In various aspects, the present invention provides an electric tankless liquid heater system capable of delivering liquid, such as, for example, water, with an acceptable increase in output liquid temperature upon a sudden and substantial decrease in liquid demand. In various aspects, the electric tankless liquid heater comprises an inlet manifold and a plurality of liquid heaters the inlets of which are connected in a parallel flow relationship by the inlet manifold, and the outlets of which are each connected to a separate outlet conduit, and which is configured to provide water to a plurality of automatic water fixtures with a less than about 2° F. (about 1.1° C.) increase in output water temperature upon about a one-and-a-half-fold or greater decrease in water demand that occurs in less than about 500 milliseconds as measured by the increase time of the inlet liquid pressure.