Based on the Fukui-Ishibashi model (FI model), the energy consumption in the mixed traffic flow is investigated via considering three factors: maximum velocity, length of vehicle, and the ratio of the mixed traffic flow. Simulations and analyses indicate that the energy consumption of the mixed traffic flow with the same length and different maximum velocities is related to the slow maximum velocity and its ratio. The slower the maximum velocity and its ratiare, the more energy will be consumed. Moreover, for the mixed traffic flow with the same maximum velocity and different lengths of vehicle, the energy consumption is related to the ratio of mixed vehicles. Longer vehicles induce more energy consumption. For a mixed traffic flow with the different maximum velocities and lengths of vehicle, its energy consumption is determined by the ratio of the mixed vehicles and delay probability p. The energy consumption of FI model drops off suddenly and trends to zero at the maximum flow rate, where there exits a maximum peak, which is significantly different from the result from the NaSch model.