Electrified vehicles represent mobility’s future, but they impose challenging and diverse requirements like range and performance. To meet these requirements, various components, such as battery cells, electric drives, fuel cells, and hydrogen vessels need to be integrated into a drive and storage system that optimizes the key performance indicators (KPI). However, finding the best combination of components is a multifaceted problem in the early phases of development. Therefore, advanced simulation tools and processes are essential for satisfying the customer´s expectation. EDAG Engineering GmbH has developed a flat storage platform, which is suitable for both, BEV and FCEV. The platform allows for the flexible and modular integration of batteries and hydrogen vessels. However, package space is limited and the impact of the design choices regarding the vehicle’s KPI need to be considered. Therefore, EDAG has developed a simulation model that combines automated 3D design and packaging for storage integration (battery cells and hydrogen vessels) with a simulation of the vehicle’s longitudinal dynamics. The model uses a cell database and automatically packages different cells into a predefined design space. For FCEV, it additionally packages hydrogen vessels in the remaining space. The model calculates the capacity and mass of each storage variant and uses them as input parameters for the vehicle longitudinal simulation. The main innovation of this contribution lies in the fact that it accounts for the 3D packaging of storage components enabling the analysis a multitude of design choices in the early concept phases and simulates their impact on the vehicle performance. Thus, decision-making processes in early development phases are supported and development time is significantly reduced. Within this contribution, two case studies for BEV and FCEV are performed investigating the influence of the package space provided for the energy storage on the vehicle performance and range highlighting the potential of the novel approach.