Why Variable-Speed Drives (VFDs)?

How VFDs reduce energy by matching load to speed (not just on/off or dampers).

10 min read · Jacob Willis, Net Zero Lead · Last reviewed July 2026

Most pumps and fans don't need full output most of the time, yet without a drive, a motor only knows how to run flat-out. A variable-frequency drive (VFD) lets the motor slow down to match the actual demand, and because of one remarkable piece of physics, slowing down saves far more energy than intuition suggests.

In this lesson

01The cube law
02What this is worth in practice
03Where VFDs earn their keep, and where they don't