Rheem RTEX-04 Review

Read time: 5 minutes Last Updated: 09/18/2019

Rheem RTEX-04

  • 5-year warranty covers most of average lifespan
  • Compact form factor allows for flexible installation options
  • Solid 80°F to 140°F temperature range exceeds size class averages
  • Affordably priced for novice and first-time tankless water heater users
  • May struggle to reach max temperature with cold groundwater
  • Return window is too small
Dimensions & Capacity:
3 x 11 x 6 inches
Fuel Type:
Flow Rate & Water Pressure:
2 GPM standard, 6 GPM peak (when part of a larger system)
Heating Capacity:
80°F to 140°F.
Energy Efficiency Ratings & Certifications:
99.8%, Water Quality Association and ETL
Price and Warranty:
Under $200, 5-year warranty
Display Type:
Material Composition:
Stainless Steel
Our Review

Every aspect of the Rheem RTEX-04 is geared towards providing instantaneous hot water to your home’s numerous spigots, faucets, and showers. Between its core specifications and its special features, the Rheem RTEX-04 provides a strong standard of performance that won’t degrade after years of use. 

One special feature that deserves some extra attention on the Rheem RTEX-04 is its overall flexibility and ease of installation. Though this is partially the result of its compact form factor and simplified port set up, most novice DIYers will be able to mount this unit in even a cramped crawl space without worrying about losing access once the unit is operational. You may even choose to mount the Rheem RTEX-04 next to a larger tankless unit in order to create a convenient control hub for your whole home.

Read more about our how our ratings broke down for the RTEX-04 below or checkout how it compares to other electric water heaters.

Why Might I Want this Specific Tankless Water Heater?

Like a magician snapping their fingers, you can expect instant results from the Rheem RTEX-04 as soon as it is called upon to provide hot water. Not only is the Rheem RTEX-04 efficient in its operation, but it is also capable of providing a nearly 6 GPM flow rate when installed as part of a whole-home tankless water heater system. Depending on groundwater temperatures, the Rheem RTEX-04 can even output hot water up to 140 °F

Also, the Rheem RTEX-04 can be seen as the absolute best way to try out tankless water heating without needing to drop hundreds of dollars. The Rheem RTEX-04 costs just over $150, making it affordable on almost any DIY budget. For that price, you’ll still receive a unit with the user-friendly digital interface that has made Rheem tankless models popular among American homeowners.

Key Specifications and Features to Look for in a Tankless Water Heater

Dimensions & Capacity

While picking a tankless water heater, you’ll need to keep physical dimensions in mind to prevent an aggravating incongruity with your desired installation location. By way of an example, the Rheem RTEX-04’s dimensions measure out to 3 x 11 x 6 inches, making it an ideal candidate for installation in a small cabinet or beside other components of your home’s climate control system. This small size has no impact on the Rheem RTEX-04’s capacity because it (like all tankless units) lacks any need to internally store water.

Fuel Type

Fuel sources for tankless units will vary between electric, natural gas, and propane. Each type provides its own distinct benefits in terms of operational price and extra installation requirements (such as venting). The Rheem RTEX-04 is an electric-powered unit, making it unnecessary to spend extra to modify your home’s infrastructure at the time of installation.

Flow Rate & Water Pressure

In context, a tankless unit’s flow rate describes how much groundwater it can take in, heat, and output over a period of time (often expressed in gallons per minute or GPM). This movement rate then impacts a water delivery system’s overall water pressure, which is essential for satisfactory and sanitary use. The Rheem RTEX-04’s 2 GPM standard rate is plenty strong enough to supply a single shower or sink in a low-demand setup.

Heating Capacity

A unit’s heating capacity (expressed as a temperature range) describes the temperatures to which the unit is capable of heating groundwater. This metric is important to consider based upon your intended cooking and sanitary needs. In completing its primary function, the Rheem RTEX-04 is able to heat groundwater as cold as 48°F to anywhere between 80°F and 140°F.

Energy Efficiency Ratings & Certifications

Energy efficiency is a major sell for most tankless units and is often expressed (based upon the manufacturer’s testing) as a percentage out of 100. These efficiency ratings sometimes lead to a given unit gaining special regulatory certifications for their quality. The Rheem RTEX-04 99.8% energy efficiency rating is remarkable in its own right, though it has only gained certifications from the Water Quality Association and ETL.

Price and Warranty

Finding the best deal on a new tankless unit is always important when renovating your in-home hot water production and delivery system on a budget. Prices often take into account added-value factors such as the 5-year warranty on the Rheem RTEX-04. Even so, that model only costs a little bit over $150.

Display Type

You’ll need to interact with your tankless unit on a regular basis, so it is important to find a model that is as user-friendly as the Rheem RTEX-04. That model makes use of a digital interface that is similar to the style seen on larger Rheem models. As a result, this model is far easier to use than any other analog interface tankless unit.

Different Uses for a Tankless Water Heater

Decentralized In-Home Water Heating

Many folks seek out a tankless unit like the Rheem RTEX-04 in order to fully or partially decentralize their in-home hot water production and distribution system. Completing such a task brings with it some productive benefits, including enhancing efficiency and a lower reliance on anyone appliance for the entire home’s hot water production. Also, a decentralized system is far easier to modify and maintain without the help of a plumber.

Cutting Water and Electric Bills

When upgrading to a tankless unit like the Rheem RTEX-04, you can expect to save yourself a pretty penny as your next few utility bills arrive. That is because a tankless unit’s heating chambers more efficiently convert the chosen fuel source into heat, at rates of 90% or higher. Also, a lack of internal holding tank means that a tankless unit categorically uses only the water required to meet a user’s demand.