Demands for new features, increasing electrical loads, and improved fuel-economy are driving development of 42V PowerNets in automobiles. Shorter design cycles, increased complexity and a focus on quality are making robust design processes a strategic advantage for competitive manufacturers. Hardware prototypes are both time-consuming and inadequate for the task of verifying performance over a broad range of operating modes, environmental conditions and part-to-part variations. This paper outlines the use of an advanced design-flow, from idea to manufacturing, for vehicle power systems. It starts with the analysis of different topologies down to the subsystem modeling of a power window system. Finally it integrates everything to a Digital Mock-Up (DMU) and analysis of the entire system. Dynamic interactions among the various supplies, converters and loads are examined. System stability and performance are assessed under normal and extreme operating conditions.