IE stands for International Efficiency. The classes are set out in the international standard IEC 60034-30-1, and they exist so that everyone is measuring the same thing: how much of the electricity going into a motor comes back out as useful work, and how much is lost as heat.
The scale runs from IE1 at the bottom to IE5 at the top. The higher the number, the lower the losses. In day-to-day work, the four you will meet are:
One thing to be clear about: the rating says nothing about how much power a motor produces. A 22 kW motor delivers 22 kW whether it is IE2 or IE4. What changes is how much electricity it draws to do it. A higher class means the same job for less power.
People often expect a big gap between the classes and are surprised by the figures. On a typical mid-sized four-pole motor, the difference between an IE3 and an IE4 unit can be little more than a percentage point of efficiency. On paper that looks trivial.
The losses tell a different story. Each step up the scale cuts a motor's losses by roughly 15 to 20 percent. On a motor that runs long hours, that is where the money is. The improvement is largest on smaller motors and narrows on the very big ones, because large motors already run close to the practical ceiling.
This is where efficiency stops being a preference and becomes law. The requirements have tightened in stages, and the main points are these:
There are genuine exemptions too. Brake motors, many explosion-protected (Ex) types and various specialist designs sit outside parts of the regulation.
Here is the part that often gets misunderstood, and it matters. The regulation controls motors being placed on the market, meaning new motors being sold or put into service. It does not force you to scrap motors you already own, and it does not stop you repairing them. Rewinding an existing motor, even an older IE1 or IE2 unit, is perfectly legal and does not trigger the new-motor requirement. The industry trade body, the AEMT, is clear on the point: a lower-efficiency motor can be repaired and reused, while the regulation governs what a new motor must achieve. The rules even exempt spare-part motors on purpose, so that existing equipment can be kept running rather than scrapped early.
So as a buyer, you are not the one carrying the compliance risk. A reputable supplier will not sell you a non-compliant new motor in the first place. For most operators the real question is rarely whether something is legal. It is which option keeps the machine running for the lowest cost over time.
Higher-class motors cost more to buy. That is the part that makes people hesitate, and it is fair enough. But the purchase price is a small share of what a motor costs over its life. For a motor that runs more or less continuously, the great majority of the lifetime cost is the electricity it uses. The price on the invoice barely registers next to it.
Seen that way, a more efficient motor pays you back a little every hour it runs. On a hard-working unit, the extra cost of a higher class is usually recovered through lower energy bills within a few years, and everything after that is saving.
Two things move that sum more than anything else: how many hours a year the motor actually runs, and what you pay per unit of electricity. A motor that runs a few hours a week is a very different case from one that never stops. That is why a blanket rule rarely fits, and why it is worth doing the sum on the specific motor rather than the general principle.
There are side benefits as well. A more efficient motor turns less energy into waste heat, so it tends to run cooler and last longer. Lower consumption also means lower carbon, which counts for more and more with businesses that have targets to hit.
This is one of the questions we hear most in the workshop, and it is a sensible one to ask. The answer depends entirely on how the rewind is done. A poor rewind, especially one that overheats or damages the stator core when the old windings are removed, can take a small amount off a motor's efficiency. Done badly, it can quietly undo the premium you paid for an efficient motor in the first place.
Done properly, it does not. The joint study by EASA and the AEMT, which is the reference work on this, found that a rewind carried out to recognised good-practice procedures keeps a motor's efficiency, even after repeated rewinds. The average change measured was a fraction of a percent, well inside normal tolerance, and those procedures are now built into the international repair standard. In some cases, an older, less efficient motor can even come back from a rewind running better than it did before.
What it comes down to is the workshop. Controlled burn-out temperatures, careful handling of the core and disciplined winding are what keep an efficient motor efficient. A rewind is only ever as good as the people doing it.
Whether you are replacing a motor or weighing up a repair, the efficiency class is one piece of the picture rather than the whole of it. Every motor that comes to us gets a fair appraisal and an honest report on the best line of action. Sometimes that is a rewind, carried out to good-practice standards so the efficiency is kept, and tested before it leaves us. Sometimes it genuinely works out cheaper to fit a new motor, and we will tell you when that is the case.
We supply AC and DC motors built to current efficiency standards, we rewind and repair motors, pumps, fans and gearboxes, and where the wider aim is to cut running costs across a site, our energy-saving work can help pinpoint where the best returns are.
We are based in Leicester, just off the M1, and cover the East Midlands, collecting and returning jobs. Our line is answered around the clock for breakdowns.
An IE rating is not box-ticking. It tells you what you can fit, and what a motor will cost to run long after the invoice is paid. For most new three-phase motors, IE3 is now the minimum, and for the larger sizes, it is IE4. For a motor that earns its keep running long hours, moving up a class is usually one of the easier energy decisions a business can make.
But the rules do not mean scrapping what you already have. A working motor can stay in service, and a well-run rewind keeps an efficient motor efficient. The right answer depends on the motor in front of you: its age, its condition, how hard it works and what it costs to run. Get that assessed properly, and you will end up with the motor that costs you least over the years it spends turning.
