Brand Comparison

Best Rheem Tankless Water Heaters Reviewed

We have thoroughly reviewed the Rheem water heater range. Find out if this hot water system is best for your home.

by Matt Moran

Water heaters are an essential part of our daily lives. They provide us with the hot water we need to shower, cook, and clean every single day. Considering how much we rely on these systems, it makes sense to take the time to make sure you choose the right unit for your home.

Many water heater buyers opt for Rheem water heaters because Rheem is one of the best and most popular water heater brands on the market - but which of their water heaters is best? To help answer that question, we've reviewed the best tankless water heaters that Rheem has to offer so that you can find the unit that's perfect for your home.


Power Source

Flow Rate (GPM)

Uniform Energy Factor

Energy Star Certified


Check Price

Rheem RTG-95DVLN-1 Water Heaters, Gray

Natural Gas


0.93 UEF



Rheem RTE 9 3 GPM Electric Tankless Water...






Rheem 240V Heating Chamber RTEX-13...



0.998 UEF



Rheem RTG-84XLN Water TANKLESS Heater, Gray

Natural Gas


0.82 UEF



Rheem 18kW 240V Tankless Electric Water...



0.998 UEF



Rheem RTGH-95DVLP 9.5 GPM Indoor Direct Vent...

Liquid Propane


0.93 UEF



Rheem Mid-Efficiency 8.4 GPM Outdoor Liquid...

Liquid Propane


0.82 UEF



Rheem Water Heater Types

Rheem offers three different types of water heaters. These are:

Electric Tankless

Electric tankless water heaters are systems that heat water on-demand and are powered by electricity.

As with all tankless water heaters, there's no need for a storage tank. Instead, the water is heated as it travels from the source via the tankless system to your faucet.

Electric units are more energy efficient than gas units and don’t require ventilation to the outdoors, so you have more options for placement. We’ve reviewed the best electric tankless water heaters here.

Rheem Tankless Electric

Gas Tankless

Gas tankless systems heat water on-demand in a similar way to electric tankless units. The difference is that these units run on either propane or natural gas and that they require ventilation and can be trickier to install. They're also bigger, less energy efficient, and slightly cheaper to purchase than electric units. We've reviewed the best gas units in this post.

Hybrid Series

Hybrid hot water systems are also known as heat pump water heaters. Through a complicated technical process (that you probably don’t need to know about), they use electricity to move heat that’s already been generated around instead of creating more heat.

This makes them more energy efficient. When water demand is too high for this alone to be productive, they work like regular electric tankless systems and use electricity as fuel to heat the water.

Why Choose Rheem?

Rheem is one of the most well-known and respected water heater manufacturers out there, and for a good reason. They make the most extensive lineup of water heaters out of any brand, and most of their models get consistently good ratings that are well above average.

All of their models are:

  • Durable - they’re corrosion resistant and built with stainless steel heat exchangers
  • Energy efficient - Rheem has more water heaters with Energy Star ratings than any other brand
  • Low emissions - every Rheem water heater is designed to meet strict Low-NOx requirements

Standard Features of Rheem Units

Flow Rate

RV Showerhead

Various Rheem electric tankless water heater units have a wide range of GPM ratings, ranging from 0.9 to 8.8. The RTEX-04 has the lowest GPM and the RTEX-36 has the highest GPM.

GPM stands for Gallons per Minute and refers to how much water it can produce at any given time. The higher the GPM, the more hot water appliances you can run simultaneously. The average shower uses 2.1 GPM, and some units are capable of providing up to 8.8 GPM, making them suitable for large households.

Power Source

Different Rheem water heaters are powered by various power sources. These fuel sources include solar power, liquid propane, natural gas, and electricity. Each of these power sources has different pros and cons.

For example, liquid propane is portable, which makes it great for RVs, but it's less economical than other fuel sources. Solar-powered units can save you money on electricity, but the installation costs can be higher. Electricity is more efficient than gas, but gas tends to be cheaper.

Heating Output

The heating output of Rheem units is usually given in BTUs - British Thermal Units. The higher the BTU, the greater the thermal energy it can output in any single period. In other words, units with higher BTUs will heat your water more quickly and get it hotter.

The max BTU of any Rheem water heater is 199K, but different units have different BTU ratings, starting at 160K

Energy Efficiency

All Rheem water heaters are highly energy efficient and Energy Star compliant. Their range of tankless water heaters has efficiency ratings of up to 99.8%. That means that only 0.2% of the BTUs generated by these appliances is lost; the rest is transferred to the water to heat it up.

Indoor or Outdoor Use

Some water heaters are only suitable for indoor use, some are only suitable for outdoor use, and others still are suitable for both. Check the product details of any water heater before you buy it to make sure it's ideal for where you plan on installing/using it. Rheem has units for both indoor and outdoor use.

Installation Costs

The cost of professional installation service for a Rheem tankless water heater can range from between $600 and $1500.

The exact cost will depend on several factors, including whether you're installing it outdoors or indoors, the vent materials, and whether or not a gas line needs to be installed.

All Rheem Professional Series models have installation included in the package price, but these are only available at local dealers.

Rheem Tankless Water Heater Outdoors

Operating Cost

According to the US Department of Energy, water heater’s account for around 18% of the average households energy use. As such, a quick way to calculate the energy costs would be to assume it’s roughly one-fifth of your monthly energy bill. If you want to get more precise, you’d need to consider things like how often you plan on using it and the energy efficiency rating.

Expect to spend around $500 - $1000 per year on energy. On top of that, you’ll also need to factor in maintenance costs and repairs. Most water heater manufacturers will label their products with expected operating costs.

Safety Features

Some water heaters come with additional safety features that make them safer to use, like temperature gauges and auto shut-off functions. Consider what safety features each model you look at has when selecting your tankless water heater.


Most Rheem tankless water heaters come with a 5-year warranty period. This is reasonably good considering that some manufacturers offer much shorter warranty periods of just 1-year. Rheem water heaters tend to be fairly reliable and should last around 5 - 10 years in most cases. Their performance.

Unique Features of Rheem units

  • EcoNet Wifi Enabled
    Many Rheem units are EcoNet wifi enabled. This built-in wifi allows you to control the heater remotely via a smart device and app.
  • Built-in Condensate Neutralizer
    Rheem condensing water heaters come with built-in condensate neutralizers. These neutralize the pH of the condensate created by your water heater to make it safe for discharge.
  • Hot Start Programming
    Rheem water heaters are complete with hot start programming. This feature minimizes fluctuation in your water temperature so that the water doesn’t come out cold when you first turn it on.
  • Overheat Film Wrap
    The overheat film wrap included in Rheem units is a safety feature that automatically shuts the heating unit down if it overheats
  • Low Flow Activation
    Rheem water heaters activate at low flow rates.
  • Low NOx Emissions
    NOx stands for Nitrogen Oxide - a toxic greenhouse gas emitted by water heaters. All Rheem water heaters have low NOx emissions.
  • Recirculation Pump Kit-Ready
    Certain models of Rheem water heaters include recirculations pumps. These pumps circulate water that has already been heated back to the point of use so that you don’t have to wait as long for hot water.
  • Freeze Protection
    Some models also have freeze protection, which protects your water heater from freezing in very cold temperatures.

7 Best Rheem Tankless Water Heaters Reviewed

1. Rheem RTGH-95DVLN

Rheem RTG-95DVLN-1 Water Heaters, Gray
  • EcoNet is the Brains of Rheem Smart Air and...
  • Flow rate range from 0.26 GPM minimum to 9.5...
  • Temperature varies from 80F minimum to 140F...
  • Electronic ignition requires 200 watts, and...

The RTGH-95DVLN from Rheem’s Prestige line is our top pick the best overall (prestige) model.

It has a flow rate of 9.5 GPM, which is right at the top end of commercial water heater flow rates and more than enough for even the busiest households. You could run 4 showers in tandem, and this water heater would be able to handle it.l

It has a UEF (Uniform Energy Efficiency) rating of 0.93, and an EF of 0.96, which means it’s very energy efficient. It’s also efficient in water usage too. The included water saving setting decreases the flow rate until the water gets hot enough to reach the temperature setting. This feature alone should be able to save you up to 1,100 gallons of water each year.

It has some other cool features too that you only get on high-end models like this, like low flow activation (0.40 GPM), a recirculation pump, and hot start programming.

It's a natural gas unit made for indoor use, which means it will require proper ventilation. I'd recommend paying a professional to install this one as you don't want to mess up the ventilation and expose yourself to harmful gas byproducts.

"Hot water, forever!" says one customer on the Rheem website. "The good news: the water is hot and it just keeps going. The bad news: none, really. Maybe some inconvenience in installation."

2. Rheem RTE 9

Rheem RTE 9 3 GPM Electric Tankless Water...
  • On-unit temperature control
  • Standard 1/2" water connection
  • Rugged brass/copper heat exchanger
  • Modulating power

Next, we have the Rheem RTE 9 model. This unit is our runner up for the title of best Rheem water heater. I love it for three reasons: it’s compact, it’s portable, and it’s easy to set up.

With a flow rate of just 3 GPM, it's not the most powerful shower in the world, and wouldn't be sufficient for large households. However, it's perfect for point-of-use applications and can be the ideal unit for a man-cave, RV, or outdoor shower. The average shower uses around 2.5 GPM, so this one will be more than sufficient for these kinds of uses.

Bear in mind, though, that it doesn't have built-in freeze protection, so if you do want to use it for an outdoor shower, it will need to be in an enclosed, heated space or it might freeze up in cold temperatures.

It runs on electricity, which means it’s a little more energy efficient and a lot easier to install - you don’t need to worry about ventilation. It’s also very compact so it can fit in any small space. Not to mention, it’s very affordable.

If you’re just looking for something quick, simple, and affordable for a point-of-use application, you can’t go wrong with this unit!

Property manager Tony Hill gives the Rheem RTE 9 a 5-Star review. He says, "Four years ago a tenant in a rental property of mine was complaining that the kitchen faucet took way to long to run hot. The water heater was fine, just too far away from the kitchen. The RTE-9 seemed like a good solution to the problem at 3GPM so I ordered one and had it installed. It solved the problem perfectly and has been operating as advertised ever since."

3. Rheem RTEX-13 

Currently On Sale
Rheem 240V Heating Chamber RTEX-13...
  • External adjustable digital thermostatic...
  • Durable Copper immersion two heating...
  • Simple installation – 1/2 NPT adapters...
  • 99.8% energy efficient. External controls to...

This RTEX-13 water heater is from Rheem’s Professional Classic® tankless electric water heater series. If you’re looking to get the best value for money on your water heater purchase, this is the unit for you.

It has a flow rate of 4.8 GPM, which is right in that sweet spot of not too low and not more than you need. It’s perfect for single bathrooms and mid-sized households. I’ve used this product in a cottage with 1 bathroom, 1 kitchen sink, and 1 outdoor shower, and it never let me down.

"Professional Classic® tankless electric water heaters offer continuous hot water quick and on demand for single point-of-use or multiple applications." - Rheem

I also found that this water heater is consistent when it comes to temperature regulation. There's minimal temperature variation even when you're showering at a high temperature.

It comes with a water-saving shower head that has a 1.5 GPM flow rate, so you could technically run three of these at once with no problems. The shower head will help you conserve water too.

It runs on electricity and is very energy efficient, with a reported 99.8% efficiency. However, Rheem hasn't registered it for the Energy Star rating so it might not bag you the green rebate on your electricity bill. Still, you should be able to make substantial energy savings by switching over to this unit.

4. Rheem RTG-84XLN 

Rheem RTG-84XLN Water TANKLESS Heater, Gray
  • Natural Gas Tankless Water Heater
  • Outdoor
  • 8.4 gal/min. at 35-Degree Rise
  • UMC-117 remote control and 10-Feet of...

Next up we have the RTG-84XLN - the first outdoor water heater on this list. It’s outdoor-only, which means you have to put it outside, you can’t install it inside.

The benefits of an outdoor unit are three-fold:

First off, you don't need any additional venting. The unit is outside, so all potentially-dangerous gas byproducts get immediately blown away and don't get stuck in your home.

Secondly, it saves space in your home. You can install it on the outside instead of the inside so it won’t take up any floor space.

Thirdly, it saves you money. Not having to worry about ventilation reduces the cost and complexity of the installation. It can be installed in less than an hour, so it works out to be cheaper.

This unit also has an excellent flow rate of 8.4 GPM, which is good enough for large households with multiple bathrooms and has low NOx emissions, so it's kinder to the environment too.

It's a natural gas tankless water heater so it can be hooked up to your main gas line and heat your water on-demand. Like similar units from Rheem, it warms your water very quickly with minimal temperature variation.

One happy customer writes, "I'm so happy and glad our home came with the Tankless Water Heater. The Rheem W.H. is doing an excellent job. My home is 3500 sq. ft. We have not ran out of hot water even when other showers, washer, dishwasher, etc. are used at the same time. And, unlike the big, round, ugly water heaters, this unit is small, attractive, and unobtrusive. It's also easy to maintain. If you're able to get one for your home- go for it!"

5. Rheem RTEX-18

Currently On Sale
Rheem 18kW 240V Tankless Electric Water...
  • External digital thermostatic control with...
  • Most advanced self-modulation, adjust power...
  • Durable Copper immersion two heating...
  • Simple installation – bottom 3/4 inch NPT...

The RTEX-18 is another electric tankless water heater from Rheem’s Professional Classic® Series. It’s very similar to the RTEX-18 that we’ve already reviewed above, but a little more powerful.

The manufacturer’s product specification list this unit as having a max GPM of 7, which is higher than the RTEX-13's 4.8 GPM flow rate. It also has double the number of heating chambers. What does all this mean? This unit can heat more water more quickly. It's a better option for larger households.

Like all Classic Series water heaters, it’s very energy efficient, with a 99.8% reported efficiency rating. The in-built advanced self-modulation means it can adjust its power output based on hot water demand.

It also has a very nice, accurate LED digital thermostat displayed on the front, which makes it easy to monitor and control the temperature. It's easy to install, durable, and reliable.

The temperature of the water is always consistent unless you’re running an unrestricted bathtub faucet, in which case the water sometimes flow too quickly through the unit to heat up to the desired temperature. If you find that this starts happening, turn your faucet part way off to restrict the flow a little, and it should be fine.

6. Rheem RTGH-95DVLP 

Rheem RTGH-95DVLP 9.5 GPM Indoor Direct Vent...
  • 94-Percent Energy efficient with...
  • Intelligent electronic controls designed to...
  • Third party efficiency listed by AHRI
  • Up to 38-Feet of 3-Inch PVC Pipe or 5-Feet of...

The RTGH-95DVLP is, in my opinion, Rheem’s best indoor liquid propane condensing water heater. If you’re not hooked up to a gas line and want something a little more economical than an electric unit, a liquid propane heater like this one is the way to go.

It has the same GPM as our number one pick, 9.5. That flow rate is plenty enough for the largest households; you could run a bath and take 2 showers at the same time no problem.

One thing I love about this unit is how safe it is. It has a bunch of intelligent controls that have been included to make it as safe and efficient as possible. For example, it has an overheat film wrap that will shut off the heat exchanger were it to overheat to protect your home.

I also love the compact design. It’s a really small unit that could probably fit into a medicine cabinet. You might even be able to install it yourself, though I’d still recommend getting a plumber to make sure it gets installed safely.

One last thing worth mentioning is that this is a highly energy efficient device. It’s Energy Star certified and has a UEF of 0.93.

7. Rheem RTG-84XLP-1 

Rheem Mid-Efficiency 8.4 GPM Outdoor Liquid...
  • Exclusive Water Savings technology conserving...
  • 157, 000 BTU (gas consumed per hour)
  • Exclusive Hot Start Programming minimizes...
  • Recirculation pump ready kit ready.8.4...

The RTG-84XLP-1 is another excellent liquid propane water heater. The main difference between this one and the unit above is that this one can be installed outdoors.

It’s an outdoor propane unit that is built to withstand cold climates. The freeze protection means it will hold up well in temperatures as low as -30 degrees. Anything over that and it might freeze, but realistically, you’d have to live in the Arctic for it to get that cold, so you should be fine!

Two features I like about this unit are the hot start programming and the recirculation pump. The hot start programming minimizes cold water bursts by reducing the flow rate until the water has reached the desired temperature. This means that you don’t have to worry about that horrible burst of cold water when you first switch your shower on in the morning!

The recirculation pump means that it will recycle the water that’s already been heated through your plumbing to improve efficiency. This unit also has other exclusive water saving tech built in that can save you over 1,000 gallons of water every year.

All in all, it's a great outdoor propane water heater that I'd recommend if you don't want an electric or natural gas unit.

Comparisons with Other Brands

Rheem vs Rinnai Whole House

Both Rheem and Rinnai are well-respected names in the water heater industry. The quality of products produced by both of these brands is superb, and it's difficult to say which is the best, overall.

Rheem water heaters tend to be comparatively more affordable than Rinnai and overall better value for money. For example, on similarly priced models, Rheem offers a 10-year warranty on heat exchangers compared to Rinnai, who only provide a 5-year warranty.

Rheem vs. Rinnai Tankless

Both Rheem and Rinnai have very similar max flow rates in their line of tankless water heaters. The top Rinnai tankless water heater flow rate is 9GPM, while Rheem's is 8.8GPM - an almost negligible difference. They also both have a range of tankless units suitable for indoor and outdoor use, and which use a variety of different fuel sources.

Our favorite tankless water heaters in every category can be found in our full guide, here.

Installation of Rheem Hot Water System

The costs of paying a professional to install your Rheem hot water system can range from between $500 and $1500. Rheem recommends having their units installed professionally to maximize their lifespan and make sure they're safe for operation.

You can purchase a unit from their Professional Line series if you want the cost of installation to be included in the package.

If you’d prefer to have a go at installing it yourself, the video below provides a guide on how to go about it, but be careful as it can be dangerous if you’re not a licensed professional.

Rheem Water Heater Maintenance

To keep your Rheem water heater in top condition and increase its longevity, you should carry out routine maintenance. Some of these tasks you can do yourself, but it's usually better to call a professional plumber and have them do it for you.

Here are some water heater maintenance tips:

  • Drain the water tank and clean out the sediment around once per year.
  • Check the pressure release valve once a year and replace it if necessary
  • Inspect the anode rod every third year and replace it if necessary

Where to Buy Rheem Heaters?

Rheem water heaters can be purchased via:

  • 1
  • 2
    The official Rheem website
  • 3
    Local licensed Rheem dealerships
  • 4
    Amazon home services

You can often get better value-for-money through Amazon, but it's worth shopping around and comparing your options. If you're interested in purchasing any of the products we've reviewed in this article, click the product name in the list above to view the Amazon listing.

Using Rheem Warranty Effectively

Rheem water heaters come with varying limited warranty periods, usually between five to 12 years.

This will typically cover you for the cost and transportation of replacement components and parts due to manufacturing errors for a number of years. For certain products, labor will also be covered in your warranty for a shorter time.

Once you’ve purchased your Rheem water heater, you should verify the warranty here; you’ll need to have your serial number to hand. You can also register your product on this page if you want to extend your warranty.


To claim or request your warranty service, you need to contact your local Rheem Pro. Again, they’ll need you to give them your serial number, so make sure you have this to hand when you call.

Rheem Replacement Parts

You may find that in the future, you need to replace one of the parts on your Rheem water heater, like the drain valve, thermostat, or anode rod. These parts can become damaged or worn over time.

If so, you can buy replacement parts via the Rheem website, local Rheem dealerships, Amazon, eBay, or other appliance stores.

People also Ask (FAQs)

What is the history of the Rheem company?

The Rheem Manufacturing company has been around for nearly a century. It started back in the 1920s as a galvanizing plant based in San Francisco, California, and began to manufacture and distribute water heaters in the 1930s.

How long are Rheem units expected to last?

Around 8-12 years, depending on the frequency of use and the quality of water and installation.

How do you flush or drain a Rheem hot water heater unit?

This guide provides step-by-step instructions on flushing a Rheem hot water heater.

How do you winterize a Rheem unit?

I’d recommend watching this video for instructions on winterizing hot water heaters.

How do I adjust the temperature on my system?

You can control the temperature by turning the thermostat dial/gas control valve. More detailed instructions are available here.

What is the price range of the products on our list?

We’ve tried to include an option for every budget, so products on this list range from between $300 and $1800. Prices vary online from day to day so always check out the latest listings and deals.


That concludes our Rheem tankless water heater reviews and comparison guide. Before we wrap up, I want to once again recommend the Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater - it’s the best choice if you’re looking for an efficient, powerful, durable gas unit. 

Matt is a freelance writer, English graduate, & keen traveler from the UK. As a specialist plumbing expert, he enjoys writing about everything there has to do with at-home plumbing products & related problems. When he isn’t writing, he’s usually drinking coffee or planning his next adventure. In his spare time, he also runs his own blog all about digital nomad life.