A method for producing electrical energy in a combined energy generation plant (100, 200) which comprises an air treatment unit (10) and a power station unit (20) is proposed. In a first operating mode, air (AIR) is liquefied to form an air liquefaction product (LAIR) and, in a second operating mode, an air liquefaction product (LAIR) is converted into a gaseous or supercritical state, in which said product is introduced into the power station unit (20) and is used for producing electrical energy. In a third operating mode, air (AIR) is condensed in the air treatment unit (10) and used in the power station unit (20) directly for producing electrical energy. It is envisaged that, in the first operating mode, the air (AIR) is cooled to several temperature levels (T1 - T5) by two liquid coolants and the air liquefaction product (LAIR) is correspondingly heated. In addition, in the first operating mode, the air (AIR) is condensed stepwise over several pressure levels (LP, MP, MP1, HP). In addition, in the second operating mode, the air liquefaction product (LAIR) is heated to a further pressure level (HP1) and introduced into the power station unit (20) at this pressure level in gaseous form. Finally, in the third operating mode, the air (AIR) is introduced into the power station unit (20) in separate batches and at different pressure levels (MP1, HP or HP1). A corresponding energy generation plant (100, 200) is likewise the subject matter of the invention.