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April 25, 2015

How Variable Speed Motors Cut Down on Waste

Identifying areas of waste and finding ways to correct them is a proactive step in reducing global energy consumption. There seem to be many areas, though, and it can be difficult to pin any one thing down. However, the electric motor is one technology that is extremely prevalent. In 2011, the International Energy Agency (IEA) estimated that on a global scale, electric motor driven systems consumed nearly 50 percent of electricity production. Each year motors draw upwards of 7,000 terawatt hour (TW-h) and that is steadily increasing. The IEA further predicts that if this trend continues, by 2030 consumption could exceed 13,000 TW-h per year.

Motors: A breakdown

The majority of electric motors are less than 5 HP and are designed for commercial and home use. This is not where the majority of the energy is going though. Industrial processes that are powered by motors consume nearly two-thirds of total motor electricity usage. While 28 percent of all energy production in the U.S. is used in transporting people and goods, transport as a whole accounts for only about 3 percent of electricity used by electric motors. This could change in coming years though as electric drivetrains and hybrids increase in popularity.

This dominance that the motor maintains in the energy consumption arena marks it as an optimal target for reducing energy waste through efficiency increases. There are definitely ways to increase efficiency and reduce waste in motors that are used in the home as well, including improved air conditioners, heating systems, and water pumps.

Scaling back speed to minimize waste

Motors are typically designed to run at maximum capacity regardless of the job. Efficiency is one variable in the consumption game. Often the top performing motors and worst performing motors vary in efficiency by only a few percentage points. Over the lifetime of the motor this can translate to the accumulation of considerable savings, but the best place to start increasing efficiency and reducing waste is to prevent the motor from operating at its maximum capacity when it is not necessary.

A water pump is a prime example of this concept. There are times when the flow in the pump is only needed intermittently. Installing a valve will control the flow of water so that it is reduced, but that does not solve the problem of wasted energy since the motor is still running as if it is managing the maximum capacity of the pipe. In short, while the demand on the pump decreases, the motor never shifts to accommodate that downward turn. It does not run at a speed that is proportionate to the job at hand. This results in needless waste of energy.

Increased motor efficiency equals decreased energy waste

Variable speed technology is one proposed answer to the problem. While this technology does nothing to improve motor efficiency, it does improve overall system efficiency. In the example of the water pump, the system’s efficiency can be improved by introducing a variable speed drive to control the motor’s speed and, hence, the water flow rate. In fact, this would eliminate the need for the valve altogether since the motor could operate at slower speeds to achieve the desired variability in flow rate.


There is definitely room for improvement when it comes to motor system efficiency and waste. By improving efficiency, precious energy is saved, which translates into dollars saved. In certain applications, energy use can be reduced by 50 percent or more by simply installing variable speed drives to electric motors. This is a simple step in curbing waste. The initial costs to upgrade or modify these motors are offset by the savings – which can be significant. It is well worth the effort.