Energy Savings with IE1, IE2 & IE3 Motors

Energy savings with efficient motors — why it matters 

Motors power virtually every industry and commercial facility. Because motors typically account for the majority of industrial electricity use, improving motor efficiency is one of the fastest ways to cut energy bills, reduce carbon emissions and improve profitability.

Key facts:

• In many industries, motors account for ~70% of total electrical consumption.

• Over a motor’s lifetime, ~88% of total lifecycle cost is energy cost (purchase, maintenance and downtime account for the rest).
  → This makes efficiency improvements extremely cost-effective.

How premium/high-efficiency motors reduce losses

Extra-premium / high-efficiency motors achieve lower losses by:

1. Reducing stator copper losses — more active copper/optimized winding designs.

2. Reducing core (iron) losses — higher-grade silicon steel and better lamination.

3. Reducing friction & windage losses — improved fan and bearing design.

4. Better thermal design and materials → lower thermal and electrical stress, longer life.

Advantages of extra-premium motors vs IE2 / IE3

• Stable high efficiency from ~60%–100% load, yielding better real-world savings.

• Lower electricity consumption (direct bill savings).

• Better thermal and electrical stress resistance, enabling higher ambient operation.

• Less frequent rewind-related efficiency degradation (and better OEM support).

Indian standards overview:

• IS:12615 (1989) — initial energy-efficient motor standard (covers up to 37 kW, 4-pole).

• Revision I (2004) — extended to 0.37 kW–160 kW (2–4 pole) plus 6 & 8 pole ranges; introduced Eff1/Eff2 and IEC 60034-2 test methodology.

• Revision II (2011) — aligned with IEC 60034-30: introduced IE1/IE2/IE3 classes, extended motor range (0.37 kW–375 kW for 2/4/6 pole), and required test standard IS:15999 / IEC 60034-2-1; added parameters (breakaway torque, currents, etc.).

When should you replace motors? — Practical step-by-step

1. Build a motor database: nameplate details, rated efficiency, age, operating hours, location, duty cycle.

2. Record failures & rewinds: count of rewinds and repairs for each motor.

3. Compare OEM efficiency curves and document how rewinds affected efficiency (typical drop: 1%–5% per rewind).

4. Flag motors >8–10 years old for detailed review (higher chance of being inefficient).

5. If rewinding cost is high for small/medium motors (<50 kW), compare replacement vs repair.

6. Run a payback calculation: compare annual energy cost (using actual loading and hours) vs incremental purchase cost. Replace when payback is acceptable for your business.

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Worked example — 20 kW motor (practical cost-benefit)

Assumptions:

• Motor rated output = 20 kW

• Operating load = 80% → output in-service = 20 × 0.8 = 16 kW

• Annual run hours = 20 hr/day × 365 = 7,300 hr/year

• Electricity cost = ₹8.00 / kWh

Energy consumed (input kWh/year) = (output kW × hours) / efficiency
Annual cost = input kWh/year × ₹8.00

Efficiencies used:

• IE1 (Eff2) = 88.70% (0.887)

• IE2 = 90.60% (0.906)

• IE3 = 92.10% (0.921)

Calculated annual energy cost

Motor class	Efficiency	Input energy (kWh/year)	Annual energy cost (₹)
IE1	88.70%	131,679.82 kWh	₹1,053,438.56
IE2	90.60%	128,918.32 kWh	₹1,031,346.58
IE3	92.10%	126,818.68 kWh	₹1,014,549.40

Annual savings (rounded)

• IE1 → IE2 savings = ₹22,091.98 / year

• IE1 → IE3 savings = ₹38,889.16 / year

• IE2 → IE3 savings = ₹16,797.18 / year

Typical purchase prices (example)

• IE1: ₹45,000

• IE2: ₹55,000

• IE3: ₹63,000

Payback (months)

• IE1 → IE2: additional cost ₹10,000 → payback ≈ 5.43 months

• IE1 → IE3: additional cost ₹18,000 → payback ≈ 5.55 months

• IE2 → IE3: additional cost ₹8,000 → payback ≈ 5.72 months

Conclusion: With the assumptions above (heavy annual hours and ₹8/kWh), extra premium motors pay back within about 5–6 months — an excellent return on investment. (Adjust your inputs — run hours, energy price and actual motor efficiencies — to get plant-specific payback.)

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Practical checklist before replacement

• Confirm actual operating load profile (measure average % loading, not assumed).

• Verify actual run hours and seasonal usage.

• Check power tariff (energy charge, demand charge, time-of-day). Some savings affect demand charges too.

• Include downtime, maintenance and scheduled life in lifecycle cost.

• Validate OEM efficiency & warranty, and check service availability.

• If motor is critically sized and variable-load, consider VFD + premium motor for maximum savings and process control.

Quick recommendations

1. For motors with high run-hours (>3,000–4,000 hr/yr) and older than 8 years, strongly consider replacement with IE3 or premium motors.

2. For frequent rewinds or where rewinding costs approach new-motor price, prefer replacement.

3. Use the site-specific payback model — plug actual tariffs, hours, and measured loading to get precise ROI.

4. Combine motor replacement with operational measures (VFDs, power factor correction, scheduled maintenance) for extra savings.

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