Rheem Performance RTEX-04T 4kW Electric Tankless Water Heater (Point of Use)

The Rheem Performance RTEX-04T 4kW Electric Tankless Water Heater is the smallest of Rheem's electric tankless ladder — a 4kW point-of-use unit for a single faucet or bar sink. 240V, digital temperature control, compact enough to mount under a sink. The right pick when you need on-demand hot water for one fixture and don't want a mini-tank's standby losses.

Headline specifications

• Model: RTEX-04T
• Type: Point-of-use electric tankless
• Power: 3.5kW (240V) / 4kW configurations
• Max flow rate: ~1.0 GPM at 35°F rise (lower at colder inlet)
• Min activation flow: 0.3 GPM
• Temperature range: 80°F – 140°F (digital control)
• Warranty: 5-year heat exchanger, 1-year parts
• Dimensions: 9" H × 7" W × 3.5" D (extremely compact)
• Circuit: 20-amp 240V

Who this model is for

Single-fixture point-of-use applications: remote bathroom sink 40+ ft from main heater, kitchen island sink, garage utility sink, basement wet bar, workshop hand-wash. The 4kW unit handles a single low-flow faucet at warm-climate inlet temperatures — not enough capacity for a shower or even a kitchen sink in cold inlet regions.

For higher flow at the same point-of-use class, step up to RTEX-06T or RTEX-08. For mini-tank alternative at same single-fixture scale, the Performance 6G Mini-Tank at 120V plug-in is simpler install with no GPM limit (just storage limit).

Where it beats the alternatives

Vs Performance 6G Mini-Tank: tankless has no standby losses (mini-tank reheats periodically even when not used). For low-frequency-use installations (vacation cabin, occasional-use bar sink), tankless saves on annual electricity. For high-frequency use, mini-tank's continuous availability wins.

Vs Eemax SP3512 point-of-use: spec-near-equivalent. Eemax has slightly larger US installer network in commercial/dental applications. Rheem wins on residential / Home Depot availability.

Vs RTEX-06T: RTEX-04T saves ~$40 but caps at lower flow. Step up if you need 1.5 GPM rather than 1.0.

Where it falls short

1.0 GPM at 35°F rise is the limit — in cold-climate winters (35°F inlet), output flow drops below what most modern low-flow faucets demand (1.2 GPM). Warm-climate installs (65°F inlet) get closer to 1.5 GPM effective.

20-amp 240V dedicated circuit required. Plug-in not available (unlike mini-tanks).

1-year parts warranty (vs 5-year heat exchanger).

Digital control is basic — no WiFi, no app integration.

Brand recognition in electric tankless is lower than EcoSmart and Stiebel; Rheem RTEX is a value play.

Install considerations

20-amp 240V dedicated circuit (verify panel capacity). 1/2" NPT cold inlet, 1/2" NPT hot outlet. Wall-mount, very compact form factor — fits in vanity cabinets.

Install cost: $250–$550 depending on whether electrical circuit needs to be run.

Maintenance

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

Bottom line

The Rheem Performance RTEX-04T is the smallest electric tankless — single-fixture point-of-use at warm-climate inlet temperatures. 5-year heat exchanger warranty. For higher flow, step up to RTEX-06T. For mini-tank alternative simpler install, see Performance 6G Mini-Tank.