Rheem Professional Classic® 36 kW Electric Tankless Water Heater

Overview & Key Features

Performance & Efficiency

• On-demand, continuous hot water—provides endless supply without a storage tank. PlumbersCrib.comMyRheem Files

• Highly efficient—delivers up to 99.8% energy efficiency, with a UEF (Uniform Energy Factor) around 0.94. PlumbersCrib.comRheem USAMyRheem Files

Design & Controls

• Digital thermostatic control—adjust temperatures in 1 °F increments (range: 80 °F–140 °F / 26 °C–60 °C). PlumbersCrib.comMyRheem Files

• Compact, space-saving design—up to 93% smaller than conventional electric tank heaters. MyRheem Files

• No venting required—streamlines installation compared to gas models. MyRheem Files

Build & Durability

• Constructed with copper immersion heating elements and a multi-chamber design for rapid heat-up and consistent temperature control. MyRheem Files

• Features a copper heat exchanger for efficient thermal transfer and enhanced corrosion resistance. MyRheem Files

• Durable exterior—powder-coated shell with a galvanized steel backplate and brass NPT inlet/outlet fittings ensure long-term reliability. MyRheem Files

Technical Specifications

Use Cases & Applications

• Whole-home usage—capable of handling multiple fixtures and demands simultaneously, such as showers, sinks, and appliances. PlumbersCrib.com

• Common applications include:

  • Standard shower heads (~2 GPM)

  • Bath tubs (~4 GPM)

  • Kitchen sinks (~1–2 GPM)

  • Dishwashers (~1–2 GPM)

  • Washing machines (~1–1.5 GPM) PlumbersCrib.com

Highlights & Advantages

• Ultra-efficient electric heating—virtually zero wasted energy when not in use. MyRheem Files

• Compact and easy to install—no need for venting, saving space and simplification during installation. MyRheem Files

• Precise temperature control—ideal for maintaining consistent comfort via digital settings. PlumbersCrib.comMyRheem Files

• Robust build quality—durable heat exchanger and fittings designed for long life. MyRheem Files

Considerations

• High electrical demand—requires a substantial electrical capacity, including 150 A and multiple breakers.

• Installation complexity—upgrade to your electrical panel may be needed if the home isn’t wired for such high load.

• Flow dependency—minimum activation flow is low, but output depends on inlet temperature. Cold locations may reduce max GPM.

Summary

The Rheem Professional Classic® RTEX-36 (36 kW) is a powerful, efficient, and compact electric tankless water heater—perfect for whole-home applications where venting isn’t desired or feasible. Expect excellent energy performance, precise controls, and space-saving convenience, provided your electrical infrastructure can support it.