An energy measurement system for a lighting system, the lighting system comprising: - multiple lighting units arranged in multiple lighting zones (112, 114, 116; 430), - multiple sensors (111, 113, 115) associated with the lighting zones, and - an energy measurement device, the lighting system being arranged to switch on a lighting zone depending on at least a sensor associated with the lighting zone, the energy measurement system comprising: - a first receiver arranged for receiving sensor data from the multiple sensors (111, 113, 115), the sensor data indicating states of the multiple sensors at different times, - a second receiver arranged for receiving energy use data from the energy measurement device, the energy use data indicating an aggregated energy use of the multiple lighting zones at different times, and - a processor circuit arranged for - obtaining multiple pairs of a set of sensor identities and a corresponding energy use increase, said obtaining comprising: - determining from the sensor data a switching event during which one or more sensors of the multiple sensors changed state indicating switching on one or more associated lighting zones, and determining an identity of the one or more sensors which changed state, - determining an energy use increase associated with the switching event from the energy use data as the difference between an energy use after the switching event and an energy use on or before the switching event; and - obtaining power-on energy uses of the multiple lighting zones associated with the multiple sensors from the multiple pairs by relating the energy use increase with a corresponding power-on energy use of the lighting zones associated with the one or more sensor identities in the sets of sensor identities. - multiple lighting units arranged in multiple lighting zones (112, 114, 116; 430), - multiple sensors (111, 113, 115) associated with the lighting zones, and - an energy measurement device, - a first receiver arranged for receiving sensor data from the multiple sensors (111, 113, 115), the sensor data indicating states of the multiple sensors at different times, - a second receiver arranged for receiving energy use data from the energy measurement device, the energy use data indicating an aggregated energy use of the multiple lighting zones at different times, and - a processor circuit arranged for - obtaining multiple pairs of a set of sensor identities and a corresponding energy use increase, said obtaining comprising: - determining from the sensor data a switching event during which one or more sensors of the multiple sensors changed state indicating switching on one or more associated lighting zones, and determining an identity of the one or more sensors which changed state, - determining an energy use increase associated with the switching event from the energy use data as the difference between an energy use after the switching event and an energy use on or before the switching event; and - obtaining power-on energy uses of the multiple lighting zones associated with the multiple sensors from the multiple pairs by relating the energy use increase with a corresponding power-on energy use of the lighting zones associated with the one or more sensor identities in the sets of sensor identities.