There are three major steps to determine motor operation costs. First, use energy efficiency and required output power to calculate input power. Next, multiply the hours per year and input power to establish the energy usage. Finally, the energy usage and electrical rate are used to calculate the annual operating cost.
How to Calculate Cost
For example, a designer has a ½ hp motor (373 W) that is 70% efficient. This would require an input power of 533 W. If this motor were to be run 8 hours a day, 7 days a week, then the yearly number of hours would be 2,912 hrs. The annual energy usage at this duty cycle would be 1,552 kW-hrs. At an electrical rate of 12 cents/kW-hr, the annual operating cost would be $186.24.