The results of a combined theoretical and experimental study of the kinetics of a hot-liquid energy-storage tank are presented. A physical model is developed which accurately describes the thermal stratification behavior in a storage tank. The governing differential equations are developed for the physical model. A numerical solution to the system of equations is presented. Some existing models were examined and the predicted results of each are discussed. The concepts developed can be used to predict the thermal stratification behavior in a storage tank under most conceivable operating conditions. These conditions include flow configurations at the top and the bottom of the tank which both have inversionary tendencies. Inversionary behavior could conceivably occur in both the top and the bottom regions of the tank during a combined storage and usage mode which might occur at non-peak storage hours. Although the work was done primarily for the utilization of solar energy, the results are not limited to such application. The results are more significant as a contribution to applied fluid dynamics.