The purpose of this paper is to discuss the calculations of costs of power supply utilities for internal management purposes. To this end, we analyze the major phases of the value chain in the electric power sector, i.e. generation, transmission, distribution, and trading. The authors suggest ways to overcome the shortcomings and describe practical applications of the proposals. The methodology makes it possible to estimate the cost of each of these variables and then to aggregate them to show the costs per state and activity. Finally, a summary showing the operational performance in terms of revenue and costs per service, sales office, and estimated benefits paid, among others. The paper provides tools for recognizing departmental structures whose performance should be improved.