The Stiebel Eltron Tempra 15 Plus is the better tankless water heater overall, rated 2.6 to 2.4. The Stiebel Eltron Tempra 15 Plus leads on efficiency, warranty and heating power. The Rheem RTEX-11 wins on value. The Rheem RTEX-11 costs $350.01 less ($268.99 vs $619).
For a small home or cabin on a 100 A service in a warm climate where a steady shower temperature matters more than flow. Homes with more service get more for the money from a Trend model.
Amazon $619For a single shower or a pair of sinks in a warm climate. The EcoSmart ECO 11 costs less and carries a lifetime warranty.
Amazon $268.99Prices were last checked October 31, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Each factor is scored 0-100 against the same fixed reference points for every electric tankless water heater; a clear win is highlighted. How we rank explains each one.
| Factor weight | Stiebel Eltron Tempra 15 Plus | Rheem RTEX-11 |
|---|---|---|
| Overall rating | 2.6/5 | 2.4/5 |
| Value 35% | 3 $42.99 per kW ($619, 14.4 kW) | 46 $24.45 per kW ($268.99, 11 kW) |
| Heating power 25% | 14 14.4 kW | 0 11 kW |
| Efficiency 15% | 75 0.96 UEF | 25 0.92 UEF |
| Warranty 25% | 57 7-year heat exchanger warranty | 29 5-year heat exchanger warranty |
| Stiebel Eltron Tempra 15 Plus | Rheem RTEX-11 | |
|---|---|---|
| Heating | ||
| Fuel | Electric | Electric |
| Electric power | 14.4 kW | 11 kW |
| Max flow | 3 GPM | 2.7 GPM |
| UEF | 0.96 | 0.92 |
| Installation | ||
| Voltage | 240 V | 240 V |
| Breakers | 60 A total | 50 A total |
| Weight | 16.1 lb | 6.5 lb |
| Features | ||
| Built-in recirculation | No | No |
| Wi-Fi | No | No |
| Heat exchanger warranty | 7 years | 5 years |
| Parts warranty | 3 years | 1 year |
