The influences on electrical efficiency are summarized as follows: The humidification of the air supply system influences electrical efficiency. The results in Figure 6 show that the electrical efficiency slightly decreases when the power load is increased. While changing the inhale humidity in the air supply system, the following results are observed: under a current load of 65 A and humidification of 30%, maximum power is measured at 3,024 W. Under a current load of 91 A and humidification of 29%, the power measures up to4,006 W. Under a current load of 119 A and humidification of 28%, maximum power is measured at 5,021 W. Therefore, when the load is increased, the required humidification in the air supply system is slightly decreased to adjust the water content in the internal PEM and the airway, thus maintaining a stable power output.