Unit commitment which is considered as a large scale, nonlinear, mixed-integer optimization problem plays a very important role in optimal operation of power systems. Solving the UC problem is a complex decisionmaking process since multiple constraints must be satisfied and a good UC solution method can substantially contribute to annual savings of production cost. In this paper combined economic environment unit commitment by using modified water evaporation optimization algorithm has been proposed. In order to show the feasibility of the proposed algorithm it has been tested with 10 unit system and the results are compared with existing method.