Current wireless networks prioritize spectral efficiency, however, energy efficiency has become crucial due to environmental, monetary, and device design considerations. The recently proposed Gearbox physical layer (PHY) approach dynamically switches between modulation schemes including corresponding transceiver front ends to optimize energy efficiency considering spectral availability and required data rates. The contribution of this work is the prediction of the energy-saving potential of a Gearbox-PHY with flexible front ends for linear amplitude modulation considering the power consumption of the analog front end, variable bandwidth usage, and transmission with sleep phases. Our results indicate that a Gearbox-PHY promises significant energy savings.