Previous work by one of the authors entailed modeling of a packed bed thermal energy storage system utilizing phase-change materials (PCM). A principal conclusion reached is that the use of a single family of phase-change storage material may nor in fact produce a thermodynamically superior system relative to one utilizing sensible heat storage material. This paper describes the model constructed for the high-temperature thermal energy storage system utilizing multiple families of phase-change materials and presents results obtained in the exercise of the model. Other factors investigated include the effect on system performance due to the thermal mass of the containment vessel wall and variable temperature of the flue gas entering the packed bed during the storage process. The results obtained indicate efficiencies for the system utilizing the five PCM families exceeding those for the single PCM family by as much as 13 to 26 percent. It was also found that the heat transfer to the containment vessel wall could have a significant detrimental effect on system performance.