This invention relates to a method of controlling the light output of a solar-powered lighting device. The lighting device comprises a light source, a battery connected to the light source, a solar-power generator including a charger connected to the battery, and a control unit for performing the light output control. The method comprises: —charging the battery while solar-power is generated; —acquiring local day-light data; —repeatedly: —acquiring, at predetermined time intervals, local weather forecast data covering a predetermined time period, and determining a lighting output profile for the predetermined time period; and —driving the lighting device according to the lighting output profile, wherein said determining a lighting output profile comprises: —predicting a lighting demand for the predetermined time period on basis of first environment light data, which first environment light data comprises the local day-light data; —predicting a battery capacity for the predetermined time period on basis of a present energy storage level and second environment light data, which second environment light data comprises the weather forecast data and the local day-light data; and —determining the lighting output profile on basis of the lighting demand and the battery capacity under consideration of keeping the energy storage level above a predetermined minimum level during the predetermined time period.