Rheem RTEX Electric Water Heaters Review and Buying Tips

What to expect from Rheem RTEX models, small electric and tankless water heaters from the Professional Classic series, designed for on-demand water heating, and delivering hot water in endless supply, in both point-of-use and whole-house applications.

Why Rheem electric tankless water heater is a good idea for your home

What makes Rheem RTEX water heaters different from other electric models of this manufacturer is the compact tankless size, efficient operation, delivering hot water fast, and with accurate temperature control.

Due to its small and lightweight design, Rheem RTEX models can fit almost anywhere, and the best is close to the point-of-use; under the sink, in the kitchen or bathroom, or small offices, providing hot water almost instantaneously.

Point-of-use models work the best for the isolated sinks where the central heating system requires long pipe runs.

Rheem electric tankless models are safe, reliable, and powerful. They deliver hot water non-stop because they heat on demand using one or more heating elements, modulating power, and accurate temperature control. There is no storage tank, stale hot water, and standby heat loss. With tankless heating, hot water is always fresh because cold water is heated only when it is needed - when the tap is open.

Models with high power usually require an upgraded electric panel.

Electric models do not require venting, as gas water heaters, also gas connections, gas valves, gas burners, and noisy electric blowers.

An overview of Rheem RTEX tankless electric water heaters

Rheem Performance 24 kw Self-Modulating 4.6 GPM Electric Tankless Water Heater (sold on homedepot.com)

Rheem tankless electric water heaters from the RTEX series are designed as indoor point-of-use (POU) models and recommended for one fixture, and whole-home models recommended for two or more fixtures.

POU models are available in 5 sizes, delivering from 3.5 kW to 13 kW 0 of power, operating from 120 to 240V, and from 29 to 54 Amps. Whole-house models are available in 4 sizes with power ranging from 18 to 36 kW, operating on 240V, and 75 to 150 Amps.

Rheem RTEX water heaters, with their stylish appearance, are truly modern electric appliances that incorporate high-quality immersion heating elements, made of corrosion-resistant copper and brass termination for durable operation.

Since the heating elements have threaded ends, they provide an easy replacement and service.

Rheem RTEX-04 and RTEX-06 models are equipped with only one heating element, where RTEX-04 operates on 120 V only.

Models RTEX-08, RTEX-11, RTEX-13, and RTEX-18 have two heating elements where the last model comes with self-modulation, allowing power adjustment depending on the hot water demand.

Water heaters RTEX-24 and RTEX-27 are also advanced as the RTEX-18 with the modulation, but these have three heating elements. In comparison, the RTEX-36 model has four heating elements, providing even more hot water for demanding homes.

All units, except RTEX-04 and RTEX-06, have a digital thermostatic control that allows precise temperature control from 80 to 140 F and in only 1 F increments. The outlet temperature can be seen on the unit's frontally located digital LED display, either in Celsius (C) or Fahrenheit (F).


Model/Specs kW AMPS Wire
Size (CU)
Max. Flow
RTEX-04 3.5 29 10 1.5
RTEX-06 5.5 25 10 2.0
RTEX-08 5.8-8.0 33 8 4.8
RTEX-11 8.2-11 46 6 4.8
RTEX-13 10.1-13 54 6 4.8
RTEX-18 13.3-18 75 8 7
RTEX-24 17.5-24 100 8 7
RTEX-27 20-27 112 8 7
RTEX-36 26.6-36 150 8 8

Similar models: Stiebel Eltron Tempra and Titan

Buying one of the Rheem RTEX models is a no-brainer; they provide an easy installation with the provided electric cord and side or bottom water connections, maintenance, and reliable heating for years to come. The system doesn't have many high-tech elements as its gas counterpart, so it doesn't break easily or require complicated maintenance, plus it is cheaper.

At the same time, it provides an endless supply of hot water, fast and with a consistent outlet temperature, where the energy efficiency is close to 100%. Unfortunately, none of the tankless electric models, no matter the manufacturer, is Energy Star compliant.

However, homeowners can still take advantage of savings of up to 50% on water heating costs, no matter where it is used: showers, baths, kitchens, at home, RVs, cabins, garages, barns, even commercial use.

All Rheem RTEX electric tankless water heaters come with a 5-year warranty on the heating elements and one year for other components.


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