Approximately how much does it cost to operate a 10-horsepower (hp) motor continuously for a year?

A. \$3,000/year
B. \$5,000/year
C. \$7,000/year
D. \$9,000/year

Every professional working in a plant should be actively involved in the profitability of the plant and, as such, should know how much money will be saved by simply turning off a piece of equipment that is simply not needed at the time. With that in mind, any plant professional should be able to answer this question in 10 seconds or less — even if it is not within his or her area of expertise.

Let’s assume that a motor is 90 percent efficient and operates for 8,760 hours per year. Further, the incremental cost of electricity is \$0.07 per kilowatt-hour (kWh). Using these assumptions (they could be different in your location), the energy that a fully loaded 1-hp motor in continuous operation will consume is approximately (0.746 kW/hp / 0.90) * (\$0.07 / kWh) * 8,760 hours/year, or \$508/year.

Therefore, a fully loaded 10-hp motor would cost approximately \$5,080 per year to operate continuously. Answer B is the best answer using the above assumptions. Another answer might better apply in your location.