Premium Efficiency Motors

Electric motor systems consume large amounts of electrical energy and can provide an opportunity for significant energy savings. Energy represents more than 97% of total motor operating costs over its lifetime. However, the purchase of a new motor often tends to be driven by price, rather than the electrical energy it will consume.

Even a small improvement in efficiency could result in significant energy and cost savings. Investing a little more money upfront for a more efficient motor is often paid back in energy savings.

Motor Load

Motor efficiency varies with load. The efficiency of motors typically peaks at close to 75% of full load and is relatively flat between 50 and 100% load point. (See Graph 1)

Graph 1

Oversized motors have a lower rate of efficiency when in operation. A motor that is operating at a 35% load is less efficient than a smaller motor that is matched to the same load.

Power Factor

When motors operate near their rated load, the power factor (PF) is high. For lightly loaded motors (under 60% full load) the PF drops significantly. (See Graph 2)

Graph 2

When a motor is over-sized and lightly loaded, the PF will be lower compared to a motor that is properly sized. A facility with many induction motors and a low PF may address this issue by replacing motors with "premium-efficiency" motors that are properly sized.

Premium Efficiency Motors

In the motors marketplace, three different terms are used to label motors: " high-efficiency ", " energy-efficient " and " premium-efficiency ". Only the last two terms have definitions established by the National Electrical Manufacturers Association ( NEMA ). NEMA is a trade association that establishes standards to help in the selection and application of electric motors and other electrical equipment. In 2001, NEMA launched NEMA Premium™ Efficiency Electric Motors Program, which sets minimum efficiency levels for different motor types and sizes.

Table 2 in the PDF below was created in 2003 to compare various sized motors. The comparison is based on replacing an in-service standard-efficiency motor with a motor that meets the efficiency requirements for premium-efficient designations. All motors are 230V/460V, 1800 rpm (4 pole), TEFC, general purpose, NEMA Design A or B types. Cost comparisons are based on 7,500 annual hours at 75 percent of rated power (load factor = 75%), and a $0.06/kWh utility rate. A dealer discount of 20 percent was assumed for the purchase price.


If energy-efficient motors are misapplied, they may not achieve predicted energy savings and may actually result in diminished performance and reduced motor life. When replacing a standard efficiency motor, a high efficiency motor with lower or equal full load speed must be selected to avoid the energy increase that may negate the predicted energy savings resulting from a higher efficiency.

Other Benefits

In addition to the energy savings, premium and energy-efficient motors offer other benefits. They are usually more reliable, last longer, have longer warranties, run quieter and cooler and produce less waste heat than their less efficient counterparts.

Premium and energy-efficient motors may, in fact, be better suited for variable speed drive use than their standard-efficiency counterparts. When purchasing a motor for use with a variable speed drive "inverter rated" should be specified.

More Information

For more information refer to the Fact Sheet on Premium Efficiency Motors (PDF) prepared for NRCan by Prism Engineering.

Launched in June 2004 by Natural Resources Canada, CanMOST is a software program that analyses and compares the efficiency of three-phase electric motors. With its database of over 43,000 motors, CanMOST calculates energy and electrical demand savings so you can make the most energy-efficient and cost-effective choice when it comes to buying motors for your industrial application.