This research was performed at the warehouse of an Indonesian power plant operation and maintenance (O&M) company. This unit controls supply chain activities for non-production materials. Based on initial observations, it was found that the operator has exceeded working time. Thus, operators often worked outside of operational hours. This has an effect on a number of workloads as well as discrepancies in material stock information. The focus of this research is to evaluate the warehouse's operational performance. This study focuses on two main warehouse operations, namely inbound and outbound materials. A discrete event simulation method is used to solve the problem. Performance measurement is carried out using the Arena software. The findings show that RFID technology can improve operational tasks by reducing cycle times, enhancing utility, and increasing productivity