### Estimating Electric Motor Operating Cost Per Year

Estimating Electric Motor Operating Cost Per Year

When determining the operating cost of a project, it is important to remember motor operating costs.
To determine these costs by using the following formula:
EMOC/YR = (HP) (%FL) (0.746 HP KW) (\$/KWH) (HRS/YR)/MOTOR EFFICIENCY
Where
·                     Estimated Motor Operating Cost per Year = EMOC/YR
·                     Motor Horsepower = HP
·                     Motor Percentage of Full Load = %FL
·                     Horsepower to KW factor = 0.746
·                     Dollar per Kilowatt Hour = \$/KWH
·                     Motor Operating Hours per Year = HRS/YR

Example
For an example use the following variables to determine an estimated motor annual operating cost:
·                     Motor Horsepower = 200
·                     Motor Percentage of Full Load = %FL (you will need to estimate this value)
·                     Dollar per Kilowatt Hour = \$0.07 (you will need to determine your rate)
·                     Motor Operating per Year = 8,232 HRS/YR (49 WEEKS x 7 DAYS/WK x 24 HRS/DAY)
·                     Motor Efficiency = 96.2%

Therefore
·         EMOC/YR = (200 HP) (0.85 FL) (0.746 HP KW) (\$0.07/KWH) (8,232 HRS/YR) / 0.962
·         EMOC/YR = \$75,965/YR, say \$76,000/YR FOR A 200 HP MOTOR
·         As reference, for efficiency ratings you can use the following table for NEMA 3-Phase premium TEFC motors operating at 1800 RPM:

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