Method for operating an electrical installation having a plurality of electrical loads (1,2,3,4) which are connected to a basic supply voltage and in the event of the basic supply voltage failing are connected to a backup voltage, in order to safeguard the supply to the electrical loads (1,2,3,4) for a duration of a backup phase, wherein the backup voltage is provided by means of an uninterruptible power supply unit, characterised in that - the power supply unit is connected to the plurality of electrical loads (1,2,3,4) via a field bus to exchange data, - the plurality of electrical loads (1,2,3,4) are each provided with a software module (11,12,13,14,15) which is integrated into the communication via the field bus, - the software module of at least one load is appointed as a master and the software modules (11,12,13,14) of the other loads (2,3,4) as slaves in the context of master-slave communication, - the master in the power supply unit is entered as a communication partner for performance of a regulated shutdown procedure of the electrical loads (1,2,3,4), - in the event of a failure of the basic supply voltage the power supply unit notifies the master of said failure via the field bus and as a result the regulated shutdown procedure is launched, - the shutdown procedure takes place in configurable synchronisation stages (S1,S2,S3,S4,S5...), - for each of the synchronisation stages (S1,S2,S3,S4,S5...) the relevant software module (11,12,13,14) for each load (1,2,3,4) stores whether the load should maintain or change its energy state and, if several energy state changes are possible and provided for, to which energy state it should change, - the master signals each of the synchronisation stages (S1,S2,S3,S4,S5...) consecutively to the loads (1,2,3,4), - the energy state changes of the loads (1,2,3,4) stored in the software modules (11,12,13,14) are executed for the respective synchronisation stage (S1,S2,S3,S4, S5...) and - after execution the corresponding software module (11,12,13,14) reports this to the master. - the power supply unit is connected to the plurality of electrical loads (1,2,3,4) via a field bus to exchange data, - the plurality of electrical loads (1,2,3,4) are each provided with a software module (11,12,13,14,15) which is integrated into the communication via the field bus, - the software module of at least one load is appointed as a master and the software modules (11,12,13,14) of the other loads (2,3,4) as slaves in the context of master-slave communication, - the master in the power supply unit is entered as a communication partner for performance of a regulated shutdown procedure of the electrical loads (1,2,3,4), - in the event of a failure of the basic supply voltage the power supply unit notifies the master of said failure via the field bus and as a result the regulated shutdown procedure is launched, - the shutdown procedure takes place in configurable synchronisation stages (S1,S2,S3,S4,S5...), - for each of the synchronisation stages (S1,S2,S3,S4,S5...) the relevant software module (11,12,13,14) for each load (1,2,3,4) stores whether the load should maintain or change its energy state and, if several energy state changes are possible and provided for, to which energy state it should change, - the master signals each of the synchronisation stages (S1,S2,S3,S4,S5...) consecutively to the loads (1,2,3,4), - the energy state changes of the loads (1,2,3,4) stored in the software modules (11,12,13,14) are executed for the respective synchronisation stage (S1,S2,S3,S4, S5...) and - after execution the corresponding software module (11,12,13,14) reports this to the master.