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 can reach as low as 37 Degree F. The ECO 27 is capable of heating nearly 3 GPM at this temperature. The ECO 27 is the largest electric tankless water heater available with self-modulating technology. These models are well suited for homes in the Northern U.S. and Canada and in the southern U.S. that have large Roman-style or Jacuzzi tubs and that have generally more demanding water usage needs.