Power systems are getting more complex structure from production to consumption stages. The continuous, reliable, quality and economical delivery of electrical energy to the consumer depends on ensuring uninterrupted and optimized energy flow during the production/transmission/distribution stages. Optimum Power Flow (OPF) problem goals to optimize the parameters such as fuel cost, active/reactive power losses, etc by keeping the generators/ bus voltages, tap setting and active/reactive power within their secure limits. Therefore, it is important to optimize load flow in power systems with an effective method. This paper uses a recent heuristic algorithm, named as the Modified Water Cycle Algorithm (MWCA), for the OPF problem. For the purpose demonstrate the effectiveness of the recommended method, it has been analyzed on the IEEE 30 bus power system for varied object functions. The validity and flexibility of this algorithm are discussed by comparison with numerical conclusion of the many newly published heuristic methods in the literature. In this study, the result of the of fuel cost, which is important results of the IEEE 30 bus test system, is computed using MWCA as $798.9021/s. This value is best the fuel cost results of various methods reported in the study. In addition, this method, has applied to a part of the virtual model of 154 kV South Marmara transmission system to show that the active power losses of transmission system could be reduced in a realtime system.