With the increasing proportion of renewable energy, the power grid needs to pay more and more cost to ensure the security and stability operation. Meanwhile the total generation costs are reduced with the falling cost of renewable generation. Distinguishing the use of the total power system costs can give the system operator a direct way to understand these changes. This paper proposes a practical usage division method of the life cycle cost of the power system, which aims to classify the total cost into four types-the environmental cost, the energy supply cost, the adequacy cost and the safety cost. The example analyses a real power system, and shows that the proposed method can provide a reliable and comprehensible reference for the qualitative analysis of power grid operation and development.