EcoSmart ECOS 27
#7 in ElectricFull review
A low cost whole home heater for a two bathroom house in a warm climate. The short warranty is the tradeoff for the price.
Amazon $549$549
The EcoSmart ECOS 27 is the better tankless water heater overall, rated 3.3 to 2.9. The EcoSmart ECOS 27 leads on heating power and value. The EcoSmart ECOS 18 wins on efficiency. The EcoSmart ECOS 18 costs $100 less ($449 vs $549).
EcoSmart ECOS 18
#14 in ElectricFull review
For a small home or apartment in a warm climate that wants whole house hot water on two breakers. Amazon stock was low when checked.
Amazon $449$449
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 ECOS 27 for heating power (27 kW vs 18 kW) and value ($20.33 per kW ($549, 27 kW) vs $24.94 per kW ($449, 18 kW)).
- Choose the EcoSmart ECOS 18 for efficiency (0.96 UEF vs 0.94 UEF).
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 ECOS 27 | EcoSmart ECOS 18 |
|---|---|---|
| Overall rating | 3.3/5 | 2.9/5 |
| Value 35% | 60 $20.33 per kW ($549, 27 kW) | 45 $24.94 per kW ($449, 18 kW) |
| Heating power 25% | 64 27 kW | 28 18 kW |
| Efficiency 15% | 50 0.94 UEF | 75 0.96 UEF |
| Warranty 25% | 29 5-year heat exchanger warranty | 29 5-year heat exchanger warranty |
Specifications
| EcoSmart ECOS 27 | EcoSmart ECOS 18 | |
|---|---|---|
| Heating | ||
| Fuel | Electric | Electric |
| Electric power | 27 kW | 18 kW |
| Max flow | 6.6 GPM | 4.4 GPM |
| UEF | 0.94 | 0.96 |
| Installation | ||
| Voltage | 240 V | 240 V |
| Breakers | 120 A total | 80 A total |
| Weight | 10.9 lb | 9.3 lb |
| Features | ||
| Built-in recirculation | No | No |
| Wi-Fi | No | No |
| Heat exchanger warranty | 5 years | 5 years |
| Parts warranty | 1 year | 1 year |