A method for transmitting energy to a plurality of receiving nodes using a plurality of antennas includes: acquiring residual energy information of the receiving nodes and channel information between the antennas and the receiving nodes; determining a beamforming weight indicating a ratio between signals transmitted from the antennas and an awake ratio indicating a probability that the receiving nodes are in an active state to receive signals, based on the residual energy information and the channel information of each of the receiving nodes; generating beacon signals corresponding to the antennas based on either one or both of the beamforming weight and the awake ratio; and transmitting the beacon signals through the antennas.