The main aim of the article is to investigate the design and substantiates the principle of operation of a two-circuit electrode water heater, adapted for simultaneous connection of two heat-using installations when heating process water for hot water supply and heating systems. Justification is given for the hydraulic method of power control based on changes in the level of boiler water in the interelectrode space under the influence of thermal- and hydrodynamic processes. In this case, automatic regulation (self-regulation) of the electric power of the water heater is provided in accordance with the dynamics of changes in the thermal load of heat-using installations without the use of special regulating devices and automation tools. The possibility of step-by-step manual regulation of the heat power transmitted by the heat exchanger to the process water is shown. The results of experimental studies of the operation of a two-circuit electrode water heater in various modes are presented.