The large integration of DER into distribution system has significantly changed the approach to planning, design and operation of distribution networks. Based on the cost and benefits of three sides (distribution network owner, EDR provider, and electricity user), this paper proposes a elemental calculation approach to analysis the costs and benefits when DER is token as an alternative on network investment to meet special needs for special customer. A test example is used to verify the efficiency and effectiveness of the approach. (4 pages)