Modern electric power utilities are facing many challenges due to increasing power demand but the growth of power generation and transmission has been limited due to limited resources, environmental restrictions and right-of-way problems. These problems can be minimized by installing Flexible Alternating Current Transmission System (FACTS) devices in modern electric utilities to optimize the existing transmission system. Most effective use of the FACTS devices depend on the fact, how these devices are placed in the power system, i.e. the location and size. An optimal location and size of FACTS devices allows controlling its power flows and thus enhances the stability and reliability of the power systems. In this paper, Firefly Algorithm (FA) and BAT Algorithm (BAT) have been applied and compared to determine the optimal location and size of Static VAR Compensator (SVC) in a power system to improve voltage stability subjected to minimize the active power losses, fuel cost, branching loading and voltage deviation. The effectiveness of the proposed algorithms and improvement of power system stability has been demonstrated on IEEE 57 bus system using fast voltage stability index. The results obtained with variation of parameters of Firefly and BAT Algorithms has been studied and compared with Genetic Algorithm. The results are presented and analyzed.