The coal shortage in the stockpile of the coal-fired power plant will possibly stop the power plant operation, which leads to negative impact to the company's operational performance as well as the interconnected electrical power system. Coal inventory is usually stored in the stockpile with an excess amounts to maintain service level. But the excessive level of coal would make a financial burden in terms of storage and maintenance costs. The objective of this study is to plan the optimum coal safety stock level in XYZ coal-fired power plant so it could serve the system with the low cost of inventory without affecting the operation reliability. The results showed that continuous review policy was more suitable to calculate coal inventory than periodic review policy because it stored less coal and limited stockpile capacity in the power plant. This scenario could reduce the cost of coal inventory planning up to ∼ 14%.