In this paper, a multizone model is developed to investigate the performance of an economizer under all conditions. The model primarily determines the economizer’s distribution parameters under all conditions with a small computational cost. Both the steady-state and dynamic behavior are calculated. These results are shown to be accurate and reliable using a computational fluid dynamic (CFD) model and the operational data obtained from a 600 MW boiler unit in Hubei province, China. Additionally, the model is used to predict the distribution characteristics during some fault conditions.