A method for managing energy to a transport climate control system from a vehicle electrical system is provided. The vehicle electrical system includes a vehicle power network and an auxiliary power network connected to a transport climate control load network via a DC regulated bus. The method includes monitoring a vehicle voltage of the vehicle power network and determining whether the vehicle power network requires holdover assistance based on the vehicle voltage. Also, the method includes the bus sending vehicle power energy generated by the vehicle power network to the transport climate control load network without assistance of the auxiliary power network when the controller determines that the vehicle power network has sufficient power capacity available, and the bus sending the vehicle power energy and auxiliary power energy stored by the auxiliary power network to the transport climate control load network when the controller determines that the vehicle power network requires holdover assistance.