The present invention relates to an integrated plant which comprises a plant for the electrothermic production of hydrogen cyanide and a plant for electricity generation, the plant for the electrothermic production of hydrogen cyanide being connected to the plant for electricity generation via a conduit and electricity being generated in the plant for electricity generation from a product gas obtained in the plant for the electrothermic production of hydrogen cyanide. This integrated plant affords flexible use of electricity by a method in which, at times of a high electricity supply, the plant for the electrothermic production of hydrogen cyanide is operated and at least some of the hydrogen and/or gaseous hydrocarbons obtained in addition to hydrogen cyanide is stored and, at times of a low electricity supply, stored hydrogen and/or gaseous hydrocarbons are fed to the plant for electricity generation.