Rheem Performance RTEX-08 8kW Electric Tankless Water Heater

The Rheem Performance RTEX-08 8kW Electric Tankless Water Heater is the mid-ladder electric tankless — 8kW for low-demand point-of-use installs and single-bathroom warm-climate whole-house service. 5-year heat exchanger warranty, digital thermostat.

Headline specifications

• Model: RTEX-08
• Power: 8kW at 240V
• Max flow rate: ~2.0 GPM at 35°F rise; ~2.7 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: 1× 40-amp 240V

Who this model is for

Single-bathroom whole-house in warm climates (Florida, Texas, Arizona, Southern California where inlet water exceeds 65°F most of the year), high-demand point-of-use (shower + sink concurrent at low-flow), small ADUs / accessory dwellings, vacation cabins in warm regions.

Wrong product for whole-house in cold-climate regions where inlet drops to 35°F in winter — at that inlet, 8kW caps at 2.0 GPM which is below typical concurrent demand. For cold-climate whole-house electric tankless, step up to RTEX-11 or higher.

Where it beats the alternatives

Vs RTEX-06T: RTEX-08 adds 33% more capacity for ~$40 more. The point-of-use vs whole-house distinction in Rheem's lineup is blurry — RTEX-06T is marketed as PoU, RTEX-08 as whole-house, but the difference is mostly the model badging and target market.

Vs RTEX-11: RTEX-08 saves ~$40 but caps lower. For cold-climate whole-house, RTEX-11 minimum.

Vs EcoSmart ECO 8: spec-near-equivalent. EcoSmart slightly cheaper; Rheem stronger retail availability.

Where it falls short

2.0 GPM at cold inlet — won't support concurrent shower + dishwasher in cold climates. Warm-climate whole-house only.

40-amp 240V circuit required. Older homes with 100-amp service may struggle.

1-year parts warranty.

No WiFi.

Install considerations

40-amp 240V dedicated circuit. 1/2" or 3/4" NPT plumbing. Wall-mount.

Install cost: $400–$900 depending on electrical work.

Maintenance

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

Bottom line

The Rheem Performance RTEX-08 is the warm-climate single-bathroom electric tankless — 8kW, 2.0 GPM at cold inlet, 5-year heat exchanger warranty. For cold-climate whole-house, step up to RTEX-11. For point-of-use single fixture, drop to RTEX-06T.