Using hybrid power systems on diesel multiple units (DMUs) reduces the cost of fuel and energy resources, reduces harmful emissions, and lowers noise levels. An important task, the solution of which determines the efficiency of a hybrid power unit, is to determine the rational modes of its operation, which are used to create energy management strategies. To determine the source from which it is necessary to power the systems of a DMU, it is proposed to use the concept of “comparative fuel consumption”. This concept determines how much fuel is consumed to produce one kWh of energy consumed by the DMU systems, considering losses in the elements of a hybrid power unit. The paper considers the option of powering the DMU systems directly from the diesel generator and from the storage device, which was previously charged from the diesel generator. It is shown that in the latter case, the equivalent comparative fuel consumption is estimated to be 20% higher than the comparative fuel consumption in the mode of power supply directly from the diesel generator. Using the case of the DEL-02 DMU, it is shown that it is advisable to power its systems at the zero and the first positions of the driver controller from an energy storage device that has been charged from a diesel generator. The results obtained are relevant to use for developing energy management strategies for rolling stock equipped with hybrid power units.