Renewable energy sources (RES) are a promising low operating cost solution for utilities. Moreover, RES are environmental attentive solution since, it provides low carbon emissions. However, RES have several associated challenges such as its intermittence nature and the form of generated power. The unpredicted RES output power is a significant challenge for power system schedulers and operators. Many researches have proposed a few solutions to maximize the benefit of utilizing RES in the power network and reduce the negative operational impacts. In this paper, a solution of economic dispatch and unit commitment problem which includes conventional and RES is proposed. The IEEE 14 Bus system is used to model, investigate and validate the proposed solution. Four different scenarios that consider the integration of RES have been evaluated toward the minimum operation cost using a two-stage differential evolution algorithm. The first scenario considers the operation cost of the power system that has only conventional generators. While the second and third scenarios have considered the power system operation costs when replacing one of the conventional generators by photovoltaic (PV) and wind turbine (WT) plants, respectively. The last, scenario is a hybrid case that considers the integration of one PV plant and one WT farm instead of two conventional generators. The study outcomes show that the one-day operation cost of the hybrid scenario is the most expensive one. Whereas the one-day operation cost of the third scenario has the minimum operation cost over all other scenarios.