The automotive industry is racing to introduce some degree of hybridization into their product ranges. Since the term "hybrid vehicle" can cover a wide range of differing technologies and drivetrain topologies, this has led to a plethora of vehicles that call them "hybrid." This poses an interesting challenge for marketers to differentiate these vehicles from the incumbents.However, it is not just the marketers who are faced with challenges, the developers of such hybrid drivetrains are faced with a rise in technical complexity due to the wide range of operating modes hybridization introduces. As propulsive torque is being generated in more than one place in a hybrid vehicle, the transitions from conventional drive to electrically supported drive bring with them complex aspects of multi-dimensional system control.The challenge is to be able to implement hybrid technology in an existing drivetrain, while adapting the existing components as required. The functional variability of hybrid technology, however, permits a range of possible implementations and the control calibration tasks themselves need to be well structured concerning hand-over, traceability and robustness.The only way to manage this exploding complexity is to apply methodical approaches to the calibration task and employ partial test automation when developing hybrid vehicles. The key to handling the exploding complexity of hybrid drivetrains is to employ a systematic and methodical approach, which eliminates repeated loops of calibration effort.By combining special tools and methodologies used for calibration projects, AVL is able to achieve the client's calibration targets of driveability, CO₂ reduction, maximum battery lifetime, and safety in hybrid vehicles by both efficiency improvements and increased quality.