Pumps & Systems, Jun. 2014, by John Malinowski.

"Several years ago, the U.S. Department of Energy (DOE) conducted a technical study about how to raise “small” motors’ efficiency levels. After years of study, the Small Motor Rule was passed, covering General Purpose two-digit NEMA frame (and IEC equivalents), single- and three-phase, 1/4- through 3-horsepower motors in open enclosures. Totally enclosed, fan-cooled (TEFC) motors are not included. This regulation will take effect on April 9, 2015."