Energy-saving method for a wireless device in a telecommunication network which complies with the IEEE 802.11 standard, the method comprising the following steps: a) receiving, in said wireless device, at least one part of a data transmission, wherein said part comprises information concerning the frame length contained in the physical-layer header, a duration field contained in the link-layer header, recipient address and transmitter address of said transmission; and without waiting for the reception of the rest of the data transmission to end, b) determining compliance with a first set of conditions which at least comprises determining, according to the recipient address, that the transmission is not addressed to the device; and determining, according to the transmitter address, that the transmission originates from the same network to which the device belongs; c) in the event that the first set of conditions is complied with, determining compliance with a second set of conditions which at least comprises determining that the network is in a contention period, based on determining that the network is not in a contention-free period demarcated by an initial beacon frame and another final beacon frame; determining that the data received is not a CTS "clear to send" frame; and determining if the value of the duration field is less than or equal to a maximum value of 32767 microseconds; d) in the event that the first set of conditions is complied with, determining whether a sum of times exceeds a minimum shutdown time previously established according to hardware limitations of the device, wherein said sum of times comprises at least: - the time of duration of the rest of the data transmission plus a previously established minimum interframe interval; and - in the event that the second set of conditions is complied with, the value of the duration field; and wherein the minimum shutdown time comprises: a minimum shutdown time the device takes to shut down after a shutdown instruction is sent thereto; a minimum startup time the device takes to start up after a startup instruction is sent thereto; and a minimum preparation time the device takes to be ready to transmit or receive data; and e) in the event that the sum is greater than said minimum shutdown time previously established according to hardware limitations of the device, performing a micro-shutdown of the device with a duration equal to the value of said sum of times. a) receiving, in said wireless device, at least one part of a data transmission, wherein said part comprises information concerning the frame length contained in the physical-layer header, a duration field contained in the link-layer header, recipient address and transmitter address of said transmission; and without waiting for the reception of the rest of the data transmission to end, b) determining compliance with a first set of conditions which at least comprises determining, according to the recipient address, that the transmission is not addressed to the device; and determining, according to the transmitter address, that the transmission originates from the same network to which the device belongs; c) in the event that the first set of conditions is complied with, determining compliance with a second set of conditions which at least comprises determining that the network is in a contention period, based on determining that the network is not in a contention-free period demarcated by an initial beacon frame and another final beacon frame; determining that the data received is not a CTS "clear to send" frame; and determining if the value of the duration field is less than or equal to a maximum value of 32767 microseconds; d) in the event that the first set of conditions is complied with, determining whether a sum of times exceeds a minimum shutdown time previously established according to hardware limitations of the device, wherein said sum of times comprises at least: - the time of duration of the rest of the data transmission plus a previously established minimum interframe interval; and - in the event that the second set of conditions is complied with, the value of the duration field; and wherein the minimum shutdown time comprises: a minimum shutdown time the device takes to shut down after a shutdown instruction is sent thereto; a minimum startup time the device takes to start up after a startup instruction is sent thereto; and a minimum preparation time the device takes to be ready to transmit or receive data; and - the time of duration of the rest of the data transmission plus a previously established minimum interframe interval; and - in the event that the second set of conditions is complied with, the value of the duration field; e) in the event that the sum is greater than said minimum shutdown time previously established according to hardware limitations of the device, performing a micro-shutdown of the device with a duration equal to the value of said sum of times.