EcoSmart ECO 36
#1 in ElectricFull review
For a large home with 300 A service that wants all electric hot water. The lifetime warranty and low price per kilowatt make it a strong value if a pro installs it.
Amazon $699$699
The EcoSmart ECO 36 is the better tankless water heater overall, rated 4.3 to 3.0. The EcoSmart ECO 36 leads on warranty, heating power and value. The Rheem RTEX-24 costs $150 less ($549 vs $699).
Rheem RTEX-24
#12 in ElectricFull review
A mainstream whole home heater for a two bathroom house in a warm climate. The Stiebel Tempra 24 Trend costs about the same with a longer warranty.
Amazon $549$549
Prices 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.
Which should you buy?
- Choose the EcoSmart ECO 36 for warranty (limited lifetime heat exchanger warranty vs 5-year heat exchanger warranty), heating power (36 kW vs 24 kW) and value ($19.42 per kW ($699, 36 kW) vs $22.88 per kW ($549, 24 kW)).
Scores side by side
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 | EcoSmart ECO 36 | Rheem RTEX-24 |
|---|---|---|
| Overall rating | 4.3/5 | 3.0/5 |
| Value 35% | 64 $19.42 per kW ($699, 36 kW) | 51 $22.88 per kW ($549, 24 kW) |
| Heating power 25% | 100 36 kW | 52 24 kW |
| Efficiency 15% | 50 0.94 UEF | 38 0.93 UEF |
| Warranty 25% | 100 limited lifetime heat exchanger warranty | 29 5-year heat exchanger warranty |
Specifications
| EcoSmart ECO 36 | Rheem RTEX-24 | |
|---|---|---|
| Heating | ||
| Fuel | Electric | Electric |
| Electric power | 36 kW | 24 kW |
| Max flow | 8.8 GPM | 5.9 GPM |
| UEF | 0.94 | 0.93 |
| Installation | ||
| Voltage | 240 V | 240 V |
| Breakers | 160 A total | 120 A total |
| Weight | 18.4 lb | - |
| Features | ||
| Built-in recirculation | No | No |
| Wi-Fi | No | No |
| Heat exchanger warranty | Limited lifetime | 5 years |
| Parts warranty | - | 1 year |