Rheem Performance RTEX-11 11kW Electric Tankless Water Heater

The Rheem Performance RTEX-11 11kW Electric Tankless Water Heater is the small-whole-house electric tankless — 11kW for 2-person warm-climate whole-house or single-bathroom cold-climate service. 5-year heat exchanger warranty, digital thermostat.

Headline specifications

• Model: RTEX-11
• Power: 11kW at 240V
• Max flow rate: ~2.7 GPM at 35°F rise; ~3.5 GPM at 50°F rise
• Min activation flow: 0.3 GPM
• Temperature range: 80°F – 140°F
• Warranty: 5-year heat exchanger, 1-year parts
• Dimensions: 11" H × 8" W × 4" D
• Circuit: 2× 30-amp 240V (or 1× 50-amp depending on installation)

Who this model is for

2-person warm-climate whole-house installs, single-bathroom cold-climate service, small ADUs or cottages in moderate climates, vacation cabins or guest houses in 4-season locations with low daily use. 11kW handles concurrent shower + sink at warm inlets; in cold climates, it's single-fixture-at-a-time only.

For larger households or cold-climate concurrent demand, step up to RTEX-18. For lower demand or budget-tight installs, drop to RTEX-08.

Where it beats the alternatives

Vs RTEX-08: RTEX-11 adds 35% capacity for ~$40 more. The right step-up if your application demands concurrent shower + sink at any inlet temperature.

Vs RTEX-18: RTEX-11 saves ~$100 but caps lower. For genuinely whole-house cold-climate, RTEX-18 minimum.

Vs EcoSmart ECO 27: different scale — EcoSmart 27 is for full cold-climate whole-house. RTEX-11 is a step below that capacity tier.

Where it falls short

2.7 GPM at cold inlet limits whole-house in 4-season climates. For Northern states or mountain installs, this is single-bathroom service in winter.

Requires either 2× 30-amp circuits or 1× 50-amp — verify panel capacity.

1-year parts warranty.

No WiFi.

Install considerations

Electrical: 2× 30-amp 240V or 1× 50-amp 240V dedicated. 3/4" NPT plumbing recommended. Wall-mount.

Install cost: $500–$1,100 depending on electrical work and panel capacity.

Maintenance

• Annual descaling in hard-water regions
• Inlet filter clean annually
• Element check at year 4

Bottom line

The Rheem Performance RTEX-11 is the 2-person warm-climate whole-house electric tankless — 11kW, 2.7 GPM at cold inlet, 5-year heat exchanger warranty. For cold-climate or higher demand, step up to RTEX-18. For single-fixture or budget installs, drop to RTEX-08.