CASE STUDIES
Motor Efficiency Classes Explained: IE1 to IE4
What are motor efficiency classes?
Motor efficiency classes are a standard way of ranking how well an electric motor turns the electrical power it draws into useful work. They are set by the international standard IEC 60034-30-1, which sorts motors into IE classes, short for International Efficiency. The higher the class, the less energy the motor wastes as heat, and the lower its running cost over time. The standard runs from IE1 up to IE4.
The IE classes
IEC 60034-30-1 defines the classes as a ladder, each step more efficient than the last:
| Class | Name | Nominal efficiency, 7.5 kW motor, 4 poles, 50 Hz |
|---|---|---|
| IE1 | Standard efficiency | 86.0% |
| IE2 | High efficiency | 88.7% |
| IE3 | Premium efficiency | 90.4% |
| IE4 | Super premium efficiency | 92.6% |
The figures above are for one motor size, because the exact efficiency figure for any motor depends on its power rating and its speed. A 0.75 kW motor and a 200 kW motor of the same class have different numbers. Higher efficiency motors also tend to be bigger and longer than a lower class motor of the same power, which is worth checking against the space available.
Why the class matters
The class matters for two reasons: cost and regulations.
- Running cost. For a motor that runs long hours, the electricity it uses over its life can cost more than the motor itself. How much more depends on how heavily it is used. Using a higher efficiency motor means less energy for the same output, which makes a noticeable difference to the energy bill on a drive that runs continuously.
- Regulations. Many governments set minimum energy performance standards, often called MEPS, that require new motors to meet at least a given IE class. Singapore, for example, requires standalone motors above 0.75 kW to be IE3 or higher. Where a rule like this applies, a lower class is not an option to weigh up on cost. It cannot be supplied.
Where the class is marked
Efficiency classes appear on a motor's nameplate and in its datasheet, marked IE1, IE2, IE3 or IE4. When a machine is specified or a motor is replaced, the class is one of the details to check alongside the power rating and the speed.
The IE standards are the same across manufacturers, so an IE3 from one maker meets the same efficiency limits as an IE3 from another. Depending on the market and the supplier, however, you may have to convert an IE1 motor to an IE2, IE3 or higher efficiency motor when you replace it.
To see the geared motors AVM supplies, visit the geared motor category.
Frequently asked questions
What do IE1, IE2, IE3 and IE4 mean?
They are efficiency classes from the standard IEC 60034-30-1. IE1 is standard efficiency, IE2 high, IE3 premium and IE4 super premium. A higher class wastes less energy as heat.
What is the difference between IE3 and IE4?
IE4 loses less energy than IE3. On a 7.5 kW four-pole motor at 50 Hz, the nominal efficiency is 90.4% for IE3 and 92.6% for IE4.
What efficiency class does Singapore require?
Standalone motors above 0.75 kW have to be IE3 or higher.
Why does motor efficiency matter?
On a motor that runs long hours, the electricity it uses over its life can cost more than the motor did. A higher class lowers that running cost, and in many markets a minimum class is required by law.
Are higher efficiency motors bigger?
They tend to be bigger and longer than a lower class motor of the same power, so check the space and the mounting before replacing one.
Where do I find a motor's efficiency class?
On the motor's nameplate and in its datasheet, marked IE1 to IE4, alongside the power rating and the speed.