description Rheem RTEX-18 Overview
The Rheem RTEX-18 is an 18-kilowatt electric tankless water heater designed to heat water on demand without a storage tank. It provides external digital thermostatic control and requires an electrical installation sized for its high power draw, so suitability depends on service capacity, wiring, flow rate, and incoming water temperature. It is intended for residential applications where its specified output can meet the required hot-water demand.
help Rheem RTEX-18 FAQ
Can the Rheem RTEX-18 supply a whole house or only one shower?
Rheem rates the 18 kW RTEX-18 for multiple point-of-use applications, but actual capacity depends heavily on incoming-water temperature and simultaneous flow. A standard shower uses around 2 GPM, while Rheem lists a maximum flow figure of up to 4.4 GPM under favorable conditions.
What electrical service does an RTEX-18 installation require?
The RTEX-18 is a high-draw 240-volt appliance and normally uses two dedicated 40-amp double-pole circuits with appropriately sized wiring. An electrician should verify panel capacity before purchase because replacing a tank heater does not automatically mean the existing circuit is sufficient.
What temperature range can be selected on the RTEX-18?
Its external digital control adjusts the set point in 1-degree increments from 80°F to 140°F, equivalent to roughly 26°C to 60°C. The delivered temperature can still fall below the setting if demand exceeds the heater's available power.
Does the Rheem RTEX-18 need venting or a storage tank?
No. It is an electric tankless unit, so it heats water on demand without a flue or stored reservoir, unlike Rheem's conventional Professional Classic tank models.
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