While adding a variable frequency drive to an AC induction motor will allow speed control, it will not be as efficient as the speed control of an EC motor. The chart on this slide depicts the percentage of the input power of a VFD (red) vs. and EC motor (green). The chart is shown in 10% speed increments starting at 20% motor speed. As can be seen, over the entire speed range the EC motor shows a significant power savings over the AC/VFD solution.