A powered device (PD) receives a Power-over-Ethernet (PoE) voltage to power the PD over a cable from Power Source Equipment (PSE) configured to output a requested one of multiple candidate PoE voltages to the cable. The PD determines a preferred PoE voltage among the multiple candidate PoE voltages that minimizes a total power loss due to (i) the cable, and (ii) a power loss of the PD that would result if the PD were powered through the cable. The PD requests the preferred PoE voltage from the PSE, receives the preferred PoE voltage from the PSE, and operates at the preferred PoE voltage.