Abstract: In various aspects, the present application describes a tankless liquid heater receiving liquid at an inlet and providing heated liquid at an outlet. The tankless liquid heater may include a heating element for heating liquid received from the inlet. A flow sensor indicates the flow rate of the liquid received by the heating element. The heater includes a temperature sensor measuring the temperature of liquid exiting the heating element. A controller of the heater regulates the amount of electrical current energizing the heating element responsive to the flow sensor and the temperature sensor, energizes the heating element when the flow rate of the liquid exceeds a predefined value and prevents energizing the heating element when the heated liquid exceeds a predefined temperature. The heater may also include a thermostatic mixing valve for mixing the heated liquid with liquid diverted from the inlet responsive to the temperature of the heated liquid.