In 2012, Westar Energy collaborated with GP Strategies to develop an EtaPRO Induced Draft fan module with the goal of overcoming and predicting ID fan capacity limitations at its Jeffrey Energy Center. At Unit 3 of this power station, the module is used to predict the remaining unit generation based on ID fan capacity and alert the operating team when they are near the limits. Using the empirical data from the historian, EtaPRO determines where the fan is operating on its performance curve in real time and then calculates the remaining capacity by moving along the fan system resistance curve until it meets the zero degree Inlet Control Vane angle curve. The module development eventually resulted in uncovering fan design capacity deficiency at this unit. This paper demonstrates the initiation, development and the use of this EtaPRO module at the Westar Energy’s Jeffery generating station.