This paper presents genetic algorithm-based post-outage voltage and reactive power calculations for transmission line and transformer outages. Deficiencies of the traditional sensitivity-based (linear) methods are overcome by formulation of a line outage as nonlinear constrained optimization problem for a bounded networks The proposed optimization problem is later solved for bounded network variables by genetic algorithms. The accuracy of the method is tested on IEEE 14-bus and IEEE 57-bus test systems. Simulation results are compared both with the results of a full power How study and with the results of the papers presented in the literature. The results have shown that the proposed method improves the accuracy of post-outage voltage and reactive power values with less computational effort.