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Rheem RTEX-08 Electric Tankless Water Heater Review

by | Jan 12, 2017 | Plumbing Product Reviews, Water Heaters


Rheem 8kW 240V Tankless Electric Water Heater

Rheem RTEX-08 Electric Tankless Water Heater

Tankless water heaters come and go. Some models are too expensive for the average homeowner to afford. Others lack the efficiency required to make them desirable. Still others are genuinely decent products that simply do not catch on with the masses. Rheem is one of the rare brands that has managed to defy these expectations. Not only are their products affordable, but they also produce solid tankless water heaters that, for some consumers, can slice their monthly energy consumption in half.

The latest addition to the Rheem line of tankless water heaters is the RTE-08 Electric. Highlights of this model include stainless steel construction to minimize heat loss and digital temperature settings. Its small size makes it convenient to install in cramped quarters, and in addition to traditional homes it can also be utilized to supply an endless source of hot water to offices, laboratories, hotels, and even boats.

Read on to find out what has made thisRheem tankless water heaterso popular!

Key Features

  • It has a temperature control unit that is easy to access.
  • LED lights indicate whether the RTE 9 is in active or standby mode.
  • The heat exchanger is crafted from a combination of brass and copper to ensure its durability.


  • The design of the Rheem RTE 9 includes self-modulating technology, which enables the unit to detect the temperature of the incoming water ahead of time and self-adjust its energy output accordingly.
  • Its small size minimizes the amount of space it requires for installation. Because it is an electric model, it does not have the same venting requirements as a gas model does.
  • It uses a standard ½” water connection. There’s no need to buy additional or specialty parts.


  • With a flow rate of only 3 gallons per minute (gpm), the Rheem RTE 9 will not be able to meet the hot water demands of most households.

Product Review

The Rheem RTE 9 has a maximum flow rate of 3 gpm, and it delivers a max wattage of 9,000. Because this unit is powered by electricity, it operates via a system of heat exchangers and internal sensors ““ as opposed to lighting an actual flame. This is ideal for homeowners who do not want to revamp their home’s current ventilation system.

The RTE 9 is a point of use model ““ meaning that it needs to be installed close to the faucets it will be servicing. With its relatively small flow rate, the RTE 9 can capably service one or two fixtures at a time. Large families or homeowners with bigger homes will either need invest in a more powerful tankless water heater or consider purchasing multiples of the RTE 9. This tankless heater can be connected with other Rheem tankless heaters to work simultaneously.

The RTE 9 Electric can comfortably offer water as hot as 102 degrees Fahrenheit. This temperature is more than sufficient to kill germs and bacteria, but individuals who prefer hotter showers may need to look elsewhere. Of course, this unit’s flow rate will be affected by your desired hot water temperature. The higher the desired temp is, the slower the flow rate will be. However, the good news is that Rheem electric tankless heaters have one of the smallest flow delays on the market today. In most instances, users will have the hot water they desire in 30 seconds or less.

Rheem offers a one year warranty on parts for this model and a ten year warranty for the heat exchanger. By and large, these warranties are on par with what is standard for the industry. As with most manufacturers, the RTE 9 must be installed by a professional, licensed technician in order for Rheem to honor its warranties. If you install it yourself, these warranties will be voided.

The brave homeowners who have installed this model themselves report that the process is fairly simple and straightforward ““ with a few caveats. Primarily, the cost of installation is going to depend on what type of pre-existing wiring you have in your home. This Rheem model requires, at a minimum, a 40 amp circuit and a 240 volt circuit breaker, in addition to 8 gauge wire. It should be installed indoors where it will be protected from inclement weather and dramatic changes in temperature.

Thank You For Reading

Overall, reviews for the Rheem RTE 9 have been mixed. Almost all reviewers agree that the unit is well-built and durable; however, for many, the model simply was not powerful enough to meet their hot water demands. Although it has an affordable price tag, most reviewers believe that it simply does not offer enough savings to justify its purchase price plus the cost of installation.

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