Most industrial polyolefin resins are produced via solid catalyzed polymerization. As the exothermic reaction takes place, the catalyst/polymer particle energy balance becomes an important issue. If the heat of reaction is not properly removed by the surrounding fluid, temperature rises may occur leading to particle overheating, even under good macroscopic heat exchange conditions in the reactor. In this work, particle-overheating phenomena are modeled for an entire population of particles. A previously developed population balance approach was extended in order to include particle energy balance effects. By selecting reactor residence times and catalyst size as the main internal coordinates, the model is able to cope with different reactor types and multistage configurations. Simulation examples include the gas phase and liquid pool polymerization of ethylene and propylene in industrial reactors such as the Unipol, Novolen and Spheripol processes. Pre-polymerization, catalyst particle size distribution and residence time distribution effects are analyzed.