Economic load dispatch (ELD) is one of the important problems of power system operation. Conventional methods like Lambda iteration method are not efficient for complex ELD problems. Particle swarm optimization is preferred in ELD problem due to its high performance. The Inertia Weight PSO and Constriction Factor PSO algorithms are performed on three-unit and six-unit systems. The analysis of ELD problem is performed by Conventional method and PSO method. In this paper, losses are neglected in the ELD problem. PSO algorithm obtains the best solution for ELD problem.