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Your Guide to Home Heating and Cooling Systems

Last Updated on January 21, 2022

Rheem RTE 13 Review

Rheem 240V Heating Chamber RTE-13 Residential Tankless Water Heater​

Continuing our in-depth reviews of Rheem tankless water heaters, we’re examining the Rheem RTE 13. It’s a fully electric, viable option for small households.

If you’re upgrading from a traditional (tank) water heater, you’ll be impressed with its small size, energy efficiency, and constant supply of hot water. If you’ve already had the pleasure of owning a tankless water heater, you’ll enjoy how easy the Rheem RTE 13 is to install.

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Is It Worth Your Money?

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The Rheem RTE 13 seems expensive at first glance, but the initial investment is worth the benefit of the energy it will save you. It will adequately meet the needs of most small families with the ability to supply one shower and a dishwasher or washing machine simultaneously.

It’s easy to install with electrical and plumbing connections only and is compact enough to install under a sink or in a cabinet. Adjust the temperature control from 80-140-degrees Fahrenheit.

You won’t need to perform much maintenance on the Rheem RTE 13, but this is one tankless water heater that we wish came with a longer warranty. The company ensures the heat exchanger for 10 years, but the remainder of the parts for only one. In addition, the warranty is only valid if an approved technician installs the unit.

Detailed Review & Breakdown

The Rheem RTE 13 provides all the benefits of an electric tankless water heater, but the cost and water capacity limitations might make it unsuitable for some homes. Here are the details that you’ll want to know before buying this unit.




The Rheem RTE 13 uses electricity only to heat up to 4 gallons of hot water per minute. That means that you could run two showers, or a shower, a dishwasher, and a faucet all at the same time without running out of hot water. And it only draws power when you turn on a hot water faucet, saving you money in energy costs over traditional tanked water heaters and even over natural gas or propane tankless water heaters.

You can also adjust the temperature output on the Rheem RTE 13. You can lower it 80-degrees or raise it high as 140-degrees. For most household applications, you can keep the water heater set lower to conserve energy and bump it up to 105-degrees or so for your showers. If you’re filling a Jacuzzi or hot tub, set it to 140-degrees and then bring it back down.

The Rheem RTE 13 is one of the smallest tankless water heaters you can buy. It measures less than a foot in any direction. With that small of size and infrequent maintenance needs, you can install it under the bathroom or kitchen sink or in a linen closet to completely hide it out of the way.

This all-electric tankless water heater is perfect, and approved for, manufactured and mobile homes. In many cases, it will be an upgrade to the tankless water previously installed.


The Rheem RTE 13 tankless water heater is an extremely small, lightweight unit that uses as much energy as your oven or dryer. Unlike other tankless water heaters, it is powered by electricity only without the use of natural gas or propane. It consumes energy only when you turn the hot water on, saving you energy costs.The</spanheem RTE 13 is so small, it can be considered a point-of-use water heater.


Ease of Use & Reliability

The Rheem RTE 13 is extremely easy to use and maintain. There is a knob to adjust temperature control, and that’s it. There are no other settings you’ll need to worry about.

If you have hard water, you will need to flush the unit once a year to remove mineral deposits. Simply turn off your cold water valve, detach the pipe from the water heater, and turn on your hot water, letting the Rheem pull from a bucket of water and vinegar solution. When empty, turn off the hot water and reattach the cold water pipe.

While you should be able to expect a tankless water heater to last 20 years or more, remember that Rheem does not provide a warranty on any of the parts if you install the unit yourself. It must be installed by a certified professional. If it is not installed by an approved technician, you will need to pay for any parts that fail on the water heater or replace the entire unit.

You can install the Rheem RTE 13 anywhere in your house. Just be aware that it needs to connect to both your electricity and plumbing and like traditional water heaters, the further the unit is away from the faucet, the longer it will take for the hot water to reach you.

If you want to use the temperature control setting on a frequent basis, install the unit in an easy to reach location. You might not want to crouch down under your sink every time you take a shower.


Any Other Criteria?

Be comfortable working with electricity, plumbing, and drywall if you plan to do the job yourself. The unit requires 240 volts of electricity, so remember to exercise caution at all times. Also, keep in mind that doing the job yourself voids any warranty on the unit.

If you are going to install the Rheem RTE 13 by yourself, purchase the valve kit to ensure you have all of the necessary fittings near at hand.



The Rheem RTE 13 is currently available for less than $500, plus approximately $10 shipping. You’ll also need an installation kit (less than $60). Though easier to install than gas or propane water heaters, you might want to hire a professional for the job (~$1200).

Is This The Tankless Water Heater For You?

Who Is This For? As a low volume water heater, the Rheem RTE 13 is designed for households of 1-3. With a maximum flow rate of 4 gallons per minute, it will reliably supply one shower and a washing machine at the same time.

Its compact size makes it ideal for installing it under a sink in the bathroom or kitchen. If the layout of your home separates the bathroom and kitchen by a long distance, install the water heater in a cabinet or closet between the two to minimize travel time for the hot water supply to either location.

Our Opinion

We like this fully-electric model for small or low-volume households. We like that it saves on energy. We like the size. We do not like that the company provides no warranty on the unit when the owner installs it. The installation is not complicated. Most handy persons should be able to perform the task without much of a problem with this tankless water heater.

Other Options Worth Looking At:

If you’re not sure if the Rheem RTE 13’s 4 gallons per minute will meet your needs, consider purchasing the Rheem RTEX-18, which provides 7 gallons of hot water per minute. You could also look into a Rinnai natural gas or propane unit.

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