In this paper, an integrated simulation-based methodology demonstrating feasibility and performance of several electric-hybrid concepts is developed. Several advanced tools are coupled to define the specifications of each component of the hybrid powertrain, to select the most promising hybrid architecture and finally to assess the proposed powertrain with regard to CO2 and pollutants emissions.Concurrent minimization of NOx and CO2 emissions enables to find the best compromise to fulfil Euro 6 standards while lowering fuel consumption. This stage consists in an iterative co-optimization of the power split strategies between the electric drive and the Diesel engine and of the engine settings (injection pressure, EGR rate, etc.). The methodology combines optimal control laws and optimization methodology based on global statistical models using single-cylinder design of experiments. After several iterations, this method allows to find the optimal NOx/CO2 trade-off curve. This enables to choose those settings and power split laws that satisfy Euro 6 standards without a NOx-dedicated aftertreatment device, or using an SCR-type aftertreatment device (with higher raw NOx emissions), while simultaneously minimizing fuel consumption.The proposed methodology, combined with powerful tools, facilitates the optimization and the assessment of a large diversity of innovative drivetrains.