It is shown that to maximize the power output of a power plant is equivalent to minimizing the total entropy generation rare associated with the power plant. This equivalence is illustrated by using two of the oldest and simplest models of power plants with heat transfer irreversibilities. To calculate the total entropy generation rare correctly one must recognize that the optimization process (e.g., the variability of the heat input) requires ＇＇room to move,＇＇ i.e., an additional, usually overlooked contribution to the total entropy generation rate.