The big savings come from proper impeller sizing, proper RPM, and proper sizing.
Some things to keep in mind: 1) New mixing designs can make immense energy savings over previous designs. I've seen the incredible advancements in mixer efficiency, and I've also seen tremendous waste and difficulty due to archaic specifications and poor assumptions. Disclaimer: I work for a major mixer OEM. If it's at all practical, consider having the manufacturer guarantee the results. Unless your electricity is free and your performance is not important, the performance spec is a requirement.
