A system in one embodiment includes a detection unit, a boil-off auxiliary power unit, and a controller. The detection unit is configured to detect a characteristic of a boil-off gas stream from a cryotank configured to hold a cryogenic fluid. The boil-off auxiliary power unit is configured to receive the boil-off gas stream and use the boil-off gas stream to provide auxiliary power to a vehicle system. The controller is configured to acquire information from the detection unit corresponding to the characteristic; determine, using the information acquired from the detection unit, an available boil-off auxiliary energy that is available from the boil-off auxiliary power unit; determine a mode of operation of the vehicle system; determine a required auxiliary energy for the vehicle system; and to operate the auxiliary power unit based on the available boil-off auxiliary energy, the mode of operation, and the required auxiliary energy.