Electric motors vary greatly in performance. The selection of energy-efficient motors for heating, ventilating and air conditioning equipment installed in renovation or new construction can result in greatly reduced energy consumption during their operational lifetimes. In converting electrical energy into mechanical energy, motors incur losses in several ways: electrical losses, iron (core) losses, mechanical (friction and windage) losses, as well as stray losses dependent on design and manufacturing. Energy-efficient motors reduce losses because of their better design, materials, and manufacturing. With proper installation, energy-efficient motors run cooler and thus can have higher service factors and longer bearing and insulation life.
Example of calculating energy cost savings from motor replacement:
Consider replacing a 20 horse power motor that operates 80 percent loaded for 8,760 hours per year where electricity costs 5.5 cents per kilowatt-hour. Assume efficiencies are 0.88 and 0.92 for standard and energy-efficient motors, respectively.
Standard motor
20 horse power multiplied by 0.80 multiplied by 0.746 kilowatts per 1 horse power multiplied by 8,760 hours per year multiplied by 0.055 cents per kilowatt hour divided by 0.88 equals $6,535 per year
Efficient motor: 20 hp multiplied by 0.80 multiplied by 0.746 kilowatts per 1 horse power multiplied by 8,760 hours per year multiplied by 0.055 cents per kilowatts hour divided by 0.92 equals $6,251 per year.
Savings:
$6,535 minus $6,251 equals $284 per year.