Engineering Notes by Oriental Motor

Carbon Output Calculation of Electric Motors

[fa icon="calendar"] Apr 22, 2022 2:18:22 PM / by Johann Tang

Johann Tang

Increasing power efficiency and minimizing the carbon footprint is the trend these days.  Do you know how to calculate CO2 emissions from your electric motors, and which types of motors emit less?

To calculate a motor's CO2 emissions, you need two things:

  • power consumption (kWh)
  • CO2-based emission factor (kgCO2/kWh) [published by the electric power supplier]


With the following formula, you can estimate a motor's CO2 emissions


■Formula for Calculating a Motor’s CO2 Emissions

Motor’s CO2 emissions (kgCO2)
= Motor's power consumption (kWh)* × CO2-based emission factor (kgCO2⁄kWh)


*Please inquire with the nearest branch/sales office or our Customer Support Center about the power consumption of each combination of AC motor + general inverter and brushless motor.


Each electric power supplier’s CO2-based emission factor in the “List of emission factors by electric power supplier” released by the Japanese Ministry of the Environment and Ministry of Economy, Trade and Industry is used.  For other countries, you'll have to find this information, but in the USA, power plants are required to provide this information.


TIP: What is the CO2-based emission factor for power in the USA?

In 2020, total U.S. electricity generation by the electric power industry of 4.01 trillion kilowatthours (kWh) from all energy sources resulted in the emission of 1.55 billion metric tons—1.71 billion short tons—of carbon dioxide (CO2). This equaled about 0.85 pounds of CO2 emissions per kWh.

This is an average value.  For more specific CO2 emissions factors, please refer to: 


For a 200 W AC motor with an inverter (VFD), the annual CO2 emissions will be 521 kgCO2 according to the formula above.


Power consumption (1,109 kWh⁄year) × CO2-based emission factor (0.470 kgCO2⁄kWh)
= CO2 emissions (521 kgCO2)


-Calculated at 12 hours of drive time per day, 300 operating days per year, and a CO2-based emission factor of 0.470 kgCO2/kwh.

-Example is for a general 200 W output BH Series 3-phase AC induction motor with inverter (VFD).

However, if a higher efficiency is desired, a brushless (DC) motor should be considered.


If you use a brushless motor with the same output of 200 W, you can reduce the annual CO2 emissions to 386 kgCO2 under the following conditions.  That's about 25% less than an AC motor.


Power consumption (821 kWh⁄year) × CO2-based emission factor (0.470 kgCO2⁄kWh)

= CO2 emissions (386 kgCO2)


-Calculated at 12 hours of drive time per day, 300 operating days per year, and a power–CO2-based emission factor of 0.470 kgCO2⁄kwh.

-Example is for a 200 W output BMU Series.


Here's a comparison:

Power Consumption
CO2 Emissions
AC Motor + Inverter
Brushless Motor + Driver


What does this mean?

What we're saying is that CO2 emissions can be reduced by 135 kgCO2 annually if a 200W AC motor and inverter (VFD) is replaced with a brushless motor system of equivalent specifications.  135 kgCO2⁄year is equivalent to one refrigerator’s annual CO2 emissions.*

*A 450 L capacity home refrigerator for 3 to 4 family members. (Source: The Ministry of the Environment’s Energy-Saving Product Replacement Navigation System Shinkyu-san)

Why are brushless motors more efficient?

Brushless motors use permanent magnets to strengthen the magnetic flux, so their loss is lower than AC motors.  The fact that they don't suffer from secondary copper loss is a major difference.  That makes brushless motors highly efficient and allows them to use less power to do the same job.  With higher efficiency, the motor size and weight can be reduced, which contributes to the conservation of natural resources.


Internal Structure
Motor Loss Type
AC Motor
AC motor internal structure
Motor Loss - AC Motors
Brushless Motor
Brushless motor internal structure
Motor Loss - DC Motors


By the way, electrically-commutated (EC) fans with an onboard brushless motors can also contribute to energy savings.  For an explanation of all the benefits offered by brushless motors, please contact our team.

Brushless motor vs AC motor efficiency

Compare Brushless Motors to Other Speed Control Motors



  • A motor’s CO2 emissions (kgCO2) can be calculated by multiplying the motor's power consumption (kWh) by the CO2-based emission factor (kgCO2⁄kWh).
  • High-efficiency, energy-saving brushless motors are efficient for reducing CO2 emissions.
  • Annual CO2 emissions can be reduced by the equivalent of one refrigerator by switching from an AC motor to a brushless motor.


Topics: AC Motors, Speed Control, BLDC Motors

Johann Tang

Written by Johann Tang

Johann Tang is a Product Specialist at Oriental Motor USA Corp. with over 15 years of knowledge and experience supporting applications of various types of electric motors, gearheads, actuators, drivers, and controllers.

    Please subscribe to our New Motion newsletter to be notified of product news and blog updates!

    Recent Posts

    New call-to-action
    New call-to-action
    Click me
    New call-to-action