A lighting system controller for a lighting management system comprising the lighting system controller, a lighting system and a grid controller, the lighting system controller provided for controlling operation of the lighting system that comprises a plurality of luminaires for illuminating respective locations of a space and a plurality of occupancy sensors arranged in said space, wherein respective light output of each of the plurality of luminaires is controlled at least in part in accordance with occupancy indications obtained from an occupancy sensor associated therewith, the lighting system controller being arranged to: estimate a minimum allowable power consumption of the lighting system and a maximum allowable power consumption of the lighting system for a predefined time period; estimate a baseline power consumption of the lighting system at the predefined time period, wherein the baseline power consumption comprises one of a current power consumption of the lighting system or a predicted power consumption of the lighting system for a future time period; determine respective capacities for reducing or increasing the power consumption of the lighting system at the predefined time period based on the estimated baseline power consumption in dependence of the estimated minimum allowable power consumption and the estimated maximum allowable power consumption; provide information that defines the determined respective capacities for reducing or increasing the power consumption of the lighting system at the predefined time period to the grid controller arranged for facilitating a balance between electricity production to and electricity consumption from an electrical grid that serves to supply operating power to the lighting system; and control, in response to a request from the grid controller to one of reduce or increase the power consumption of the lighting system, one or more luminaires (122-k) of the plurality of luminaires to one of reduce or increase their respective light outputs in accordance with said request characterized in that the lighting system controller is arranged to estimate the minimum allowable power consumption of the lighting system based on respective predefined minimum allowable light intensity levels assigned to said plurality of luminaires and estimate the maximum allowable power consumption of the lighting system based on respective predefined maximum allowable light intensity levels assigned to said plurality of luminaires, wherein the minimum and maximum allowable power consumptions are estimated for the predefined time period in dependence of the occupancy indications obtained for said plurality of luminaires from the respective one of said plurality of occupancy sensors associated with respective one of said plurality of luminaires. estimate a minimum allowable power consumption of the lighting system and a maximum allowable power consumption of the lighting system for a predefined time period; estimate a baseline power consumption of the lighting system at the predefined time period, wherein the baseline power consumption comprises one of a current power consumption of the lighting system or a predicted power consumption of the lighting system for a future time period; determine respective capacities for reducing or increasing the power consumption of the lighting system at the predefined time period based on the estimated baseline power consumption in dependence of the estimated minimum allowable power consumption and the estimated maximum allowable power consumption; provide information that defines the determined respective capacities for reducing or increasing the power consumption of the lighting system at the predefined time period to the grid controller arranged for facilitating a balance between electricity production to and electricity consumption from an electrical grid that serves to supply operating power to the lighting system; and control, in response to a request from the grid controller to one of reduce or increase the power consumption of the lighting system, one or more luminaires (122-k) of the plurality of luminaires to one of reduce or increase their respective light outputs in accordance with said request characterized in that the lighting system controller is arranged to estimate the minimum allowable power consumption of the lighting system based on respective predefined minimum allowable light intensity levels assigned to said plurality of luminaires and estimate the maximum allowable power consumption of the lighting system based on respective predefined maximum allowable light intensity levels assigned to said plurality of luminaires, wherein the minimum and maximum allowable power consumptions are estimated for the predefined time period in dependence of the occupancy indications obtained for said plurality of luminaires from the respective one of said plurality of occupancy sensors associated with respective one of said plurality of luminaires.