Reducing Peak Demand
Variable frequency or variable speed drives have a great ability to reduce energy costs. The drives work by slowing the speed of electric motors to meet variable demand. Savings are dependent on the variability of the load serviced by the electric motor. But in general, if you run a motor at half speed you can save 87.5% of the electrical energy.
VFDs can work with any electric device driven by an electric motors including pumps, fans, and compressors.