One of the most critical decision points you face when buying a new electric motor is the efficiency class: IE3 or IE4? At first glance, the one-and-a-half percentage point difference in efficiency between the two classes may seem trivial; yet on a motor that runs 16 hours a day, that gap can turn into energy savings large enough to pay back the purchase price of the motor within a few years. By the same token, in a low-runtime application the premium paid for IE4 may never amortise itself. In other words, the right answer is not the same for every business; it depends on operating hours, load factor and your electricity unit price.

As HEM Motor — a company that has been manufacturing electric motors since 1979 and delivers quickly to businesses across Turkey thanks to a strong stock structure — in this article we explain the technical differences between the IE3 and IE4 classes in plain language, work through a step-by-step payback calculation using a real 22 kW motor example, and set out with concrete criteria which class is the more sensible investment in which scenario. By the end of the article, you will be able to plug in your own figures and run your own calculation within minutes.

What Are IE Efficiency Classes and Why Do They Matter So Much?

IE (International Efficiency) classes form an international system that rates the efficiency of electric motors according to the IEC 60034-30-1 standard. IE1 denotes standard efficiency, IE2 high efficiency, IE3 premium efficiency and IE4 super premium efficiency. As the class rises, a larger share of the electricity the motor draws from the grid is transferred to the shaft as mechanical power, while a smaller share is lost as heat.

The reason this subject matters so much is simple: more than roughly 95 percent of an electric motor's lifetime cost comes from the electricity it consumes. The purchase price and maintenance expenses are only a small slice of the total cost of ownership. Therefore, looking only at the price tag when choosing a motor means looking only at the visible tip of the iceberg. Because the electric motors used in industry account for the single largest item of total electricity consumption in most facilities, the choice of efficiency class is a strategic decision that directly affects business profitability.

IE3 Premium Efficiency Class

IE3 is a proven class that has become the legal minimum efficiency level for many power ranges in Turkey and Europe today. For example, on a 22 kW, 4-pole asynchronous motor, the nominal efficiency required by the IE3 class is around 93.0 percent. IE3 motors are available with a wide range of power and frame options in the classic IE3 electric motors category; in terms of the price-efficiency balance, they are the reliable standard for many applications. The asynchronous electric motors in HEM Motor's production programme, with their broad power range from 0.55 kW up to 355 kW, IP55 protection class and class F insulation, are typical examples of this segment.

IE4 Super Premium Efficiency Class

IE4 is the highest efficiency step of current series production technology. In the same 22 kW, 4-pole motor example, the IE4 class offers a nominal efficiency of around 94.5 percent and above. This efficiency increase is achieved through higher-grade silicon steel lamination packs, windings with a higher copper fill factor, optimised rotor geometry and more precise workmanship. Naturally, the production cost and purchase price of an IE4 motor are somewhat higher than those of IE3; however, at high operating hours this difference is recovered surprisingly quickly, as we will demonstrate below. HEM Motor's IE4 high-efficiency electric motors, with their cast iron body construction and drive-compatible design, have been developed for continuously running lines.

IE3 ve IE4 elektrik motoru verimlilik sınıfları karşılaştırması

Payback Calculation: A Step-by-Step Comparison on a 22 kW Motor

Let us set the theory aside and work through a real scenario. Suppose we are choosing a 22 kW fan motor in a two-shift production facility that runs 16 hours a day, 300 days a year, close to full load. Let the two options we will compare be as follows:

  • Option A — IE3: Nominal efficiency 93.0%
  • Option B — IE4: Nominal efficiency 94.5%

Step 1: Calculate the Power Drawn from the Grid

The power on the motor nameplate is the mechanical power taken from the shaft. The electrical power drawn from the grid is found by dividing the shaft power by the efficiency:

Drawn power = Shaft power ÷ Efficiency

  • IE3 motor: 22 ÷ 0.930 = 23.66 kW
  • IE4 motor: 22 ÷ 0.945 = 23.28 kW

The difference looks small at first glance: only 0.38 kW. But this difference is the extra power drawn from the grid every hour the motor runs, and once the hours start to accumulate the picture changes.

Step 2: Find the Annual Operating Hours and the kWh Difference

Annual operating time: 16 hours × 300 days = 4,800 hours.

Annual consumption difference = (P ÷ ηIE3 − P ÷ ηIE4) × annual hours

Let us plug in the numbers: (23.66 − 23.28) × 4,800 = 0.38 × 4,800 ≈ 1,805 kWh/year.

So between two motors doing the same job, a consumption difference of roughly 1,805 kWh per year arises purely from the difference in efficiency class. This is a saving that repeats every year throughout the entire economic life of the motor (usually 15-20 years).

Step 3: Turn the Saving into Money and the Price Difference into a Payback Period

Because electricity unit prices vary according to your contract and tariff, instead of writing a fixed amount here we give you the formula; you only need to insert the unit price from your own bill:

Annual saving = 1,805 kWh × your electricity unit price (per kWh)

Payback period (years) = (IE4 price − IE3 price) ÷ annual saving

For example, if you take your electricity unit price as X per kWh, your annual saving becomes 1,805 × X. When you divide the purchase price difference between IE3 and IE4 by this amount, you obtain the payback period in years. In practice, you will see that in applications running two shifts and above this period usually corresponds to a very small fraction of the motor's economic life, whereas in single-shift and intermittent operation it lengthens noticeably. The beauty of the calculation is this: it works entirely with your own data and leaves no room for debate over the result.

And do not forget the scale effect: this calculation is for a single motor. If a medium-sized facility has ten motors running on a similar profile, the annual difference exceeds 18,000 kWh; in a fleet of fifty motors the figure reaches the level of 90,000 kWh. Businesses that evaluate the efficiency class decision not on a single-motor basis but across the entire motor fleet close the same calculation with far larger saving figures.

22 kW elektrik motoru amortisman ve enerji tasarrufu hesabı

The Hidden Cost of Carrying On with the Wrong or Old Motor

There is also a flip side to this calculation: the cost of not deciding and carrying on with an old, low-efficiency motor. The real efficiency of an IE1 or IE2 class motor — especially one whose winding has been renewed over the years — may have dropped even below its nameplate value; every rewind operation can shave one to two points off the efficiency. An old 22 kW motor running at 89 percent efficiency consumes thousands of extra kWh per year compared with the IE4 example above. This difference does not appear as a separate line on your bill; it quietly dissolves into the general electricity expense and is paid unnoticed for years.

Moreover, the issue is not only energy. The increased failure risk in old motors, unplanned downtime, emergency service and the scramble to find a spare all come back as lost production. The cost of a single shift of unplanned downtime is often higher than the price difference of a new motor. We examined this subject in detail, in all its dimensions and with a real consumption calculation and payback period, in our article on what replacing your old motor with IE4 gains you.

In Which Cases Is IE3 Sufficient?

It would not be an honest sales approach to claim that IE4 is always and everywhere the only right answer. In the scenarios below, IE3 is the sensible choice that does the job reliably without straining your budget:

  • Low operating hours: If the motor runs only a few hours a day or only seasonally (for example a backup pump, a door mechanism, a rarely used conveyor), the annual kWh difference stays small and the IE4 premium does not come back within a reasonable period.
  • Short project life: If the facility or line is planned to be relocated, converted or shut down within a few years, pricing in long-term savings becomes meaningless.
  • Low loading: If the motor is constantly loaded far below its nominal power, the absolute loss difference also shrinks; making the right power selection first gains you more than the efficiency class.
  • Budget-priority renewal projects: Upgrading more old motors to IE3 with the same budget can sometimes deliver more total energy saving than making a single motor IE4.

In Which Cases Is IE4 a Sensible Investment?

  • High operating hours: Fans, pumps, compressors and conveyors running two or three shifts are the natural home of IE4. In every application above 4,000 hours a year the calculation quickly turns in favour of IE4.
  • High load factor: On motors loaded close to their nominal power, the efficiency difference is fully realised.
  • Energy-intensive facilities: If electricity expense accounts for a high share of total cost, every efficiency point in the motor fleet feeds directly into competitiveness.
  • Sustainability and reporting targets: In businesses with a commitment to reduce their carbon footprint, applying an ISO 50001 energy management system or presenting emission reports to their customers, IE4 makes a measurable contribution to the targets.
  • New investments: On a line built from scratch there is no dismantling, installation or downtime cost of changing the motor later; the only difference is the purchase price difference, and this is the most advantageous scenario for IE4.

Sanayi tesisinde yüksek verimli elektrik motoru uygulaması

Other Technical Points to Watch When Deciding

The efficiency class alone is not a sufficient criterion; for the right motor investment, add the following points to your purchasing specification as well:

  • Protection class: For dusty and humid industrial environments, IP55 protection class is the minimum assurance.
  • Insulation class: Class F insulation guarantees the windings' resistance to high temperatures and a long service life.
  • Body material: A cast iron body is the standard for demanding industrial conditions in terms of vibration damping, mechanical strength and heat dissipation.
  • Drive compatibility: On motors to be used with a frequency converter, make sure the winding insulation is suitable for the drive pulses.
  • Correct power selection: An oversized motor runs underloaded and loses its efficiency advantage; get manufacturer support for power selection according to your load profile.

If you would like to reach a wide product range that meets all these criteria from a single point, you can review all power options from 0.55 kW up to 355 kW in our high-efficiency electric motors category.

Why Should You Buy from HEM Motor?

Manufacturing electric motors since 1979, HEM Motor removes all the intermediate links with its dual identity as both manufacturer and seller. This brings you three concrete benefits. First, because you buy from the manufacturer, your technical questions receive an engineer's answer rather than a salesperson's; your motor is validated against your application. Second, thanks to our strong stock structure in Turkey, waiting for standard powers is next to nil; with fast delivery we minimise your downtime risk. Third, because we keep both the IE3 and IE4 classes in our own production programme, we do not push a single class on you; we recommend whichever class the calculation points to. If you are considering renewing several motors at once or standardising your fleet, our guide on the ways to reduce cost in wholesale purchasing will guide your buying process.

Frequently Asked Questions

How long does it take for the IE4 motor's price difference to amortise itself?

This depends entirely on your operating hours, your load factor and your electricity unit price. Using the formula above with your own data, you can find the clear result within minutes: multiply the annual kWh difference by your unit price and divide the purchase price difference by this amount. As a general rule, on motors running 4,000 hours a year and above the payback period is short and turns into net gain over the life of the motor; at low operating hours, IE3 is usually the more sensible choice. At the quotation stage we run this calculation together for your application.

Can an IE4 motor be fitted directly in place of my existing IE2 motor?

In most cases, yes. Because IE3 and IE4 motors are produced in standard IEC frame dimensions, within the same frame size the shaft height, flange and mounting dimensions are preserved. In some power ratings a frame size larger may be required due to the efficiency increase; for this reason it is enough to send us the nameplate details and mounting type of your existing motor before ordering. Our technical team confirms the correct model for a like-for-like replacement.

What is your delivery time from stock, and what should I do in an urgent need?

In standard power and frame types, our IE3 and IE4 motors wait ready in our stocks in Turkey; for items in stock, shipment is scheduled for the same or the next day. If your line has stopped due to a failure, once you send a photo of the motor nameplate we quickly identify the suitable model and offer the shortest delivery option. For custom designs and high-power groups, a delivery date is committed to you once the production plan is finalised.

Get a Quote

The answer to the IE3-or-IE4 question is hidden in your business's numbers; and we love talking in those numbers. Send us your motor's power, its daily operating hours and your application; let us run your payback calculation together, report the stock status instantly and prepare a quote tailored to you the same day. You can reach us on +90 (532) 345 49 86 or send your request via our contact us page. Invest in the right motor with the right calculation, with the assurance of HEM Motor.