An instant water heater utilizing positive temperature coefficient plastic electrically conductive material structures for electrodes. The heating of the water is not generated by the electrodes, but instead by the resistance of the water to the electrical current flowing between them. The material of the electrodes undergoes a phase change at certain temperatures when whereby it converts from electrically conductive to electrically non-conductive at a predetermined temperature. The output temperature of the water is determined by a combination of the area of the electrodes that confront one another, the water's conductivity, the flow rate of the water and the current limiting capability of the conductive electrode materials positive temperature coefficient, which reduces or stops the heating of the water when the intended water temperature is achieved.