The picture of the five light gray cabinets to the right of the Generator control panel (green) are Variable Frequency Drives (VFD's) The control the pump motors stating and stopping and motor speed. Its allows a one pump to have a different flow range so that one pump can do the work of two. This saves power costs. This was installed in fall of 2012 at a cost of $180,000 (Click a picture to enlarge)