The article discusses how to design cost-effective hybrid and fuel cell vehicles by optimizing the powertrain system. By using a computer tool called THEPS, the researchers simulate and optimize powertrain concepts based on various requirements and conditions. The goal is to minimize the operating cost of the vehicle by considering factors like fuel price and component wear. The approach involves choosing the type and size of vital components and determining energy management directives. The key finding is that a well-designed powertrain system can make hybrid vehicles more fuel-efficient and affordable, ultimately making them more competitive in the market.