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Oversized motors running at less than full capacity are inefficient, and they can cost you on your energy bill.

Curt Arens, Editor, Nebraska Farmer

February 29, 2024

2 Min Read
Electric motor
HEAVY USE: Electric motors are everywhere on the farm — from grain handling, to irrigation, to livestock and feeding facilities. Having electric motors sized properly and running at full capacity saves on energy bills, compared to running an oversized motor at less than full capacity. Curt Arens

Is it better to have an oversized electric motor running at less than full capacity, or to have a properly sized motor running at an optimal level? The answer is easy, but putting that knowledge into practice around the farm isn’t always that simple.

Rick Stowell, Nebraska Extension animal environmental engineer, said during a recent University of Nebraska Center for Agricultural Profitability webinar on farm energy that farmers are often concerned about being underpowered, so they might go with a variable output motor for the operation.

However, this encourages producers to “go big” when they are installing electric motors for various operations. But running an oversized motor at a less-than-optimal load is an inefficient process, and it can ding producers on their energy bills, Stowell said.

Cost of operation

Related to large farm motors is the electrical cost of running them, and specifically, how motors affect electric bill charges.

The power factor, according to Nebraska Extension energy educator John Hay, is a ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA).

Apparent power is the demand — that amount of power used to run equipment over a specific period of time. On an energy bill, the closer the power factor is to 1.0, the better, because it means that all the energy supplied by the provider is being consumed by the load. The lower the power factor, the less efficient the system is running, potentially leading to higher energy bills through power factor charges.

In real terms on the farm, Hay said that this means the power factor is highest when a motor is running at full capacity or close. “Running at partial capacity, the power factor is worse,” he added.

Energy providers use the power factor in determining the bill, so oversized motors running at less than full capacity can cost more to operate in the long run, he explained.

Irrigation systems

“Having too much power is a problem in many irrigation systems, for instance,” Hay said. “I can see where it happens. A motor goes out and maybe there is an oversized motor sitting on the shelf at the irrigation supplier, so you take that one home.”

But producers can get hit twice under this scenario because they are operating inefficiently with a motor that is oversized and running at less than full capacity, plus the power factor is worse with oversized motors, so they are hit with a higher bill by the energy provider. That’s why sizing motors to the operation is so important, Hay said.

Learn more by emailing Hay at [email protected], or Stowell at [email protected].

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About the Author(s)

Curt Arens

Editor, Nebraska Farmer

Curt Arens began writing about Nebraska’s farm families when he was in high school. Before joining Farm Progress as a field editor in April 2010, he had worked as a freelance farm writer for 27 years, first for newspapers and then for farm magazines, including Nebraska Farmer.

His real full-time career, however, during that same period was farming his family’s fourth generation land in northeast Nebraska. He also operated his Christmas tree farm and grew black oil sunflowers for wild birdseed. Curt continues to raise corn, soybeans and alfalfa and runs a cow-calf herd.

Curt and his wife Donna have four children, Lauren, Taylor, Zachary and Benjamin. They are active in their church and St. Rose School in Crofton, where Donna teaches and their children attend classes.

Previously, the 1986 University of Nebraska animal science graduate wrote a weekly rural life column, developed a farm radio program and wrote books about farm direct marketing and farmers markets. He received media honors from the Nebraska Forest Service, Center for Rural Affairs and Northeast Nebraska Experimental Farm Association.

He wrote about the spiritual side of farming in his 2008 book, “Down to Earth: Celebrating a Blessed Life on the Land,” garnering a Catholic Press Association award.

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