The power consumed depends on product of actual pressure(read on pressure guage and not set pressure) and injection speed. These parameters depend on geometry of part and viscosity of melt . If the connected power is lower,  than it may not be enough to fill larger parts of thin wall thickness(long flow ratio) even though the machine may have enough shot capacity. The lower connected power does not indicate consumption of power. It indicates lower capability for moulding bigger size of parts with large flow ratio. It defines the limitation of machine.