Abstract: Under deregulated environment, transmission networks are operated close to their constraints. In this situation, FACTS devices can be useful in secure system operation. The obtained benefits of these devices have not been quantified and distinguished. In this study, for the first time, a method is proposed to calculate the revenue share of each FACTS device in the network by considering the role of FACTS devices in congestion management, reliability improvement and voltage profile improvement. Moreover, this method provides suitable economic signals for optimal FACTS devices expansion planning. To verify the proposed method, a 9-bus power system has been simulated in MATLAB/Simulink and Optimization Toolboxes.