The short-term optimization problem is how to schelude generation to minimize the total fuel cost or to maximize the total profit over a study period of typically a day, subject to a large number of constraints that must be satisfied. The most important constraint is that the total generation must equal the half-hourly forecast demands for electricity. There are two related short-term optimization problems, “unit commitment” and “economic dispatch”. This paper includes knowledge of economic dispatch and solution techniques with or without transmission losses. In the optimal economic dispatch solution, losses have very important roles. Choosing generator units is one of them.