This article describes the different efficiency classes (EFF1, EFF2, EFF3, IE1, IE2, IE3, IE4, and IE5) of electric motors. So let’s begin with the definition of efficiency and efficiency class.
What is Motor Efficiency and Efficiency Class?
The efficiency of an electric motor is a performance parameter that indicates the maximum output of the motor with respect to the input. The efficiency class is a standard that is used to represent the efficiency of the motor. The different types of efficiency classes available in the market are EFF1, EFF2, EFF3, IE1, IE2, IE3, IE4, and IE5. Where, EFF1, EFF2, and EFF3 are the European efficiency classes, whereas IE1, IE2, IE3, IE4, and IE5 are the efficiency classes of motors defined by the International Electrotechnical Commission (IEC). While defining the EFF class of motors, the stray loss is considered as 0.5% of the total input power, whereas in the case of IE classes, the stray loss is first determined.
How the Efficiency Classes are Classified?
Classification of EFF Efficiency Classes:
In the case of EFF class, the efficiency testing of the motor is conducted according to IEC 60034-2-1:1996 standard. For example, for an electric motor of 4 kW and 2-pole, if the efficiency is equal to or greater than 87.6%, then the motor is categorized in the EFF1 efficiency class. If the motor efficiency is in the range of 84.2% to 87.6%, then the motor will be in the EFF2 efficiency class. If the efficiency of the motor is less than 84.2%, then it will fall into the EFF3 efficiency class.
Classification of IE Efficiency Classes:
In the case of IE classes, the efficiency of the motor is determined as per the IEC 60034-30:2008 standard. For example, consider a 2-pole, 4 kW electric motor again, if the efficiency of the motor is 83.1%, then it is considered an IE1 class motor, if it is 85.8%, it is considered an IE2 class motor, if it is 88.1%, then the motor will be considered IE3 class, and if the efficiency is 90%, then the motor will come into the IE4 class.
Now, let us discuss each efficiency class one by one in detail.
What is EFF1 Motor Efficiency Class?
EFF1 stands for Energy Efficient Class 1. An electric motor of the EFF1 class will have an efficiency higher than that of the EFF2 and EFF3 class motors. When we observe the standard tables of three efficiency classes, it is found that EFF1 motors have an efficiency of 40% higher than that of the EFF3 motors and 20% higher than the EFF2 motors. EFF1 motors are usually designed and manufactured to run for more than 6000 hours per year.
Example – An electric motor of 30 kW and 4-poles having an efficiency greater than 93.2% is categorized as an EFF1 class motor.
What is EFF2 Motor Efficiency Class?
EFF2 stands for Energy Efficient Class 2. It is also known as Standard Efficiency Class or Improved Efficiency Class. The efficiency of the EFF2 class motor is 20% less than that of the EFF1 class motors. These motors are designed to run for more than 2000 hours per year.
Example – An electric motor of 30 kW and 4-poles having efficiency between 91.4% to 93.2% is categorized as an EFF2 class motor.
What is EFF3 Motor Efficiency Class?
EFF3 stands for Energy Efficient Class 3. It is the least efficiency class or below standard efficiency class in the European standard. The EFF3 class motors have very high power losses. These motors have an efficiency of 40% lower than the EFF1 class motors, and 20% lower than the EFF2 class motors.
In EFF3 motors, the high losses are due to large core size, poor quality copper wires, light loading of the motor, etc. These days, the EFF3 motors are not in use. EFF3 class motors are often designed to run for more than 1000 hours per year.
Example – An electric motor of 30 kW and 4-poles with an efficiency of less than 91.4% is categorized as an EFF3 class motor.
Therefore, in terms of efficiency, the efficiency classes EFF1, EFF2, and EFF3 are related as follows-
EFF1 > EFF2 > EFF3
EFF1, EFF2, and EFF3 Class Table
| Power in kW | 2-Poles | 4-Poles | |||
| EFF1 (Equal or above) | EFF2 (Equal or above) | EFF3 (Below) | EFF1 (Equal or above) | EFF2 (Equal or above) | EFF3 (Below) |
| 1.1 | 82.8 | 76.2 | 83.8 | 76.2 | |
| 1.5 | 84.1 | 78.5 | 85 | 78.5 | |
| 2.2 | 85.6 | 81 | 86.4 | 81 | |
| 3 | 86.7 | 82.6 | 87.4 | 82.6 | |
| 4 | 87.6 | 84.2 | 88.3 | 84.2 | |
| 5.5 | 88.6 | 85.7 | 89.2 | 85.7 | |
| 7.5 | 89.5 | 87 | 90.1 | 87 | |
| 11 | 90.5 | 88.4 | 91 | 88.4 | |
| 15 | 91.3 | 89.4 | 91.8 | 89.4 | |
| 18.5 | 91.8 | 90 | 92.2 | 90 | |
| 22 | 92.2 | 90.5 | 92.6 | 90.5 | |
| 30 | 92.9 | 91.4 | 93.2 | 91.4 | |
| 37 | 93.3 | 92 | 93.6 | 92 | |
| 45 | 93.7 | 92.5 | 93.9 | 92.5 | |
| 55 | 94 | 93 | 94.2 | 93 | |
| 75 | 94.6 | 93.6 | 94.7 | 93.6 | |
| 90 | 95 | 93.9 | 95 | 93.9 |
What is IE1 Motor Efficiency Class?
IE1 stands for International Efficiency Class 1. IE1 is the standard efficiency class as per the testing method of IEC 60034-30:2008. The IE1 class motor is the least efficient motor among the IE1, IE2, IE3, IE4, and IE5 classes.
Example – An electric motor of 30 kW and 4-poles having an efficiency equal to 90.7% is categorized as an IE1 class motor.
What is IE2 Motor Efficiency Class?
IE2 stands for International Efficiency Class 2. The IE2 class motor is a more efficient motor than IE1, but it is less efficient than IE3, IE4, and IE5 class motors.
Example – An electric motor of 30 kW and 4-poles having an efficiency of 90.3% is called as an IE2 class motor.
What is IE3 Motor Efficiency Class?
IE3 stands for International Efficiency Class 3. The IE3 class motor is a more efficient motor than IE1 and IE2 class motors, but it is less efficient than IE4, and IE5 class motors. IE3 is an international efficiency class or premium efficiency, class. In practice, in terms of power ratings, the IE2 and IE3 class motors are almost identical, but the cost of the IE3 class motor is about 10% higher than that of the IE2 class motors.
Example – An electric motor of 30 kW and 4-poles having an efficiency of 93.6% is called an IE3 class motor.
What is IE4 Motor Efficiency Class?
IE4 stands for International Efficiency Class 4. The IE4 class motor is a more efficient motor than IE1, IE2, and IE3 class motors, but it is less efficient than IE5 class motors. The IE4 class motors are also called super premium efficiency class. IE4 class motors are often manufactured on a demand only. These motors can be manufactured up to a power rating of 375 kW.
Example – An electric motor of 30 kW and 4-poles having an efficiency of 94.9% is called an IE4 class motor.
What is IE5 Motor Efficiency Class?
IE5 stands for International Efficiency Class 5. The IE5 class motor is the most efficient motor. IE5 class motor is currently the under-construction, i.e. the manufacturers are not allowed to produce IE5 motors. IE5 class motors have losses of 20% less than the IE4 class motors.
IE1, IE2, IE3, IE4 Efficiency Table:
| Power in kW | 2 Pole | 4 Pole | 6 Pole | 8 Pole | 2 Pole | 4 Pole | 6 Pole | 8 Pole | 2 Pole | 4 Pole | 6 Pole | 8 Pole | 2 Pole | 4 Pole | 6 Pole | 8 Pole |
| IE1 | IE1 | IE1 | IE1 | IE2 | IE2 | IE2 | IE2 | IE3 | IE3 | IE3 | IE3 | IE4 | IE4 | IE4 | IE4 | |
| 0.12 | 45 | 50 | 38.3 | 31 | 53.6 | 59.1 | 59.1 | 39.8 | 60.8 | 64.8 | 57.7 | 50.7 | 66.5 | 69.8 | 64.9 | 62.3 |
| 0.18 | 52.8 | 57 | 45.5 | 38 | 60.4 | 64.7 | 64.7 | 45.9 | 65.9 | 69.9 | 63.9 | 58.7 | 70.8 | 74.7 | 70.1 | 67.2 |
| 0.2 | 54.6 | 58.5 | 47.6 | 39.7 | 61.9 | 65.9 | 65.9 | 47.4 | 67.2 | 71.1 | 65.4 | 60.6 | 71.9 | 75.8 | 71.4 | 68.4 |
| 0.25 | 58.2 | 61.5 | 52.1 | 43.4 | 64.8 | 68.5 | 68.5 | 50.6 | 69.7 | 73.5 | 68.6 | 64.1 | 74.3 | 77.9 | 74.1 | 70.8 |
| 0.37 | 63.9 | 66 | 59.7 | 49.7 | 69.5 | 72.7 | 72.7 | 56.1 | 73.8 | 77.3 | 73.5 | 69.3 | 79.1 | 81.1 | 78 | 74.3 |
| 0.4 | 64.9 | 66.8 | 61.1 | 50.9 | 70.4 | 73.5 | 73.5 | 57.2 | 74.6 | 78 | 74.4 | 70.1 | 78.9 | 81.7 | 78.7 | 74.9 |
| 0.55 | 69 | 70 | 65.8 | 56.1 | 74.1 | 77.1 | 77.1 | 61.7 | 77.8 | 80.8 | 77.2 | 73 | 81.5 | 83.9 | 80.9 | 77 |
| 0.75 | 72.1 | 72.1 | 70 | 61.2 | 77.4 | 79.6 | 79.6 | 66.2 | 80.7 | 82.5 | 78.9 | 75 | 83.5 | 85.7 | 82.7 | 78.4 |
| 1.1 | 75 | 75 | 72.9 | 66.5 | 79.6 | 81.4 | 81.4 | 70.8 | 82.7 | 84.1 | 81 | 77.7 | 85.2 | 87.2 | 84.5 | 80.8 |
| 1.5 | 77.2 | 77.2 | 75.2 | 70.2 | 81.3 | 82.8 | 82.8 | 74.1 | 84.2 | 85.3 | 82.5 | 79.7 | 86.5 | 88.2 | 85.9 | 82.6 |
| 2.2 | 79.7 | 79.7 | 77.7 | 74.2 | 83.2 | 84.3 | 84.3 | 77.6 | 85.9 | 86.7 | 84.3 | 81.9 | 88 | 89.5 | 87.4 | 84.5 |
| 3 | 81.5 | 81.5 | 79.7 | 77 | 84.6 | 85.5 | 85.5 | 80 | 87.1 | 87.7 | 85.6 | 83.5 | 89.1 | 90.4 | 88.6 | 85.9 |
| 4 | 83.1 | 83.1 | 81.4 | 79.2 | 85.8 | 86.6 | 86.6 | 81.9 | 88.1 | 88.6 | 86.8 | 84.8 | 90 | 91.1 | 89.5 | 87.1 |
| 5.5 | 84.7 | 84.7 | 83.1 | 81.4 | 87 | 87.7 | 87.7 | 83.8 | 89.2 | 89.6 | 88 | 86.2 | 90.9 | 91.9 | 90.5 | 88.3 |
| 7.5 | 86 | 86 | 84.7 | 83.1 | 88.1 | 88.7 | 88.7 | 85.3 | 90.1 | 90.4 | 89.1 | 87.3 | 91.7 | 92.6 | 91.3 | 89.3 |
| 11 | 87.6 | 87.6 | 86.4 | 85 | 89.4 | 89.8 | 89.8 | 86.9 | 91.2 | 91.4 | 90.3 | 88.6 | 92.6 | 93.3 | 92.3 | 90.4 |
| 15 | 88.7 | 88.7 | 87.7 | 86.2 | 90.3 | 90.6 | 90.6 | 88 | 91.9 | 92.1 | 91.2 | 89.6 | 93.3 | 93.9 | 92.9 | 91.2 |
| 18.5 | 89.3 | 89.3 | 88.6 | 86.9 | 90.9 | 91.2 | 91.2 | 88.6 | 92.4 | 92.6 | 91.7 | 90.1 | 93.7 | 94.2 | 93.4 | 91.7 |
| 22 | 89.9 | 89.9 | 89.2 | 87.4 | 91.3 | 91.6 | 91.6 | 89.1 | 92.7 | 93 | 92.2 | 90.6 | 94 | 94.5 | 93.7 | 92.1 |
| 30 | 90.7 | 90.7 | 90.2 | 88.3 | 92 | 92.3 | 92.3 | 89.8 | 93.3 | 93.6 | 92.9 | 91.3 | 94.5 | 94.9 | 94.2 | 92.7 |
| 37 | 91.2 | 91.2 | 90.8 | 88.8 | 92.5 | 92.7 | 92.7 | 90.3 | 93.7 | 93.9 | 93.3 | 91.8 | 94.8 | 95 | 94.5 | 93.1 |
| 45 | 91.7 | 91.7 | 91.4 | 89.2 | 92.9 | 93.1 | 93.1 | 90.7 | 94 | 94.2 | 93.7 | 92.2 | 95 | 95.4 | 94.8 | 93.4 |
| 55 | 92.1 | 92.1 | 91.9 | 89.7 | 93.2 | 93.5 | 93.5 | 91 | 94.3 | 94.6 | 94.1 | 92.5 | 95.3 | 95.7 | 95.1 | 93.7 |
| 75 | 92.7 | 92.7 | 92.6 | 90.3 | 93.8 | 94 | 94 | 91.6 | 94.7 | 95 | 94.6 | 93.1 | 95.6 | 96 | 95.4 | 94.2 |
| 90 | 93 | 93 | 92.9 | 90.7 | 94.1 | 94.2 | 94.2 | 91.9 | 95 | 95.2 | 94.9 | 93.4 | 95.8 | 96.1 | 95.6 | 94.4 |
| 110 | 93.3 | 93.3 | 93.3 | 91.1 | 94.3 | 94.5 | 94.5 | 92.3 | 95.2 | 95.4 | 95.1 | 93.7 | 96 | 96.3 | 95.8 | 94.7 |
| 132 | 93.5 | 93.5 | 93.5 | 91.5 | 94.6 | 94.7 | 94.7 | 92.6 | 95.4 | 95.6 | 95.4 | 94 | 96.2 | 96.4 | 96 | 94.9 |
| 160 | 93.8 | 93.8 | 93.8 | 91.9 | 94.8 | 94.9 | 94.9 | 93 | 95.6 | 95.8 | 95.6 | 94.3 | 96.3 | 96.6 | 96.2 | 95.1 |
| 200 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.3 | 95.4 |
| 250 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.5 | 95.4 |
| 315 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.6 | 95.4 |
| 355 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.6 | 95.4 |
| 400 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.6 | 95.4 |
| 450 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.6 | 95.4 |
| 500 to 1000 | 94 | 94 | 94 | 92.5 | 95 | 95.1 | 95.1 | 93.5 | 95.8 | 96 | 95.8 | 94.6 | 96.5 | 96.7 | 96.6 | 95.4 |
Exemptions in IE Classes
The following exemptions are made in IE efficiency classes-
- The electric motors that have a number of poles equal to or greater than 10 are not classified into IE classes.
- The high-speed motors are not classified into IE classes.
- The electric motors permanently fitted with loads such as gearbox motors, etc. are not classified into IE classes.
- Brake motors, submersible motors, etc. are also not classified into IE classes.
Difference between IE and EFF Efficiency Classes
The following are the major differences between IE and EFF efficiency classes-
| S. No. | IE Efficiency Class | EFF Efficiency Class |
| 1. | Motor testing is conducted as per IEC 60034-2-1:2014 standard. | Motor testing is conducted as per IEC 60034-2-1:1996 standard. |
| 2. | Stray loss is measured. | Stray loss is assumed to be 0.5% of the input. |