This paper proposes a new hybrid optimization method for solving a hydrothermal coordination problem. In general, the problem is decomposed into smaller hydro and thermal sub-problems which are solved separately. The hydro sub-problem is solved by the peak shaving method using the proposed hybrid optimization method. It combines genetic algorithms with the traditional numerical optimization method. The hybrid method has been applied to a real hydrothermal system, i.e., the Slovak power system. The results have proved the efficiency of the proposed method.