Rheem RTEX-13 13kW Electric Tankless Water Heater

The Rheem RTEX-13 is the smaller sibling of the popular RTEX-18, designed for 1-bathroom homes in moderate climates. At 13 kW pulling 54 amps at 240V on a single feed (two 30-amp double-pole breakers), it fits comfortably in most 100A panels and easily in 200A panels. Capacity: about 2.1 GPM at a 40°F rise (southern winter) or 1.5 GPM at a 60°F rise (northern winter). One shower at a time anywhere in the country.

The product targets the largest single demographic in the electric-tankless market: 1-person and 1-bath homes in the Sun Belt replacing an aging 30–40 gallon electric tank. For that buyer, the RTEX-13 frees up the floor space the tank occupied, eliminates the standby losses of a heated reservoir, and produces continuous hot water at the single bathroom for under $800 installed.

Lifetime warranty on the heat exchanger, 5-year warranty on electronics. Self-modulating power management in 0.5 kW increments. Copper heat exchanger — descale annually in hard water. Service through Rheem's national plumber network, parts at any Rheem dealer or Home Depot pro counter.

Not the right fit for: 2-bath homes (any climate), 1-bath homes in cold climates, or households with overlapping handwash + shower use even in mild climates. The RTEX-18 covers those scenarios at a modest step-up in install cost.