Telecommunications equipment are moving from the large Central Offices where the source of energy (AC Mains or DC batteries) is accessible towards more distributed equipment along the network where AC Mains can not be accessible. To supply energy in an optimum way to these equipment, called Remote Units, is a new challenge for telecommunication companies affecting this selection to the cost and reliability of the overall telecom system. The target of this paper is to propose a procedure to select the most suitable solution from the cost point of view.