A method is provided which comprises: adjusting a plurality of times a transmit power to vary between a first setting and a second setting on a first Digital Subscriber Line (DSL line) to optimize energy consumption for the first DSL line; measuring or estimating a change in a performance of a second DSL line neighboring the first DSL line caused by a change in crosstalk on the second DSL line generated by the first DSL line in response to adjusting the transmit power of the first DSL line; and identifying one or more DSL lines among a plurality of DSL lines determined to safely operate in a low-power mode by identifying which of the plurality of DSL lines exhibit a crosstalk coupling to neighboring DSL lines below a specified threshold.