In various embodiments, the invention provides a system for heating a liquid, such as, for example, water, comprising a plurality of liquid heaters, the inlets and outlets of which are respectively connected in a parallel flow relationship by respective manifolds, and configured to provide liquid having a temperature of greater than about 90 degrees Fahrenheit at a flow rate of greater than about 10 gallons per minute. In various embodiments, the present invention provides an electric tankless liquid heater system capable of delivering hot liquids, and in particular water, at even higher flow rates and or temperatures, including, but not limited to, flow rates greater than about: (1) 12 gpm; (2) 18 gpm; (3) 20 gpm; and (5) 20 gpm; and/or temperatures of greater than about: (1) 100.degree. F.; (2) 120.degree. F.; (3) 140.degree. F.; and (4) 180.degree. F.