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Minimum Efficiency Standards for Electric Motors

Section 313 of the Energy Independence and Security Act (EISA) of 2007 raised Federal minimum efficiency standards for general-purpose, single-speed, polyphase induction motors of 1 to 500 horsepower (hp). This new standard took effect in December 2010. The new minimum efficiency levels match FEMP's performance requirement for these motors.

As a result of this increase in mandatory minimum standards and combined with the lack of significant availability of motors exceeding these standards, FEMP is suspending the purchasing specification for electric motors. Federal buyers may select for purchase any motor that meets design requirements.

While there is no longer a performance requirement that Federal buyers must meet, FEMP recommends that Federal customers consider the following:

Variable Frequency Drives: Variable frequency drives (VFDs), the most common type of adjustable speed drives, can be used with motors to help lower energy costs. VFDs are electronic systems used to control motor speed by changing the frequency and voltage supplied to the motor. VFDs can result in substantial energy savings, especially for varying loads. Small reductions in speed can also yield substantial energy savings. For example, a 20% reduction in fan speed can reduce energy consumption by nearly 50%. Pump, fan, and compressor systems with variable loads should be considered for retrofit with VFDs.

Rewinding or Replacing Motors: Many users choose to rewind or repair motors when they fail, a practice that is more common with motors greater than 50 hp. Even though rewinding a motor costs less than buying a new one, for most applications with high annual hours of operation it is cost effective to replace a standard motor with a premium one. In many cases, it may be cost effective to replace a standard motor prior to failure with a NEMA premium motor.

Motor Decisions Matter provides guidance on motor replacement and rewinding. Once a new motor has been purchased, rewinding or repairing it, even at a quality service center, may degrade its efficiency slightly (0.5% to 1.0% per rewind is the common rule of thumb). Though it is generally not cost effective to rewind open drip proof (ODP) motors, rewinding is often a cost effective option for large (greater than 100 hp) totally enclosed fan cooled (TEFC) motors. The Electrical Apparatus Service Association (EASA) provides a list of motor service centers.