Check the listing for details. EcoSmart 18 W Tankless Electric Water Heater ECO 18. Color: White, Condition: New. Listed at 461.99 USD. EcoSmart Electric tankless water heaters, also called Instantaneous on demand water heaters, provide endless hot water on demand and only as needed. Self-modulating flow sensor technology regulates the amount of energy required to heat the water needed. This smart technology electric tankless water heater is configured for climates where incoming water temperature is 62 degree Fahrenheit and above. The ECO 18 is capable of heating over 2.5 GPM, which is the equivalent of one shower head (with a 1.5 GPM flow) and one sink with a low inlet water temperature of 62 degree Fahrenheit. Two showers can be run simultaneously when incoming water temperature is above 70 degree Fahrenheit in warmer climates such as South Texas, South Florida, New Mexico, Arizona and South California.