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The Best Outdoor Tankless Water Heaters

Fact checked by Stephen Conklin

best outdoor tankless water heater

The best outdoor tankless water heater is not only ideal for modern, energy savings-conscious households. It is also the perfect solution for people living off the grid and those having a wonderful time in the great outdoors. You will never run out of hot water or worry about high energy bills as long as you pick the best outdoor tankless water heating appliance.


Top 1

Rinnai RL94eN

Capacity 35.5 Liters
Voltage 120 V
Flow Rate 9.8 GPM

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Top 2

Eccotemp ‎L5

Capacity 5 Liters
Voltage 3 V
Flow Rate 1.5 GPM

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Top 3

Camplux BW422LP

Capacity 16 Liters
Voltage 3 V
Flow Rate 4.22 GPM

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Table of Contents

Best Outdoor Tankless Water Heater Reviews

1. Rinnai RL 94eN Outdoor Tankless Hot Water Heater

People trust a Rinnai tankless water heater to provide them with the best value for every penny they spend. Its advanced features and reliable performance are often enough to disregard the product’s minor flaws. That is what you get with the Rinnai RL 94eN.

Running on natural gas, this outdoor tankless water heater has the highest flow rate on this list. Depending on the groundwater temperature, you can enjoy up to 9.4 gallons per minute. It is enough to supply hot water to four people showering simultaneously.

There are no worries about its heating efficiency, either. You can enjoy up to 40% higher natural gas savings than using tanked water heaters. It has an EF rating of 0.82, making it on par with other high-end units. That is additional savings to go into your vacation fund.

I love its Circ-Logic technology because it memorizes your hot water consumption habits and patterns. It automatically puts its heavy-duty heat exchanger and heating element on standby, ready to kick in when you turn on your faucet or showerhead.

I also like its WiFi compatibility. While that translates to additional expense, I still recommend getting the wireless module if you want absolute convenience. Rinnai products are very durable, often lasting two decades or more. This product has one of the longest warranties I have seen so far for a natural gas tankless system.

Unfortunately, this outdoor tankless water heater is not Energy Star qualified.
  • High-efficiency design for cost and fuel savings
  • Ultra-high flow for consumption
  • Advanced Circ-Logic technology for more efficient operation
  • WiFi capable for easier control
  • Very durable construction
  • Longer warranty than other brands
  • Not Energy Star qualified
Regardless, this flaw is minor compared to what the Rinnai RL 94eN can provide your family. It is one of the best natural gas outdoor tankless water heaters you can ever buy because of its efficiency, convenience, performance, and durability. Frankly, I cannot ask more.

2. EccoTemp L5 Portable Outdoor Tankless Water Heater

The best outdoor propane tankless water heater lets you enjoy hot showers wherever you go outside your house. You can wake up to a more beautiful morning in the campgrounds, not worrying about a cold shower. Bathing your dogs or horses or giving the kids a warm pool party is also possible. As long as you have the EccoTemp L5, a hot shower is always available.

I like the device’s straightforward user controls. The unit features two separate dials for controlling fuel expenditure and water temperature. A 20-pound propane tank is enough to give you hot water for several weeks outside your home. It can raise the temperature to 140 degrees Fahrenheit, although 110 degrees is comfortable enough for most folks.

The water heater’s control mechanism allows it to produce hot water even with a low water pressure of 20 PSI. Never again will you complain about cold showers. Your horse or dog will also feel more relaxed during bath time.

You can also rest easy about this appliance’s quality and performance. It has CSA certification to make you feel more confident whenever you use it.

Because it is portable, it can only deliver a maximum flow speed of 1.5 GPM. It is still better than other tankless water heaters I know. If this bothers you, you can buy the 12V EccoFlo water pump to increase the heater’s flow rate to 3 GPM.

I wish the company provided an AC or a 12V DC port so that you can plug it into your car’s electrical system or an electrical outlet. It would be best to buy two D-cell batteries for this unit.
  • Ideal for outdoor recreational activities
  • Two separate control dials for fuel and water
  • Affordable; portable design for versatility
  • 140-degree Fahrenheit maximum temperature
  • Works with low water pressure
  • CSA certification for greater confidence in the product
  • Modest flow speed
  • Two D-cell batteries required
The EccoTemp L5 makes for an interesting propane-powered tankless water heater. This top pick is portable and versatile, allowing you to use it in numerous applications. It is affordable, too.

3. Camplux BW422LP 16L Outdoor Propane Tankless Water Heater

People living off the grid require a reliable and efficient system for heating water. One of the most exciting products they can ever get for outdoor applications is the Camplux BW422LP. This high efficiency outdoor tankless water heater has enough bells and whistles to make it your go-to water heater whenever you are outside your home.

I appreciate the device’s unique heating mechanism, featuring a stainless steel burner and a tinning copper heat exchanger. These components give the product a remarkable 88.5% thermal efficiency, minimizing heat loss while ensuring substantial savings.

The burner can produce a maximum of 110,000 BTU per hour, ensuring you get hot liquids fast. Its 4.22-GPM flow is also higher than other tankless water heaters I know. Homeowners and off-the-grid enthusiasts will love this appliance’s water heating capabilities.

There is also no need to fret about the elements wreaking havoc on this device. It has freeze protection to keep it running even in sub-zero temperatures. The appliance also has safety features against excessively high water pressure, low water flow, and overheating. The flame failure device works like a charm, too.

Using this appliance outdoors is worth it. You can bring it to the campgrounds, bathe your dogs and horses, and give your kids a warm shower after a day in the swimming pool.

With these innovations, this appliance is about 30% more expensive than other brands. While I appreciate using D-cell batteries for ignition, I wish the company already included a pair.
  • 5% thermal efficiency for greater cost savings
  • 22 GPM maximum flow for use
  • 110,000 BTU per hour output for faster heating
  • Multiple device protection features for safety
  • High-quality CSA-certified components
  • More expensive than other brands
  • No batteries included
Nevertheless, the product’s CSA certification is another reason you should get the Camplux BW422LP. Not only does it have an exemplary water heating performance, this top pick is also portable enough to make it an all-around water heater whenever you head outdoors.

4. GASLAND BS318 Outdoor Propane Tankless Water Heater

An outdoor tankless gas water heater gives you hot water wherever you are. You may be camping with your family, enjoying a summer picnic, or letting your kids have fun in the backyard. A compact tankless water heater will give you the joys you want.

An excellent product to get is the GASLAND BS318, a reliable tankless water heater that runs on ordinary propane. It is the perfect portable water heating solution for your camper, cabin, RV, work shed, garage, or backyard.

I like this appliance’s GPM rating because it is higher than other products. At 3.18 GPM, you can enjoy hot showers for a longer time. The savings are substantial, too. The system can provide you with up to 11.5% in energy reserves.

I know you will also love this water heater’s 82,000 BTU/hour heating element. You can quickly raise the temperature to your preferred level, reducing wait times.

One thing about outdoor devices is that they are at the mercy of the elements. Thankfully, this product has an anti-freezing technology that safeguards its integrity when environmental temperature drops. There is a built-in flame failure mechanism, too, ensuring safety when there is no oxygen in the burner.

Unfortunately, the company does not recommend using this water heater in areas located about 3,300 feet above sea level. Using it in windy conditions can also reduce fuel efficiency. Given that it has limitations, I find its price tag somewhat more prohibitive than other products with similar specifications.
  • Higher-than-average flow for use
  • 5% energy-saving technology for enhanced cost savings
  • 82,000 BTU/hour thermal output for faster heating
  • Multiple device safety features for enhanced security
  • Compact and suitable for multiple applications
  • Not recommended for windy conditions and high-altitude areas
  • A bit expensive
Nevertheless, the GASLAND BS318 remains a top pick for RVers, campers, and people living off the grid. It is quick to heat the water and provide you with sufficient hot water for different applications simultaneously.

5. Camplux Pro BD264N Tankless Outdoor Propane Water Heater

If you are beginning to enjoy the freedom of living off the grid, the Camplux Pro BD264N is always an excellent appliance to purchase. You do not have to worry about powering it because it only relies on a pair of lithium batteries.

This outdoor tankless propane water heater has a 68,000 BTU/hour heating element, sufficient to provide a family of three with hot water for their needs.

The water heating appliance has several features that improve its safety. There is an overheat protection and anti-freezing mechanism to keep your unit running even in the dead of winter. It also comes with a flame failure device, making you feel safe when you sleep at night.

I love the water heater’s heating element and heat exchanger design, featuring tinning copper and stainless steel. Not only do these materials guarantee exceptional durability, they also contribute to the water heater’s 11.5% fuel-saving design.

There is no hocus-pocus on the brand’s claims because it has the backing of a valid CSA certification. At least, you will feel more confident about this product’s quality. Living off the grid should be as convenient and comfortable as living in a posh subdivision.

Unfortunately, its 2.64 GPM flow may be insufficient for some folks. That is why I only recommend this appliance for two to three persons. Additionally, its modest flow rate makes its price tag a bit unjustified.
  • Easy to power with lithium batteries
  • Ideal for off-grid living and outdoor activities
  • Heavy-duty, high-performance water heating elements for fuel savings
  • 68000 BTU/hour output for efficient heating
  • Multiple device safety features for adequate security
  • Premium CSA-certified parts
  • A little bit expensive
  • Modest water flow
Many homeowners consider the Camplux Pro BD264N their top pick, making it an excellent choice for their off-the-grid living or outdoor adventures. Whether it is for camping, vacationing, RVing, or any other outdoor activity, this product delivers hot water whenever you need it.

6. EZ CampChamp Propane Outdoor Tankless Water Heater

EZ CampChamp may not have a large fan base, but it is slowly making a name for itself. This outdoor propane tankless water heater affords anyone the luxury of hot showers and hot liquid, wherever they may be.

True to its promise, this compact water heating appliance can deliver warm water continuously without experiencing a substantial temperature drop. One can never question its energy efficiency because you will only use propane to power up its burner.

I like the simplified layout, making for effortless control. A simple twist of the dial is enough to set the appliance in its water heating capabilities. Families will love its hassle-free operation. Even kids will not have issues operating this device.

The carrying handle is large and heavy-duty, allowing you to hang the tankless unit on any stable and sturdy structure. It is the perfect solution for getting an instant hot shower in your backyard or a warm water bath for your dogs.

Unlike other products that require additional purchases of mounting or installation materials, this product already comes complete. The fuel line and port are heavy-duty and can connect securely to standard propane tanks. I also appreciate the inclusion of a showerhead, perfect for having a hot spray on a cold and windy afternoon.

My only lament is the product’s limited 1-year warranty. An average tankless unit has at least five years of guarantee. The flow rate can also leave you wanting more. At only 1.8 GPM, this is a water heater you cannot expect to deliver warm water to two people showering simultaneously.
  • Energy-efficient water heater for outdoor applications
  • Compact design with a carrying handle
  • Simple controls for hassle-free operation
  • Complete kit with a showerhead
  • Not hard to set up
  • Only 1-year warranty
  • Modest flow rate
Regardless, the EZ CampChamp gas water heater is still an excellent choice for those who require only modest amounts of hot water whenever they are outdoors. It is effortless to set up and hassle-free to operate.

7. Noritz NR50ODNG Outdoor Tankless Water Heater

The Noritz NR50ODNG is a reliable and efficient tankless water heater for a modern home. It uses natural gas to fuel its burner, raising the temperature to comfortable levels fast. Insufficient hot water supply will never be an issue again.

Inside this device is a heavy-duty natural gas burner that produces 120,000 BTUs per hour, cutting heating time by several minutes. Because it heats fast, you will never worry about spending too much fuel. You will notice an improvement in your natural gas bills, putting savings in your vacation fund.

The product’s Energy Star qualification can also put your mind at ease. Your family will love taking hot showers, giving your pets a warm bath, and washing the clothes more efficiently.

The average tankless water heater has a flow rate of about 2 to 2.5 gallons per minute. This water heater doubles the industry average, giving you up to 5 GPM for your needs. Showering will be more fun, and washing the dishes will be more efficient with a steady hot water supply in your home.

I also like its simple design, ensuring hassle-free installation. That is additional savings for you and your family. My only concern is that the company does not provide an installation kit with this tankless heater. You will have to purchase the kit separately. You may shell out more money than you expected, making it more expensive than an outdoor tankless water heater electric product.
  • 120,000 BTU/hour output for super-fast heating
  • Higher-than-average flow for water use
  • High-efficiency heating components for greater savings
  • Energy Star qualification for peace of mind
  • Effortless to install
  • No installation kit included
  • Very expensive, when factoring in the installation kit
All is good, nevertheless. After all, very few tankless water heaters for the outdoors are as efficient and powerful as the Noritz NR50ODNG. It is straightforward to install and delivers hot water to two people showering simultaneously.

8. Camplux Pro WA686LP On-Demand Tankless Water Heater

Camplux is a brand that many modern homeowners trust, providing them with exceptionally high performance and advanced water heaters. Take the company’s Pro WA686LP tankless water heater for instance. Not only does this appliance have a dashing look, it also outperforms other brands.

Among the tankless water heaters I reviewed, the WA686LP has the highest BTU/hour rating of 180,000. This appliance can raise the temperature within a couple of minutes, letting you enjoy a hot shower in no time.

Since the water heater has a 6.86 GPM maximum flow, you and two other household members can enjoy a hot shower simultaneously. You will never experience a substantial drop in temperature. Plus, its 0.82 EF rating is still higher than conventional tanked water heaters.

Like many Camplux products, I love this appliance’s multiple device features. You do not need to build an outdoor tankless water heater enclosure to protect it against freezing because it already has advanced freeze protection. The device also has a protective system in case of flame failure.

I love the addition of a remote controller for the device, complete with a bright LED screen and responsive control buttons. I only wish the company designed the controller wirelessly. Its 3.3-foot cable may not be long enough for some people.

I am not sure if the advanced technologies integrated into this outdoor tankless water heater are enough justification for its hefty price tag. I have seen products that offer a higher flow rate and better fuel efficiency rating, too.
  • 180,000 BTU thermal output for super-fast heating
  • For those who want conventional tankless water heaters with fast flows
  • Multiple safety features for device security
  • User-friendly remote controller for convenience
  • 82 energy rating for efficiency
  • Not budget-friendly
  • Not wireless remote controller
Nevertheless, the Camplux Pro WA686LP remains a fantastic choice for small to medium-sized families. Its efficiency is spot-on, and its operational convenience is something that many modern homes will find appealing.

9. VIVOHOME Outdoor Portable Propane Tankless Water Heater

Enjoying outdoor activities does not mean you have to make do with cold showers. If you get the VIVOHOME portable tankless water heater, you can guarantee hot water for everyone in your family wherever your adventure takes you.

As a portable outside tankless water heater, this appliance comes with enough features to deliver hot water on the go. It is perfect for off-grid living, camping, fishing, and other outdoor activities. You can even bathe your pets in your backyard or give your kids a warm shower after coming out of the swimming pool.

This appliance does not require a lot of fuel to heat water because it already has automatic features. It ignites the burner the moment you turn on your showerhead or faucet. It also automatically switches off the burner once you close the hot water fixtures.

I love the water heater’s winter and summer modes, ensuring optimum functionality in all conditions. It also helps that the product already comes with anti-freezing technology and three other protective mechanisms. These features are essential in ensuring the water heater’s optimum function, regardless of weather conditions.

Like many portable units, this product can only provide a measly 1.6 gallons of hot water per minute. It may be insufficient for some families that love to shower simultaneously. The digital display is also small, making some people strain to read the temperature.
  • Summer and winter modes for effortless operation
  • Multiple protective mechanisms for safety
  • Portable design for off-grid living and outdoor activities
  • Automatic features for low energy consumption and better savings
  • Modest flow per minute
  • Small digital display
The VIVOHOME Outdoor Portable Propane Gas Tankless Water Heater remains an excellent choice for adventurous families. They can bring the unit to their weekend trips and never worry about not having plenty of hot water again.

10. Thermomate ZERO16 Propane Tankless Water Heater

If you are looking for an efficient water heater for your camper, RV, boat, or cabin, the Thermomate ZERO16 is a wise choice. This small and compact tankless water heater works like a charm, providing you with hot water wherever you are.

What makes this water heater fascinating is its dual solenoid valve design. The feature allows the water heater to begin heating even with low water pressure. Whereas other devices only start heating the water if it senses a minimum of 3 PSI, this product kick starts the water heating process with only 0.7 PSI of water pressure.

Unlike other portable water heaters, this appliance also has a higher water flow of 4.23 GPM. Your family members will never complain about cold water or insufficient hot water for their activities.

Like many outdoor units, the ZERO16 also has anti-freeze technology and a flame failure device. It can make your outdoor adventures more worthwhile because there are no worries about putting your family in harm’s way.

I love its sleek and uncluttered design. The controls are pretty straightforward, although I wish the company made a larger digital temperature display. Given that its only real advantage over other brands is its dual solenoid design, I find its price on the high side.
  • Works in many settings
  • Dual solenoid valves for a lower water pressure activation than other brands
  • Faster flow than other outdoor tankless water heaters
  • Multiple protective mechanisms for improved safety
  • Uncluttered and sleek design
  • Small temperature display
  • Expensive for its features
Nevertheless, the Thermomate ZERO16 deserves your consideration, especially if you love going outdoors with your family. Having hot showers wherever you park your RV or camper is a guarantee many outgoing families will never want to miss.

11. Botabay Tankless Water Heater

Most outdoor propane water heaters on this list can cost you more than a couple of hundred dollars. The Botabay Tankless Water Heater does not, making it the ideal water heating solution for budget-conscious families without sacrificing performance and efficiency.

As an outdoor unit, this appliance has enough protection to keep it running regardless of weather conditions. There is no need to protect it against freezing because it already has a built-in mechanism. The water heater also guards against overheating and flameouts. It automatically shuts off if the temperature exceeds 167 degrees Fahrenheit. The 20-minute timer also helps.

Families will love its 4.3 GPM flow speed, ensuring an adequate hot liquid supply for a household of three. I love the separate winter and summer modes, saving you up to 40% energy. Growing your vacation fund is effortless with this device.

I like this appliance’s T13 burner because of its durability and high-performance heating. It contributes to the water heater’s remarkable fuel efficiency that translates to better savings for your family.

While it is affordable, this appliance is not very easy to install. The manufacturer recommends consulting a professional for the setup.
  • 3 GPM flow for better water consumption
  • High-efficiency burner for better energy efficiency
  • Various protective mechanisms for increased safety
  • Winter and summer modes for improved fuel efficiency
  • More affordable than other portable outdoor tankless water heaters
  • Difficult to install
Despite this drawback, I believe the Botabay Tankless Water Heater deserves your consideration. It is an affordable outdoor water heater that delivers a steady and sufficient hot water supply to your home. Safe and effortless to operate, this appliance should fit right into a modern house’s domestic heating system.

12. Noritz NR662-ODNG Outdoor Tankless Water Heater

Noritz returns to our list with its NR662-ODNG, offering homeowners reliability, performance, and durability in a compact package. As simple as it may look, this outdoor tankless water heater can effectively replace your old and lumbering appliance. It can give you the savings you need for your family to enjoy.

Heating the water is efficient with this appliance’s 140,000 BTU/hour burner. While it may take several seconds longer than other brands to heat the water, it never fails to maintain its set temperature once it gets going.

If you also factor in the water heater’s 6.6 GPM flow speed, you know you have a clear winner in your hands. Not only does it guarantee endless hot fluids for a three-member family, it also has a thermal efficiency of 84%. Its 0.81 UEF rating may seem not much, but it is still better than the industry average.

I like its simple design that doesn’t undermine its quality construction. I can only assume that its thermal efficiency has something to do with its energy-efficient burner and heat exchanger elements. The thoughtful design also reduces nitrogen oxide emissions, making it safe to have around outside the house.

While this outdoor water heater seems pretty straightforward to install, I still recommend getting a professional to install it. Doing so tends to jack up its initial cost, especially since this product does not come with an installation kit. Getting a professional will help you determine the best hardware to use for its mounting.
  • 140,000 BTU/hour power output for efficient heating
  • 6 GPM flow for convenience
  • Nice UEF rating and thermal efficiency
  • Solid construction for durability
  • Low NOx emissions
  • Expert installation recommended
  • Installation kit sold separately
Other than these concerns, the Noritz NR662-ODNG remains an exciting option for many families. It is reliably efficient and provides your family with an uninterrupted hot fluid supply without jacking up your energy costs.

13. FORUEE PERFRCT F10 Tankless Water Heater

This brand may not ring a bell, but the FORUEE PERFECT F10 is one of the best-selling outdoor propane tankless water heaters on the market today. I think it deserves the top pick on this list. You only need to look at its average rating on outdoor propane tankless water heater reviews, and you will know why this is a wise investment.

I like its fast-heating element, producing 68,000 BTU per hour to increase the water temperature by an additional 102 degrees Fahrenheit at 1.5 gallons per minute. If your groundwater temperature is 60 degrees, you can enjoy a maximum flow of 2.64 GPM at a super-hot 132 degrees Fahrenheit.

I also love the appliance’s safety features, especially the oxygen depletion automatic shut-off system. Never will you worry about overheating, accidental flameouts, and freezing. You will also like its strong wind protection and thermal protection features.

You might think these features are a marketing gimmick. They are not. The product has a UL and CSA certification for its critical components. A sound sleep is in the offing, knowing you have a reliable and safe product.

This water heater is perfect for any outdoor application, including camping, RVing, hunting, pet care, and many more.

I cannot find any substantial flaw in this water heater, except its higher price tag than other products with the same design. While its flow rate is well within industry standards, some folks may still find it insufficient.
  • 72-degree Fahrenheit temperature rise at 2.64 GPM
  • 68,000 BTU/hour for faster heating
  • Versatile design for multiple applications
  • Six device security technologies for safety
  • UL and CSA certification for peace of mind
  • A bit costly
  • Not recommended for high volume use
Regardless, I can say that the FORUEE PERFECT F10 deserves respect alongside other top pick brands like Rheem and Rinnai. The device has excellent protection against the elements, is exceptionally portable and versatile, and has the approval of two of the world’s most trusted quality organizations.

What is the Best Outdoor Tankless Water Heater/ Who This is for


Outdoor tankless water heaters have all the efficient and high-performance features of any other domestic liquid heating system. However, what sets an outdoor tankless unit apart from other types is weatherproofing.

Since an outdoor unit is at the mercy of the elements, it should have adequate protective mechanisms to guarantee its optimal functioning. It can withstand adverse weather conditions, including strong winds, freezing temperatures, severe storms, and other forces of nature.

The best outdoor tankless unit is suitable for anyone who wants an efficient fluid heating system in their home, backyard, or anywhere they decide to go. It is perfect for off-grid enthusiasts, campers, anglers, road trippers, hobbyists, and more. A tankless heater unit is always a wise choice whenever there is a need for a hot liquid supply.

How Do Outdoor Tankless Water Heaters Work

Tankless water heaters work like any other liquid heating device. Inside the unit are tubes that run through a burner or heating element and a heat exchanger.

An intake port receives cold liquid that passes through the heating element. As the fluid moves through the internal pipes, heat transfers to the liquid and increases its temperature. The fluid moves out of the heater unit and to your plumbing line.

There are two heating options for tankless water heaters. One uses natural gas or propane, while the other uses electricity. An electric tankless water heater connects to your electric supply that powers the heating element. On the other hand, gas tanks supply fuel to the burner.

Outdoor Tankless Water Heater Buying Guide

Choosing the best outdoor tankless water heaters is not complicated. One only needs to ask a few questions to determine the correct tankless unit for the house.

Portable or Fixed?

It would be best to ask yourself whether to buy a portable unit or one that you can fix permanently outside your house.

Most outdoor tankless water heaters are portable devices. One can bring a unit to the campgrounds and never worry about a cold shower ever again. A handy product is suitable for people who love to travel with their families. This unit is also ideal for backyard activities, such as bathing pets, cleaning the garage, and more. The downside to these tankless water heaters is their low GPM rating.

On the other hand, a fixed unit is suitable for homes that want their heating device outside the house for safety concerns. These water heaters often run on natural gas. These types also provide higher GPM ratings for optimum consumption.

Electric or Gas?

Should you pick an electric tankless water heater? Or is a propane or NG product more appealing? In general, a propane-powered unit is more cost-effective in the long run because of its lower fuel unit price compared to electricity. However, a fuel-powered product is often more expensive at the onset.

Correct Size

In determining the correct size of tankless water heater to buy, you should assess two things. First, consider how many gallons flow through each of your fixtures and appliances per minute. For example, a kitchen faucet may have a GPM of 1, while a showerhead can have 2.5 GPM.

If you have three faucets and one bathroom, it is safe to assume that about 5.5 GPM is needed when your fixtures are opened simultaneously. As such, the right size of the tankless water heater product is 5.5 GPM.

Second, consider the groundwater temperature and your ideal temperature. Determine the difference between the two to know the temperature rise you need from your outdoor tankless heater. If your intake temperature is 50 degrees Fahrenheit and you want a 110-degree shower, the temperature rise you seek is 60 degrees Fahrenheit.

Hence, you should pick an outdoor tankless heater with 5.5 GPM at a 60-degree rise.

Installation Ease

Some manufacturers require expert installation for their products, lest you void their warranty. You may want to read tankless water heater reviews to understand whether installing the product yourself is worthwhile or not.

In general, installing tankless electric water heaters is more straightforward than installing gas models.


Reading outdoor tankless water heater reviews can give you an idea about the real-life warranty of a product you wish to buy. It is worth noting that some companies offer 10 to 20 years’ warranty, while others may only provide 1 to 2 years. Some brands may even fail to honor their warranty.

Frequently Asked Questions 


Who makes the best outdoor tankless water heater?

Rinnai and Rheem are two brands that make the top-rated outdoor tankless water heaters. They have excellent weather protection, including advanced freeze protection technology.

Among the heaters we reviewed, FORUEE makes the best propane outdoor tankless water heater. It has the same advanced freeze protection as Rinnai and Rheem heaters and a few other technological features that outperform other brands.

Other notable brands include Camplux, EccoTemp, Noritz, GASLAND, EZ Tankless, Thermomate, VIVOHOME, and Botabay.

What size outdoor tankless water heater do I need?

Two factors play a role in determining the correct size of an outdoor tankless water heater: temperature rise and flow rate. To do this, you need to do a little math.

  • Determine how many gallons per minute (GPM) your fixtures use at maximum. For example, a showerhead may run at 2.5 GPM, and a faucet may have a 0.75 GPM flow rate. The total is 3.0 GPM.
  • Determine how hot you want your fluid to be and compare it with your groundwater temperature. For example, you may like a temperature of 110 degrees Fahrenheit. However, your groundwater temperature is 60 degrees Fahrenheit.

Using the information above, you will need a tankless heater capable of raising the liquid temperature by 50 degrees Fahrenheit with a minimum flow rate of 3.0 GPM. Take note that the size computation presupposes you have someone using the shower and another person using the faucet simultaneously.

If you have two people using the shower simultaneously, you will need a tankless heater size capable of delivering 5 GPM (2.5 GPM shower x 2).

How to install an outdoor tankless water heater.

One should always check the local plumbing codes and guidelines before installing any outdoor tankless heater. One should also check the outdoor tankless unit for brand and model-specific installation instructions and prepare the materials and tools. Here are the steps.

  • Decide where to mount the outdoor tankless unit and turn off the main water supply line.
  • Cut a section of the water line to connect water fittings going to and from the best outdoor tankless unit.
  • Mount your new outdoor tankless heater and connect the water fittings and pipes. Ensure the main water line connects to the heater’s cold water intake port. Your water distribution line connects to the heater’s hot water outlet port.
  • If one is installing a gas-powered tankless unit, one needs to connect the gas pipe to the tankless heater. Tighten and secure all connections.
  • Turn on the main water supply line and check your work for leaks.
  • Turn on the gas and the outdoor tankless unit.
  • Set the water heater to the desired temperature.

How to keep an outdoor tankless water heater from freezing.

High-end outdoor tankless water heaters already have a built-in freeze protection feature. These products activate their antifreeze mechanisms when the temperature drops to a predetermined level. There is no need to take additional steps to prevent a frozen water heater item.

An excellent example of such a product is the Rinnai outdoor tankless water heater. This product features ceramic heaters integrated into its heat exchanger, water line, and internal parts. One can also see a similar freeze protection design in a Rheem outdoor electric tankless water heater.

If the product does not have this feature, one can observe the following measures:

  • Install your water heater in a warm place and away from cold drafts.
  • One should consider installing a recirculation system.
  • Run a small amount of hot water through your system.
  • Wrap the pipes and valves with a pipe heating cable with a built-in thermostat.
  • Drain and winterize your outdoor tankless water heater.

How often do you need to descale an outdoor tankless water heater?

One can descale a tankless water heater product every six to 24 months, depending on the groundwater hardness level in the house. The more hardness minerals present in your liquid, the more frequent the descaling is.

As such, if one lives in an area where groundwater hardness levels exceed 180 mg/L (equivalent to 180 ppm or 10.5 grains/gallon), one may have to descale the outdoor tankless unit as often as once every five to six months.

One may also have to descale the tankless unit once every 18 to 24 months if the groundwater hardness level is <60 PPM or <3.5 GPG.

We recommend installing a whole-house water softener if you have high groundwater hardness levels to ease the burden on your tankless water heater. A conditioner can also be an excellent option if you do not like frequent softener recharging.

Do outdoor tankless water heaters run out of hot water?

No, an outdoor tankless unit does not run out of hot liquid. However, it would be best to choose the correct size of a tankless heater.

For example, let us say you have an appliance with a maximum flow of 5 GPM and an 80-degree Fahrenheit temperature rise. This tankless water heater will never run out of hot liquid if you only use no more than 5 GPM at a time. If you use more than that, there is a chance the appliance may not provide you with your preferred temperature.


The best outdoor tankless water heater stands up to the elements without sacrificing liquid heating performance, energy efficiency, and cost savings. It can be a portable device you can bring to your adventures or a fixed appliance delivering consistently hot water to your home.

Getting the right tankless water heater for outdoor use makes perfect sense for people who want a safer yet equally efficient water heating system.

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