should know about these types of heating units.
Now that you know what to look for, have you found the best tankless gas water heater yet?

If you have a natural gas line in your house, that might be the simplest choice, but you can always go with propane if that is your preferred option. Do you plan to use it for your home or on the go? Would you like to install it indoor or outdoor? Either way, check out the reviews again and you might find a model that suits your needs.

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