This paper presents the calculation of the optimum installation angle for the fixed solar-cell panels based on the genetic algorithm (GA) and the simulated-annealing (SA) method. The output power of the solar-cell panel is highly affected by the sunlight incident angle and its efficiency can be improved if the solar-cell panel is properly installed with the optimum angle. The relationship between the sunlight incident angle and the sunlight radiation intensity on the solar-cell panel surface is also presented in this paper. Both GA and SA with climatic data are utilized to calculate the optimum installation angle of the solar-cell panel for different locations in Taiwan. The best monthly and annual installation angles obtained by computer simulations are presented. Hardware experimental results indicate that the actual best monthly installation angles are very close to the computer simulation results.