Systems and methods are provided for the use of systems that recover mechanical power from waste heat energy using multiple working expanders with a common working fluid. The system accepts waste heat energy at different temperatures and utilizes a single closed-loop circuit of organic refrigerant flowing through all expanders in the system where the distribution of heat energy to each of the expanders allocated to permit utilization of up to all available heat energy. In some embodiments, the system maximizes the output of the waste heat energy recovery process. The expanders can be operatively coupled to one or more generators that convert the mechanical energy of the expansion process into electrical energy.