This paper presents the study of power extraction and control of the electric power take off of a buoy type point absorber wave energy converter in heave. Two fundamental linear control strategies (the passive loading and optimum control) have been studied and their impacts on the sizing of generator were investigated. For the designed incident wave, a gearbox is needed to reach the rated speed of the generator. The generator is connected to the grid through a back-to-back converter which controls the electrical torque. Vector control technique is implemented to control the electric torque of the generator, by setting the direct axis current to zero. The results show that the current needed to control the electrical torque is too high for optimum control strategy. A method has been presented to reduce the power ratio significantly, but also with a decrease in average extracted power.