Abstract: In a method and an apparatus for regulating the power which is supplied to a heating element (2) in a water heater (1), preferably a reservoir water heater containing water which is to be heated to a certain temperature, the power which is supplied to the heating element for heating the water, is regulated not only in dependence on the temperature of the water (15), but also in dependence on the temperature of the heating element (2, 4), so that the temperature of the element is kept below a predetermined critical value. The temperature of the heating element is measured directly and/or indirectly, and when the temperature of the element is below the critical value and the temperature of the water in the water heater is below the rated value, maximum power can be supplied to the heating element.