In the conditions of the power system centralized management the main task of electric power system (EPS) mode optimization was fuel consumption minimization. No limits on the fuel consumption amount were foreseen. In liberalized electricity market of relations between energy subjects the basic task of the EPS mode optimization is minimization of all expenses. Thus every electric power market participant tries to get maximal income from the activity. But indicated aims must be achieved taking into account different constraints like technological constraints, fuel constraints, emission constraints and other. This paper introduces EPS mode optimization algorithm aimed at decreasing the negative effect on the environment. The calculations of test EPS show possibility of practical application in the conditions of concrete EPS.