A fuel cell power plant is provided for a mobile unit. The mobile unit is provided with a drive device (29) driving the mobile unit when supplied with electrical power. The power plant comprises a fuel cell (21) generating power when supplied with fuel, a battery (27) charged with power generated by the fuel cell, a power regulation device (31) selectively distributing power from the fuel cell (21) and the battery (27) to the drive device (29), and a controller (33) for controlling running operations. The controller (33) estimates the energy required to activate the fuel cell (21), and controls the power regulation device (31) when the energy required to activate the fuel cell is greater than or equal to a determination value so that the fuel cell is not activated and power from the battery (27) is supplied to the drive device (29).