A method and system for allowing automatic provisioning of a LED lamp in a dimmer system. The dimmer powers the lamp through a switched AC line. A wireless link serves for information exchange between the dimmer and the lamp. When the lamp is turned on by the dimmer, it starts a short waiting period in which it expects to wirelessly receive from the dimmer a provisioning message including a dimmer identification, which it saves to identify dimming messages the dimmer. Another aspect of the invention is disclosed in the above dimmer system, wherein the lamp comprises a backup battery. The dimmer wirelessly informs the lamp upon voltage drops at its input caused by user OFF actions and/or by AC supply outage. The lamp is configured to assume backup mode only upon detecting, based on the above information, a voltage drop at its input caused by an AC supply outage.