Top 6 Best Outdoor Tankless Water Heaters (2020 Review)

Interested in finding the best outdoor tankless water heater?

Tankless water heaters that are installed outdoors make an easier install (no flue), and it also saves space.

In this guide, I will go over...

  • My #1 top pick for the best outdoor tankless water heater
  • How to maintain a outdoor heater
  • Tips on picking the best outdoor unit

Let's get started with this guide!

top best rated outdoor tankless water heater reviews

My Overall #1 Rated Pick

top best rated outdoor tankless water heater reviews rinnai
  • Up to 9.4-gpm
  • 82% Efficient
  • Up to 6 fixtures at once
  • Natural gas
  • WiFi connected for control

My overall top pick for the best outdoor tankless water heater goes to the Rinnai RL Series HE+. This premium tankless unit can handle up to 9.4-gpm (varies by groundwater temp) and can handle up to 6 plumbing fixtures at once. It can also be WiFi connected for control and monitoring.

ImageProduct
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Rinnai RL Series HE+
  • 6 Fixtures
  • Up to 9.4-gpm
  • WiFi Connected
  • 6 Fixtures
  • Up to 9.4-gpm
  • WiFi Connected
View on Amazon
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Rheem RTG-84XLN-1
  • Up To 3 Baths
  • Hot Start Tech
  • Outdoor Install
  • Up To 3 Baths
  • Hot Start Tech
  • Outdoor Install
View on Amazon
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Noritz NR500D
  • Up To 5-gpm
  • High Efficiency
  • Easy Part Replacements
  • Up To 5-gpm
  • High Efficiency
  • Easy Part Replacements
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Rinnai RU98EN
  • Up to 9.8-gpm
  • Mid to Large Homes
  • 199k-btu
  • Up to 9.8-gpm
  • Mid to Large Homes
  • 199k-btu
View on Amazon
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Eccotemp 20H
  • Up to 6-gpm
  • 3 Fixtures
  • Smart Adjust Tech
  • Up to 6-gpm
  • 3 Fixtures
  • Smart Adjust Tech
View on Amazon

Top 5 Best Outdoor Tankless Water Heaters

My top picks for the best range outdoor tankless water heaters are high quality, efficient, and can handle outdoor installations — standing up to rain and snow. These top rated tankless heaters range from 2-gpm and all the way up to 9.5-gpm, and a low of 150,000-btu and as high as 200,000-btu.

  1. Rinnai RL Series HE+ (Top Pick)

  2. Rheem RTG-84XLN-1

  3. Noritz NR500D

  4. Rinnai RU98EN 

  5. Eccotemp 20H 

What Is An Outdoor Tankless Water Heater?

An outdoor tankless water heater is a device that will heat water as it passes through and is rated for an outdoor installation.

The main benefit of tankless water heaters is that they provide continuous hot water unlike the standard hot water tank. Tankless water heaters are also highly efficient, ranging from 80% to 95% efficient.

Tankless water heaters use specialized (usually copper) heat exchangers that will instantly heat up the water as it goes through the unit, and exactly when you need it. And when a tankless water heater is installed outdoors, no vent pipes or flues are necessary — because it's already outdoors.

The usual places to install one of these units is in a basement or the garage. But some tankless heaters are outdoor rated which means they are designed to withstand the elements and freezing temperatures.

Read Also: What Are The Best Point-Of-Use Tankless Water Heaters?

Freeze Potential

Depending on where you are located (usually in the southern portion of the U.S.) you will want to determine what freezing temperature your unit can withstand.

It's also a good idea to wrap the exterior water piping with at minimum insulation or even heat tape—to prevent bursted pipes.

When you install a tankless unit outdoors, it can save some space which you would otherwise use in your garage or basement.

Read Also: How To Take An Instant Hot Water Shower?

Condensing Vs. Non-Condensing

The two main types of outdoor tankless water heaters are condensing and non-condensing.

Condensing tankless units are generally more expensive and are about 10% more efficient. There is extra piping required with condensing tankless heaters because the condensate (water) needs to be drained away from the home's foundation.

Condensing tankless water heaters get that extra efficiency by removing condensate from the exhaust gases and getting that extra energy that non-condensing units don't get.

Read Also: What Are The Best Point-Of-Use Tankless Water Heaters?

top best rated outdoor tankless water heater reviews (1)

Maintenance

There is one important maintenance requirement with outdoor tankless water heaters if you have hard water.

Usually once a year or every few years (depending on the size of your household) you will have to flush the heater with a descaling agent to remove the buildup of mineral deposits.

Read Also: What Are The Best Grundfos Hot Water Recirculating Pumps?

Reviews of The Best Outdoor Tankless Water Heaters

Here are my reviews of the top picks for best outdoor tankless waters with their pros and cons. Check it out below...

My hands down #1 top pick goes to the Rinnai HE+. It is a premium tankless water heater and great for outdoor installations.

The HE+ can handle up to 9.4-gpm (varies by groundwater temperature) and is 82% efficient.

This outdoor-installed tankless heater can be installed in non-traditional locations like attics and crawlspaces.

It is also capable of being connected to WiFi so you can control and moniter hot water usage. The Rinnai HE+ can handle up to 6 home fixtures.

  • 6 fixtures
  • WiFi connected
  • Natural gas
  • Up to 9.4-gpm
  • Sensitive to breakdowns
  • Costly to repair (Rinnai certified only)

This Rheem unit is a high quality gas-fired tankless water heater (installed outdoors). It is rated at 157k-btu and is recommended for homes with three bathrooms or less (~82% efficient).

The Rheem RTG has a hot start programming so there is never a cold water burst because it is in a constant ready state.

This tankless unit can be installed anywhere outdoors including nonstandard locations such as attics and crawlspaces (no venting required). It also has a low flow activation with a minimum flow rate of 0.26-gpm.

  • Up to 3 bathrooms
  • Outdoor installation
  • Hot start programming
  • Pricey
  • Difficult install

The Noritz NR500D is a high efficiency tankless water heater that can be installed outside your home. This gas-fired tankless unit will provide instant hot water at a rate of 5-gpm.

Noritz introduced the first electronically controlled tankless heater all the way back in 1981. A valve kit is required for installation for the outdoors and is not included (part# IK-WV-200-1-XX-LF).

The Noritz NR500D runs at a high efficiency and can save a significant amount of energy and water over a year. Most parts are easily attainable at plumbing supply shops.

The Noritz tankless heater produces very low levels of NOx (nitrogen oxides).

  • Up to 5-gpm
  • High efficiency
  • Easy to obtain parts
  • Separate valve kit required

The Rinnai RU98EN is an ultra efficient tankless water heater.

It runs at 9.8-gpm and is suitable for medium to large sized homes, and is rated at 199k-btu. This outdoor installed heater meets California and Texas NOx emission standards.

If you want a high efficiency condensing tankless heater, then this is a great option by Rinnai.

It is gas-fired, imported, and has a max energy factor of 0.93.

  • Up to 9.8-gpm
  • Outdoor install
  • For mid to large sized homes
  • 199k-btu
  • Poor customer service
  • Costly to repair (Rinnai techs only)

The eccotemp 20H is a high quality outdoor-installed tankless water heater. It is rated at 6-gpm and with a 150k-btu...it is suitable for almost any sized home.

The 20H will provide instant hot water for up 3 applications at anytime — such as two showers and one dishwasher.

It's computerized controller has smart adjust technology with high performance processing for optimal hot water delivery. The efficiency is 83%  which means it is highly efficient and will save money.

  • Up to 6-gpm and 150k-btu
  • 3 applications at one time
  • Smart adjust technology
  • Low GPM

The Noritz NR66OD is a high quality outdoor tankless water heater.

It is rated at 6.5-gpm, 140k-btu, and uses natural gas in outdoor applications. This high efficiency heater by Noritz has low NOx emissions.

However, it does require a separate valve kit for installation and it is not included.

The Nortiz heater is a great compact heater which can be installed outdoors and save space.

  • 6.5-gpm
  • High efficiency
  • Low NOx emissions
  • Outdoor install
  • Separate valve kit required

My #1 Top Pick: Rinnai RL Series HE+

My #1 top pick for the best outdoor tankless water heater goes to the Rinnai HE+. Here's why...

#1. High GPM

This outdoor unit can handle up to 9.4-gpm (varies by groundwater temp) which is more than double capacity of most other outdoor tankless heaters.

#2. WiFi Connection

This tankless water heater can be connected to wifi for remote monitoring and control.

#3. Six Fixtures

This efficient tankless water heater can supply instant hot water up to 6 plumbing fixtures at the same time. No more hot water fights.

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Arie Van Tuijl

Arie Van Tuijl

Arie is the founder of Home Inspector Secrets, an online resource dedicated to helping people understand how homes work. He is a licensed home inspector in two U.S states and owns a residential and commercial inspection company (read his full bio on the About page). To ask Arie a question, please use the comment box at the bottom of the relevant article.

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