IE efficiency classes (IE1–IE5) classify the minimum efficiency of three-phase motors according to IEC 60034-30-1. The class determines what proportion of the supplied electrical power is available as mechanical shaft power.
Why IE classes are crucial
Anyone who buys an electric motor looks first at the purchase price. This is understandable - but economically short-sighted. For a typical industrial motor with 11 kW that runs for 6,000 operating hours per year, only 2-4% of the total costs over a 15-year service life are attributable to purchase and maintenance. The rest - over 95% - are electricity costs.
This is precisely where the IE efficiency classes come in. They quantify how much of the supplied electrical power is actually available as mechanical shaft power - and how much is lost as heat. The difference between IE1 and IE3 for an 11 kW motor is around 3.8 percentage points of efficiency. That doesn't sound like much, but at 6,000 h/a and €0.18/kWh, it adds up to over €1,000 in additional costs per year.
Key takeaway:
For an average industrial motor, life cycle electricity costs exceed the purchase price by a factor of 20–50. The IE class is therefore not a certification formality, but the most important economic indicator when selecting a motor.
What are IE classes?
IE stands for International Efficiency. The classification is defined in the international standard IEC 60034-30-1:2014 (Rotating electrical machines - Part 30-1). It specifies the minimum efficiency that a three-phase asynchronous motor must have at rated load, rated voltage and rated frequency in order to belong to a class. The scope covers two- to eight-pole squirrel cage asynchronous motors from 0.12 kW to 1,000 kW for 50 and 60 Hz.
Measurement methods: Direct vs. loss analysis
IEC 60034-30-1 refers to the measurement methods according to IEC 60034-2-1. Two approaches are relevant in practice:
- Direct method (Method A): Input and output power are measured simultaneously. Simple and fast, but at high efficiencies (>93%), the measuring accuracy becomes critical — even 0.5% measurement errors at the input or output significantly distort the result.
- Loss analysis (Method B/C): The individual loss components (copper losses, iron losses, friction losses, stray losses) are measured separately and added together. More complex, but the preferred method for verifiable type tests for IE3 and above.
- Error correction (Method H): Modified version with statistical correction of additional losses. Used in the EU as a reference method for declarations of conformity.
Important: The η value on the nameplate is the guaranteed efficiency of this motor type at rated operation – not the minimum of a specific IE class. An IE3 motor can and should exceed the class minimum.
IE1–IE5: Efficiency levels in comparison
The following table shows the minimum efficiencies according to IEC 60034-30-1:2014 for 4-pole squirrel cage motors at 50 Hz and three practically relevant power classes:
| IE class | Designation | 4 kW | 11 kW | 75 kW | EU status 2026 |
|---|---|---|---|---|---|
| IE1 | Standard Efficiency | 82.5 % | 87.6 % | 93.0 % | No longer marketable in the EU |
| IE2 | High Efficiency | 86.6 % | 89.8 % | 94.0 % | Minimum requirement below 0.75 kW; no longer permitted from 0.75 kW |
| IE3 | Premium Efficiency | 88.6 % | 91.4 % | 95.0 % | Mandatory 0.75–1,000 kW (since 07/2021) |
| IE4 | Super-Premium Efficiency | 91.1 % | 93.3 % | 96.0 % | Mandatory 75–200 kW (since 07/2023) |
| IE5 | Ultra-Premium Efficiency | 91.7 % | 95.0 % | 97.8 % | No EU obligation; voluntary (PMSM) |
Minimum efficiencies for 4-pole squirrel cage asynchronous motors, 50 Hz, at 100 % rated load. Sources: IE2–IE4 per Regulation (EU) 2019/1781, Annex I, Tables 1–3 (identical wording to IEC 60034-30-1:2014); IE1 per IEC 60034-30-1:2014; IE5 per IEC/TS 60034-30-2.
Practical note: The efficiency difference between two IE classes is only 1–2 percentage points for the same motor. For large motors (>75 kW) with long running times, however, this means thousands of euros in additional annual energy costs – which is why falling short of the standard is generally not tolerable.
EU Regulation 2019/1781 (Ecodesign): Obligations and exemptions
The EU Regulation 2019/1781 (Ecodesign Regulation for Electric Motors) regulates which motors may be placed on the market in the EU. It applies to manufacturers and importers – not to end users who operate existing machines.
Gradual introduction
| Date | Requirement | Power range |
|---|---|---|
| 01.07.2021 | At least IE3 | 0.75–1,000 kW, 2–8-pole (excluding Ex eb motors) |
| 01.07.2021 | At least IE2 | 0.12 kW to below 0.75 kW, 2–8-pole |
| 01.07.2023 | At least IE2 | Ex eb motors 0.12–1,000 kW and single-phase motors from 0.12 kW |
| 01.07.2023 | At least IE4 | 75–200 kW, 2–6-pole (excluding brake and explosion-protected motors) |
Exceptions (as of 2026)
The following motor types are exempt from the IE3/IE4 obligations:
- Ex motors: Ex eb increased-safety motors are exempt from the IE3 requirement, but have had to reach at least IE2 since 1 July 2023 (0.12–1,000 kW). Only explosion-protected motors for underground installations are fully exempt. Explosion-protected motors are exempt from the IE4 requirement (75–200 kW).
- Brake motors: Motors with integrated electromagnetic brake where the brake cannot be certified separately from the motor.
- Fully integrated motors: Motors that cannot be removed from the product and tested separately due to their design (e.g. spindle motors in machine tools). Regulated separately: motors submerged in liquid (e.g. submersible pumps).
- Single-phase motors: Exempt from the IE3 requirement, but from 0.12 kW they have had to reach at least IE2 since 1 July 2023.
- Motors with more than 8 poles: Outside the scope of the regulation (Art. 2(1)(a)(i)).
- Motors not rated for continuous duty: The regulation only covers motors rated for continuous duty (S1, S3 ≥ 80% or S6 ≥ 80%, Art. 3); pure S2 motors or S3 with a lower duty cycle are not covered.
- Export to third countries: The regulation only applies to the EU internal market; the regulations of the destination country apply to exports.
Important for replacement purchases: The regulation applies when motors are placed on the market - i.e. when newly manufactured motors are purchased. The continued operation of an already installed IE1 or IE2 motor in an existing system is not prohibited. However, the obligation applies in full to new investments and the replacement of defective motors.
When is IE4 worthwhile? - Sample TCO calculation
The following worked example shows how much energy and energy costs IE4 saves compared with IE3. The parameters correspond to a typical medium-sized industrial drive:
- Rated power11 kW
- Operating hours6,000 h/year
- Electricity price0.18 €/kWh (industrial tariff)
- Useful life15 years
- Utilization100 % rated load (conservative assumption)
Calculation of the input power
IE3 (η = 91.4 %):
Pein = 11 kW / 0.914 = 12.04 kW
Annual energy = 11 / 0.914 × 6,000 ≈ 72,210 kWh
Annual costs = 72,210 × 0.18 ≈ 12,998 €
IE4 (η = 93.3 %):
Pein = 11 kW / 0.933 = 11.79 kW
Annual energy = 11 / 0.933 × 6,000 ≈ 70,740 kWh
Annual costs = 70,740 × 0.18 = 12,733 €
Result
The price premium of an IE4 motor pays back faster the more hours per year it runs; the exact calculation depends on the actual premium and the electricity price. At high operating hours, IE4 is usually the more economical choice.
With electricity price increases or longer operating times, the economic case for IE4 improves further. The example is deliberately conservative: it assumes constant full load and no partial-load phases. In practice, the relative advantage of IE4 is greatest at rated load; a VFD should be considered instead for frequent partial-load operation. IE3 and IE4 asynchronous motors in IEC frame sizes are available in the TEA asynchronous motors range. For a complete drivetrain assessment, see the guide on TCO calculation for drive trains.
CO₂ balance: How much emission does IE4 save?
The energy savings of a higher IE class can be expressed not only in euros, but also in avoided CO₂ emissions — an increasingly relevant factor for sustainability reports (e.g. under the CSRD) and for assessing Scope 2 emissions. The decisive figure is the emission factor of the electricity mix, by which the additional or reduced annual electricity consumption is multiplied.
m(CO₂) = Wel × EFelectricity
Here Wel is the annual electrical energy in kWh and EFelectricity the emission factor in kg CO₂/kWh. For the German electricity mix, the Federal Environment Agency (UBA) reports approximately 0.344 kg CO₂/kWh for the 2025 electricity mix (the figure "specific emissions of the electricity mix"). We use the same 11 kW drive as in the TCO calculation (6,000 h/a, 100 % rated load):
IE3 (η = 91.4 %), Wel = 72,210 kWh/a:
m(CO₂) = 72,210 × 0.344 = 24,840 kg/a ≈ 24.8 t/a
IE4 (η = 93.3 %), Wel = 70,740 kWh/a:
m(CO₂) = 70,740 × 0.344 ≈ 24,335 kg/a ≈ 24.3 t/a
Δm(CO₂) = 1,470 kWh × 0.344 ≈ 506 kg/a → × 15 a ≈ 7,590 kg ≈ 7.6 t
A single 11 kW motor therefore saves around 0.51 t CO₂ per year by switching from IE3 to IE4. Across a machine fleet of 50 comparable drives, this adds up to roughly 25.3 t CO₂/year. Buyers of grid electricity do not incur their own CO₂ certificate costs: power generation falls under the EU Emissions Trading System, whose carbon costs are already built into the electricity price and are therefore already included in the energy savings above. The CO₂ reduction mainly matters for greenhouse gas accounting (Scope 2) and sustainability reporting.
Validity note: The emission factor of the German electricity mix falls year on year as the share of renewable energy increases (in 2010 it was still above 0.55 kg/kWh). Anyone sourcing their own green electricity or a site PPA must use a significantly lower site-specific factor. The calculation above is therefore a conservative order of magnitude, not a fixed accounting value.
Part-load efficiency in figures: ASM vs. PMSM
The IE class according to IEC 60034-30-1 is determined exclusively at 100 % rated load. In practice, however, many drives operate permanently in the part-load range — fans and pumps with a quadratic load profile often at 40–70 %. This is precisely where real energy consumption is decided, and precisely where asynchronous (ASM) and permanent magnet synchronous motors (PMSM) behave markedly differently.
The following table shows typical efficiency curves of an 11 kW 4-pole motor across the load range. These are representative orders of magnitude from manufacturer performance maps — the standard does not define minimum values for part load; only the data sheet of the specific motor is binding.
| Load (% PN) | ASM IE3 | ASM IE4 | PMSM IE4 |
|---|---|---|---|
| 100 % | 91.4 % | 93.3 % | 93.5 % |
| 75 % | 91.6 % | 92.8 % | 93.2 % |
| 50 % | 90.3 % | 91.8 % | 92.6 % |
| 25 % | 85.5 % | 87.8 % | 90.5 % |
Representative manufacturer performance-map values for an 11 kW 4-pole motor; not standard values. IEC 60034-30-1 specifies exclusively the value at 100 % rated load.
Two patterns can be read off: First, the asynchronous motor reaches its efficiency peak not at 100 % but slightly below (typically 70–80 % load), because load-independent iron and friction losses only "dilute" relatively as rated load is approached. Second, the ASM curve drops off markedly more steeply at 25 % load than the PMSM (see table above), which — thanks to the absence of rotor slip losses — shows a noticeably flatter curve. This is why PMSMs tend to lead energetically in permanent low-load operation.
Practical consequence: If the real operating point lies predominantly below 50 % rated load, the IE class alone says little about the actual annual consumption. In that case, a load-weighted efficiency over the load spectrum is more meaningful than the rated-load η — and a speed-controlled variable-frequency drive usually delivers more than a jump to the next-higher IE class. A frequent additional consequence is an oversized motor that runs permanently in the unfavourable part-load region; correctly dimensioning for the real operating point is the simplest efficiency measure.
Permanent magnet synchronous motor (PMSM) vs. asynchronous motor with IE4/IE5
IE4 can be realized in different technological ways: through optimized asynchronous motors (ASM) with an improved laminated core and copper rod cage rotor or through permanent magnet synchronous motors (PMSM). IE5 practically always requires PMSM technology. The choice between the two approaches has far-reaching system implications:
| Feature | PMSM (IE4/IE5) | ASM (IE3/IE4) |
|---|---|---|
| Direct start on the grid | Not possible – VFD mandatory | Possible (direct or star-delta start) |
| Efficiency at rated load | Higher (no slip, no rotor losses) | Slightly lower (slip ~2–4 %) |
| Efficiency at partial load | Significantly better - flatter curve | Stronger drop under 50 % load |
| Physical size | More compact at equal power rating | Larger, heavier |
| Acquisition costs | Higher (motor + VFD mandatory) | Lower; VFD optional |
| Overload capacity | Limited (risk of demagnetization) | High (150–200 % rated torque for short periods) |
| Maintenance / replacement | Proprietary VFD required; magnets are non-repairable | Standardized; wide availability |
| Recycling | Rare earths in magnets difficult to recycle | Iron and copper easily recyclable |
Recommendation: IE4 ASM motors are the safe choice for classic industrial drives with direct start or an optional VFD. PMSMs are worthwhile for continuous operation, variable loads and when an inverter is already present in the system — typically for pumps, fans and servo systems. How the load profile influences motor selection is explained in the guide on motor selection by load profile.
Selection matrix: IE class by application
The optimum IE class depends not only on the efficiency, but also on the operating profile, the load characteristics and the system boundary conditions. The following matrix provides a practical decision-making aid:
| Use case | Recommended IE class | Reason |
|---|---|---|
| Pump with constant load profile (> 4,000 h/a) | IE4 | Long running times at rated load — premium pays back quickly |
| Fan / pump with variable load profile + VFD | IE3 + VFD | Speed control by VFD saves more than a higher IE class; quadratic load profile |
| Servo axis / highly dynamic positioning | IE4/IE5 PMSM | VFD available anyway; compactness and partial load efficiency decisive |
| Brake motor (hoist / conveyor drive) | IE2/IE3 (ASM) | Exception to ecodesign; PMSM not suitable due to overload and brake integration |
| Short-term operation / infrequent use (< 500 h/a) | IE3 (mandatory) | Statutory minimum IE3; higher classes do not pay back at low running hours |
| Compressor / grinder ≥ 75 kW (> 5,000 h/a) | IE4 (mandatory) | Required by law since 07/2023; payback independent of operating hours |
Common pitfalls in practice
1. IE class and VFD
A common misconception: "My VFD makes the motor more efficient, so I don't need a high IE class." This is not correct. The VFD improves system efficiency by adjusting speed — but it does not change the motor's efficiency at a given speed and load. An IE2 motor on a VFD still has lower efficiency at rated operating conditions. The exception: if the VFD runs permanently well below rated load, speed control can overcompensate for the IE class difference.
2. Efficiency at partial load not classified
IEC 60034-30-1 defines IE classes exclusively at 100 % rated load. Partial-load behavior — more relevant than rated load for many applications — is not part of the classification. Asynchronous motors lose efficiency disproportionately below 50 % load; PMSM motors show a flatter partial-load curve. To optimize energy efficiency in the partial-load range, request the manufacturer's partial-load performance curve and combine it with the VFD system efficiency.
3. Secondary standards and system efficiency
In addition to IEC 60034-30-1, there are other relevant standards:
- IEC 60034-30-2: Extended efficiency classes for variable speed motors (IE classes with VFD) - defines IE classes at system level (motor + VFD).
- EN 50598-2: System efficiency classes for VFD motor systems (IES0-IES2) - enables the comparison of overall drive systems regardless of the individual component efficiency.
- IEC 60034-2-1: Test methods - decisive for whether the declared η-value is reliable. Pay attention to certified test reports according to Method H.
- NEMA MG1: US counterpart to IEC; the relevant standard for imports from North America (efficiency classes NEMA Nom. Eff. / NEMA Premium).
Practical Tip from TEA: Don't just ask for the IE class - ask the motor supplier for the guaranteed η value at your actual operating point (load and number of poles) plus the test report according to Method H (IEC 60034-2-1): direct measurement becomes inaccurate above 93 % efficiency, and an IE3 motor with η = 93.5 % beats an IE4 motor that only just reaches the class limit of 93.3 %. In our consulting work we see two recurring procurement errors: the IE class is confused with the part-load efficiency (the standard applies only at 100 % rated load), and where a variable-frequency drive is planned anyway, an expensive IE5 PMSM is chosen where an IE3 induction motor + VFD is already sufficient in terms of energy. For imports from North America there is an additional pitfall: a “NEMA Premium” motor does not automatically correspond to IE3 - the η values according to NEMA MG1 must be checked separately against the IEC class limits.
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