Methods and systems of optimizing efficiency of a motor drive or generator are provided. The methods include measuring data corresponding to input power and output power of a motor drive or generator at a control parameter and different load values. The methods include generating a three-dimensional surface model based on the measured data. The three-dimensional surface model can estimate an efficiency of the motor drive or generator at the control parameter and at unmeasured load values. The methods can include determining optimal efficiency of the motor drive or generator at the different load values and the unmeasured load values based on the three-dimensional surface model.