In this research, we study mechanical hybrid system for automobile using flywheel and CVT. In this paper, we present the experimental motor-driven test results which imitated vehicle installation using energy recovery system consisted of flywheel and CVT, and propose the energy recovery efficiency of the system. We evaluated the characteristic of the mechanical energy loss of the recovery system by coast down operation. From the measured data and proposed energy recovery efficiency evaluation formulation, we evaluated the energy recovery efficiency of the recovery system.