The higher the input power of the DC prime mover the higher the efficiency and the lower the input power the lower the efficiency.The lower the power input of a DFIG the bigger the efficiency and the bigger the input power the smaller the efficiency. The efficiency of a doubly fed induction generator is determined by a number of factors but the installation of capacitors banks so that they can produce the reactive power needed for the motor to give it a starting torque and hence reducing on the input power while the efficiency will be still improved hence energy will be saved.