The invention relates to a method and a device for supporting the frequency in an electricity network (5) during a sudden modification of the network load and/or generating power. According to the invention, modifications of the network load and/or generating power, which cause the network frequency to deviate from a predefined value, are compensated by a modification of an additional load (6). Said additional load (6) is preferably configured by a large number of hydrogen-producing electrolysis units (7), which can be activated or deactivated for the successive modification of the additional load.