best outdoor tankless water heater

best outdoor tankless water heater

Finding the best outdoor tankless water heater for your home can be a daunting task. But this guide will help you through the process by giving you our top 5 picks from some of the top manufacturers in the business.

Outdoor tankless water heaters are an excellent choice. They save space, don’t require venting, and are easier and less expensive to install. If you’re looking to buy a tankless water heater, you should definitely consider purchasing an outside model.

Top 5 Best Outdoor Tankless Water Heaters

Each of the outdoor water heaters on our list are designed for whole house use by the top manufacturers in the industry. 

Best Overall: Rinnai RU199eN Outdoor Tankless Water Heater

The Rinnai RU199eN is our top pick and we consider it to be the best outdoor tankless water heater you can buy.

This condensing tankless is capable of delivering up to 11 GPM (gallons per minute), and can support up to 7 appliances. With its powerful output, the Rinnai RU199eN is perfect for families with high hot water needs.

The RU199eN is part of Rinnai’s Super High Efficiency Plus line-up. It’s Energy Star compliant and has an EF (Energy Factor) rating of 0.96.

It’s also Wi-Fi capable so you can download the Rinnai app to your phone and adjust, monitor, and troubleshoot your unit from remote locations or the comfort of your couch.

Rinnai is known for building top-performing tankless water heaters, and they typically have multiple options for each model. The RU Model Series offers both indoor and outdoor tankless units.

The RU199eN is designed for Natural Gas, but Rinnai also offers the RU199eP which uses Propane. And if 11 GPM is too much hot water for your household, there are three smaller sizes starting at 7 GPM.

With a 15-year warranty on the heat exchanger, 5-years on parts, and 1-year labor it’s hard to go wrong on this quality outdoor tankless water heater.

The RU199eN can deliver up to 11 GPM of hot water, has a maximum BTU input of 199,000, and an Energy Factor Rating of .96.

Rheem RTG-95XLN-1 Outdoor Tankless Water Heater

The Rheem RTG-95XLN-1 is a non-condensing outdoor tankless water heater that’s capable of delivering up to 9.5 GPM of hot water, and can support 3 to 4 bathrooms.

The RTG-95XLN-1 is part of Rheem’s Mid Efficiency line-up which has an Energy Efficiency rating of 0.81. It has an all copper heat exchanger, and an Ultra Low NOx emissions burner.

Add the Tankless EcoNet Accessory Kit and you’ll be able to connect to the EcoNet mobile app and receive alerts and maintenance reminders, gas and water usage reports, and even integrate with Smart Home Systems.

The RTG-95XLN-1 is designed for Natural Gas, however Rheem offers the same unit that burns Propane (RTG-95XLP-1).

Rheem tankless water heaters are a popular choice for homeowners who are looking for a quality product that’s more budget friendly than Rinnai.

They offer a 12-year warranty on the heat exchanger, 5-years on parts, and 1-year labor, however, professional installation is required.

The RTG-95XLN-1 can deliver up to 8.5 GPM of hot water, has a maximum BTU input of 199,900, and an Energy Factor rating of .81.

Nortiz NRC661-OD-NG Outdoor Tankless Water Heater

Another excellent choice is the Nortiz NRC661-OD-NG. Capable of delivering up to 6.6 GPM of hot water, this condensing outdoor tankless water heater falls into Nortiz’s ecoTough High-Efficiency Series.

‎The NRC661-OD-NG uses natural gas and sports a high-efficiency low NOx Eco-Burner to reduce emissions. And with a thermal efficiency rating of 93%, nearly all of the fuel will be used to heat the water.

The durable steel casing with a polyester coating is designed to provide plenty of protection from the elements. The maximum flow rate of 6.6 GPM should be able to handle an average household hot water demand.

This is a no-nonsense tankless without a lot of bells-and-whistles like Wi-Fi. However, it’s a solid performer and a great choice from a leader in the tankless world. Nortiz is known for manufacturing quality, long-lasting, and energy efficient tankless water heaters.

Nortiz offers a 12-year warranty on the heat exchanger, 5-years parts, and 1-year labor.

The ‎NRC661-OD-NG can deliver up to 5 GPM of hot water, has a maximum BTU input of 120,000, and an Energy Factor rating of .93.

Rheem RTGH-90XLP-2 Outdoor Tankless Water Heater

The RTGH-90XLP-2 is another outstanding outdoor tankless water heater by Rheem. Capable of delivering up to 9.0 GPM of hot water, this condensing unit is part of Rheem’s Prestige Collection.

‎The Rheem RTGH-90XLP-2 burns liquid propane and can handle up to 3 to 4 bathrooms. However, there’s also a natural gas model available, as well as several different sizing options.

With an Ultra Low NOx burner, built-in condensate neutralizer, and the stainless steel and copper construction, this outdoor tankless is designed for both longevity and performance.

Download Rheem’s exclusive EcoNet app and you’ll be able to monitor the unit’s efficiency and performance. You’ll even receive gas and water usage reports. 

Rheem offers a 12-year warranty on the heat exchanger, 5-years parts, and 1-year labor.

The ‎RTGH-90XLP-2 can deliver up to 9 GPM of hot water, has a maximum BTU input of 180,000, and an Energy Factor rating of .93.

Rinnai V53Den Outdoor Tankless Water Heater

Part of Rinnai’s V Model Series, the V53DeN can deliver up to 5.3 GPM of hot water, making it ideal for small to medium sized homes. The V53DeN is a non-condensing, Natural Gas tankless, but there’s also a Propane model available.

‎This outdoor tankless water heater is also mobile (manufactured) home certified, and is approved for altitudes up to 10,200 ft.

The Rinnai V53DeN is a no-nonsense tankless unit without all the  bells and whistles. However, don’t let that deter you, if you’re looking for a budget-friendly outdoor tankless water heater from a reputable manufacturer, this is an excellent choice.

Rinnai offers a 10-year warranty on the heat exchanger, 5-years parts, and 1-year labor.

The ‎V53DeN can deliver up to 5.3 GPM of hot water, has a maximum BTU input of 120,000, and an Energy Factor rating of .81.

Buyers Guide

Here are a few things to consider when purchasing an outdoor tankless water heater. However, we highly recommend reading our complete tankless water heater buyers guide as it goes into deeper detail.

> > Read Our Tankless Water Heater Buyers Guide HERE < <

Condensing vs Non-Condensing

All gas tankless water heaters produce exhaust. One of the advantages of an outdoor tankless system is the lack of venting since the unit is already outside. 

However, that doesn’t mean that you should consider how the tankless unit handles it’s combustion exhaust. Let’s take a closer look at each type:


Non-condensing tankless water heaters are less expensive to purchase, but also less energy efficient.

On average, non-condensing systems will deliver an EF rating in the low-to-mid 80% range. 

The exhaust is highly acidic and would require expensive stainless steel venting which is corrosive-resistant if it was an inside model.


Condensing tankless water heaters are more expensive to purchase, but they are also more energy efficient. In fact, you’ll generally see a 10% increase in energy efficiency with condensing models. 

The heat is extracted from the exhaust before its released from the appliance. The heat from the exhaust is actually used to heat the water, which allows condensing systems to achieve mid 90% energy efficiency scores.

Energy Efficiency

All water heaters use an Energy Factor (EF) to measure the units overall efficiency. It’s an easy way for you to determine, at a glance, how energy efficient the appliance will operate.

The EF rating is an indication of the amount of hot water produced by each single unit of fuel the tankless consumes.

Tankless water heaters with a higher EF rating will be more energy efficient. In other words, more of the fuel will go into heating the water.

Although, keep in mind that as your household’s hot water demands increase, the tankless water heater’s efficiency and savings will decrease.

Finding the Right Size

Purchasing the right sized tankless for your household’s hot water needs is critical. There’s no need to purchase a model that can produce 11 GPM if you only need a maximum of 5 GPM during your peak hour.

And the reverse is true too. If your tankless can’t produce enough hot water when you need it, you simply won’t be a happy camper. Nobody likes cold or lukewarm showers!

Taking the time to calculate your hot water needs can be a daunting task, but we have an easy tool you can use that even takes into account the ground temperature water of where you live. 

Tankless Water Heater Sizing Calculator

Use our  Sizing Calculator to determine your: 

Flow Rate  and Temperature Rise

Freeze Protection

Even tankless water heaters inside can freeze, but outside units are especially prone to cold weather.

Many outdoor tankless water heaters have built in freeze protection that’ll cycle on when the temperature drops, and there are also precautions you can take, such as wrapping pipes with a heated water pipe cable and insulation.

In some situations you may want to drain your tankless to prevent it from freezing. Read our article on how to care for your tankless water heater in cold weather HERE. 


When properly maintained, a tankless water heater can last 20 years.

To keep your unit operating in peak form we highly recommend hiring a professional to perform an annual inspection.

He’ll be able to inspect your unit’s operation and make adjustments as needed, and show you how to properly flush the tankless to remove scale build-up. Flushing is a critical maintenance task that needs to be done on a regular basis.

We recommend reading the following articles:

Frequently Asked Questions

Here are a few frequently asked questions regarding outdoor tankless water heaters:

Can a Tankless Water Heater Go Outside?

Yes, a tankless water heater can be installed outside if it’s designed for outdoor installation. These water heaters are built to withstand the weather and are easier to install since they don’t require venting.

Never attempt to install an indoor tankless water heater outside, or an outdoor tankless water heater inside.

Can a Propane Tankless Water Heater Be Installed Outside?

Absolutely, provided it’s an outdoor tankless water heater. An indoor tankless water heater should never be installed outside.

Since Natural Gas is not available in all areas, most manufacturers offer Natural Gas and Propane versions of their tankless water heaters. In addition, manufacturers frequently offer indoor and outdoor versions within the same model line-up.

What is the Best Brand of Tankless Hot Water Heater?

It’s hard to go wrong with a Rinnai or Rheem tankless water heater. Both company’s have been building water heaters for a very long time and are leaders in the industry.

Nortiz and Navien are also top performing tankless water heaters worth considering.

We highly recommend checking the manufacturer’s website for trained service personnel. Once installed, you’ll need to make sure you have access to an authorized technician who’ll be able to service and diagnose problems. Some brands have better service coverage than others, it’s always a good idea to make sure the brand you choose has multiple options for service in your area. 

How Much Does it Cost to Install a Tankless Water Heater Outside?

A good starting estimate is around $600, but there are a lot of factors to consider that could adjust the cost.

Outdoor tankless water heaters are less expensive to install than indoor models because they don’t require venting, however you’ll want to install freeze protection to protect them in the cold weather.

In most cases, replacing a tankless water heater in an existing location will be less expensive than installing a new one. 

Is it Better to Have an Indoor or Outdoor Tankless Water Heater?

Outdoor tankless water heaters are a great choice and have many advantages over indoor models. However, there are a few things you should consider because they are not suitable for every area.

You won’t need to worry about venting or providing enough space for combustion with an outdoor tankless. However, if you live in an area that tends to see a lot of storms or is just generally windy, an indoor unit would be a better choice.

There’s also a risk of vandalism with outdoor units since they’re fully exposed on the exterior of your house. 

With that said, if you live in an area where an outdoor tankless water heater is an option, it’s hard to go wrong. 

How Do I Protect My Outside Tankless Water Heater from Freezing?

Outdoor tankless water heaters don’t have the same protection that indoor models have from cold weather. Although they typically have some freeze protection methods built-in, you’ll need to give your unit a helping hand.

Here are a few ways to prevent freezing:

  • Installing freeze protection solenoid valves will shut down the incoming water and drain the tank should there be a power outage.
  • Wrapping the exposed water pipes with a water pipe heat cable and insulation will protect the pipes to the tankless.
  • Running a trickle of water will keep water flowing through the unit.

If you own an outdoor tankless water heater it’s a best practice to have a winter plan prior to the storm hitting. We highly recommend reading our article on caring for your tankless water heater during winter weather HERE.

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BY M. Kogan

Hello, I am Marcio. I am an architect and designer, alma mater is Mackenzie. Retired in theory, but an architect never retires completely. Along with architectural projects, I am a filmmaker and have completed some short documentaries. Filmmaking and design are my passions. In HomeQN I write about home decoration and foundations. The goal is to teach homeowners to DYI as much as possible, and when this is not possible, enable them through knowledge, to evaluate service quotations and choose the best service technicians.

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