The hybrid electric system for commercial vehicles introduction, redefine the load profile cycle used to evaluate common rail system components. This redefinition is necessary as result of the internal combustion engine number of starts enhanced, due to shared working cycle between diesel engine and electric motor. This load profile is mandatory to validate the common rail system components regarding lifetime for all application, conventional vehicle or hybrid. This new requirement, engine start numbers, places the hybrid electric vehicle as worst case load cycle, when compared with already known commercial vehicles cycle. The aim is also present the representative differences between both load cycles, more focused on hybrid. It will also give additional importance in common rail system requirements, applied for hybrid electric vehicles, an overview of instrumentation for the load profile measurement and the hybrid vehicle measurement particularities.