Close this search box.
Close this search box.

Rheem RTG-84XLN Review (January 2024) ~ Tankless Water Heaters

The Rheen Rtg-84xln At A Glance

Top Perk > Amazing Efficiency

Rheem RTG-84XLN 8.4 GPM Low NOx Outdoor Tankless Natural Gas Water Heater
View On Amazon

If you are tired of managing a heating unit that cannot keep up with all of your hot water demands, then there’s no better time to make a transition than now. The Rheem RTGH-84XLN Prestige tankless water heater is one of the best (second only to the 95XLN model) solution in the market today. This unit possess an amazing efficiency that quickly distinguishes from similar products in the same category. It comes with a massive water flow rate of 8.6 gallon per minute which ensures you get enough hot water for to meet all your demands. There are other amazing features this unit a good take, especially a 10-year warranty that puts your mind to rest. Believe it or not, you can never go wrong with a unit like the Rheem RTGH-84XLN.

  • 8.4/10
    Efficiency - 8.4/10
  • 9/10
    Ease of Use - 9/10
  • 9.4/10
    Value - 9.4/10
  • 9.4/10
    Features - 9.4/10

Rheem RTGH-84XLN

  • Cost: $$$
  • Model Number: RTGH-84XLN
  • Weight: 54 pounds
  • Size: 1 14 x 10 x 26 inches
  • Water Flow Rate: 8.6 gallon per minute (GPM)
  • Type of Unit: Outdoor
  • Fuel Type: Natural Gas
  • Energy factor: 0.84
  • Similar model: RTGH-95XLN
  • Warranty: Residential: Standard 10 year warranty



Beside an air heater, a water heater is probably the next most important commodity every household should have; why is why the market is flooded with various brands of tanked and tankless water heaters.

Ever since they came on the scene, tankless heaters have become the choice heaters for most homeowners. And it’s not difficult to see why. Besides featuring the latest technologies, these appliances tend to be more powerful and efficient than their traditional counterparts.

Unlike tanked heaters, they don’t require any storage tank and only use energy when they need to. They provide hot water on demand and don’t take up much space.

With so many tankless water heaters in the market, choosing one to meet your specific household needs can be a crapshoot. Luckily, we’ve done all the hardwork for you.

Today, we are going to review one of the best outdoor tankless heaters on the counter- the Rheem RTG-84XLN Tankless Water Heater. Before we delve in, let’s make one thing clear: the Rheem RTG-84XLN is a perfect choice if you are hoping to save from the high-end models. It is probably the best outdoor tankless water heater from Rheem. You can rely on its durability and capacity to deliver hot water on demand regardless of your family size.

This appliance comes with an impressive flow rate of 8.4 GPM at a 35 degree temperature rise with a consumption of 180k BTU, which makes it suitable for many (large to medium sized) households especially in the U.S. It has a rated efficiency that is superior to most of its competitors while its emissions are very low. This makes it pretty safe and environmentally friendly even though it’s meant to go outside the house. Don’t forget to check your pipe sizes before purchase or at better still, you can opt for new pipes.

At normal flow rate, the heater can deliver to up to 3 bathrooms simultaneously. This is not uncommon especially during winter when the weather is almost always chilly. If you are living in a house that has 3 bathrooms, then this product will make a great choice.

There are other amazing features this unit a good take, especially a 10-year warranty that puts your mind to rest. Believe it or not, you can never go wrong with a unit like the Rheem RTGH-95XLN.

We strongly believe that this product is one of the most powerful tankless heaters on the counter for whole house applications, which is why we have it listed in our choice of the best tankless heaters available in the market today.



The Rheem RTG-84XLN has a low fixture compatibility which enables it to supply hot water even in hot demand situations. The rated minimum and activation flow rates are 0.26 GPM and 0.40 GPM respectively. With such a configuration, you can be certain of an almost endless supply of hot water anytime you need it, no matter how long, a low water condition notwithstanding.

So no hurrying up your cooking, laundry, or bath, just because the water heater hasn’t got enough water. With the Rheem RTG-84XLN, you can have constant supply of hot water as long as you need it, and you don’t have to wait too long.

Interesting, this device can produce up to 8 gallons of water per minute or even more; which is more than enough for a family of 4 or 5.

The actual gallon capacity of the Rheem RTG-84XLN is 8.4GPM. So besides providing water for your whole family, this unit can also supply water to multiple faucets simultaneously. In order words, you can use 2 or 3 bathrooms at the same time without worrying about any fluctuation in the water flow.

Additionally, the internal heaters of this unit are configured in such a way that prevents cold from getting in. In order words, you won’t have to worry about the pipes getting blocked whenever the weather is chilly for long. WTM is used to guard the heat film wrap.

As expected with all Rheem models, the Rheem RTG-84XLN can be linked in up to 20 units. And is also configured to allowing water saving.

You can actually save up to 1,100 gallon of water in one year by reducing the water flow to the point where the temperature is equivalent to the set temperature of the unit.


One of the most fascinating things about the Rheem RTG-84XLN is that it allows you to be able to get hot water at first touch. However, this is not often the case with many tankless water heaters due to the time lag in activation rate. The burners of such systems only starts to heat after detecting flow and this consequently delays the water from coming out instantly.

One of the easiest ways you can avoid such delays is to pair up the unit with a re-circulation pump kit. Unfortunately, not every tankless heater in the market can seamlessly “blend in” with the kits currently on display in the market.

Luckily, the Rheem RTG-84XLN can be used with a re-circulation pump kit which allows you to enjoy the full performance of the appliance. This way, you will be able to get hot water the moment you open your faucet.

Another unique feature that makes the Rheem RTG-84XLN more efficient is that it gives you the ability to control the temperature of the water coming out.

This device comes with intelligent electronic controls which includes a digital display meter that allows you to set temperature to your preferred choice and adjust the water flow rate to make sure there’s no fluctuation in the water temperature. This ultimately resolves the sandwich problem of frequently switching the heater and waiting for cold water to get warm while you get frosty.

The Rheem RTG-84XLN is also equipped with all-copper heat exchanger to ensure greater heat transfer and exchanger.


The Rheem RTG-84XLN is equipped with a self-diagnostic system that reduces the hassle in installation and makes maintenance much easier. Like other outdoor tankless heaters, this unit doesn’t require venting. This should be a big plus for you especially when you also consider the fact you don’t have to worry about gas combustion since the heater is located outside the house.

If you have any DIY skill set at all, then you should find the Rheem RTG-84XLN pretty easy to install since no venting is required; although you may still encounter some problems along the way if you live in location that is frequently chilly. Anyway, that’s just by the way.

Generally, you shouldn’t spend much time hooking up this unit on your own if you are careful enough to follow every step on the instruction manual. Clear graphical illustrations are provided; though you can still see the tutorial video if you wish to.

But at the end of the day, you can hire a plumber for a few bucks if you have any doubt about taking up the set-up all by yourself. Perhaps working out the electrical, gas and water supplies during hook up may still require the involvement of an experienced person.

In terms of maintenance, this outdoor unit comes with a maintenance notice setting that alerts you whenever it’s time to do some servicing. And like every Rheem model it has 1/2″ gas line compatibility.

Space Saving

The usual conception about outdoor tankless heaters is that they use up space; though not as much as traditional hot water tank heaters. However, this is not the case with the Rheem RTG-84XLN tankless heater. This outdoor unit is pretty compact and requires less space. It doesn’t “stick out” too much like most similar brands.

Like we indicated earlier, you should consider hiring someone to hook up the system for you if you are not capable of resolving the supplies that will make the heater to function properly. Or else you can go ahead and become a pro!

Other Features

  • Digital remote control for your convenience
  • Freeze protection (though may not be able to withstand harsher climate)
  • Low emissions due to Ultra low NOx burner that is environmentally friendly
  • Sizing Software to take away the guess work
  • Capable of working at high altitude (up to 8,400 ft. elevation above sea level)


  • One of the most powerful tankless water heaters available
  • High energy factor at 0.83 (or 83% efficiency)
  • Strong water flow rate at 8.6 GPM
  • No ventilation is required
  • Endless supply of hot water on demand
  • Less expensive compared to other models from Rheem
  • Easy installation and maintenance
  • Compact size
  • Comes with safety features to prevent overheating
  • Environmentally friendly with ultra-low NOX emission
  • Comes with UMC-117 remote control


  • May not last as long in harsher climates; pipes can get frozen
  • Minerals can accumulate within the system which may reduce the lifespan

Frequently Ask Questions

Q: What warranty is available for this unit?
A: Warranty for Parts – 5 Years; Labour charges of repair for 1 Year; Heat Exchange warranty for 12 Years
Q: How many BTUs does this require?
A: 180,000btus.
Q: What is the difference between the RTG-84XN and RTG-84XLN?
A: XLN has ultra-low NOX emission, LN is low NOX. This is not necessarily a performance difference; just emission controls
Q: Can I install this in an attic?
A: No. This unit needs to be outside. If you want it in the attic, you have to get the interior model.
Q: Does the unit have a conversion kit for propane gas
A: No
Q: How efficient is this unit?
A: All models are high efficiency where the energy factor is 0.82 and higher and on demand water flow rate between 5.3 to high 9.5 GPM
Q: Will this still put out hot water during a power outage?
A: In the event of a power outage, the Rinnai Tankless Water Heater will not operate. However, it can operate with a battery backup system, which is available as third party accessories
Q: Does this unit come with everything I need to install it?
A: All of the basic fittings are included. You will need to have extra copper piping, solder and a torch on hand of course. Also you will have to order the safety valves.
Q: Where can I get an installation manual for review prior to purchasing?
A: Go to this link.
Q: Does this item come with the shut off valves?
” style=”fancy” icon=”arrow-circle-1″]A: No, it does not. You will have to order valves separately.
Q: What is highest temperature this unit can go?
: It goes up as far as 120F

Bottom Line

The Rheem RTGH-84XLN is a great product- one that is extremely efficient and will give you the best value for your money. It will deliver enough hot water to meet all your household needs and help you save money in the process. This unit can be used with up to 3 bathrooms and large appliances without noticeable fluctuation in water flow. You will always be covered even if two people are using the showers at the same time and you have to make supper hurriedly. The only downside you may notice with the Rheem RTGH-84XLN is its high price (which is expected considering its size and power) and the fact that it produces more noise. However, since it’s meant to be installed outside (though could can pose a problem), this shouldn’t be much of a concern. Overall, this unit is a good catch and will make a great purchase. You will surely benefit from having it around.


Water Divider

Related Posts