Electric Motor Full Load Amps (FLA) & Running Cost Calculator
Calculate 1-phase and 3-phase motor current draw (FLA), kVA, breaker sizing, and hourly/annual power bills.
Last reviewed by the myCalculator Editorial Team
Input Parameters
e.g. 11 kW (15 HP) motor
Typical AC induction motor power factor ranges between 0.82 and 0.89
IE3 Premium Efficiency ~91-94%, IE2 High Efficiency ~88-90%
Calculation Results
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Formula & How Electric Motor Full Load Amps (FLA) & Running Cost Calculator Works
Full load amps is the current a motor draws at its rated output. For a three-phase motor it is FLA = P ÷ (√3 × V × PF × η). An 11 kW motor on 415 V with a power factor of 0.86 and an efficiency of 91.2% draws 11,000 ÷ (1.732 × 415 × 0.86 × 0.912) = about 19.5 A. Cable and protection are commonly sized at 125% of FLA, which here is about 24.4 A, though the starting current is much higher and the installation rules require a proper design. Use the motor's nameplate current if you have it. A licensed electrician must select cables, protective devices and starters for any installation.
- Enter Electrical Supply Phase: Input your target parameter value.
- Enter Motor Mechanical Output Power (kW) (kW): Input your target parameter value.
- Enter Supply Voltage (V) (Volts): Input your target parameter value.
- Enter Operating Power Factor (cos φ): Input your target parameter value.
- Enter Motor Efficiency Class (%) (%): Input your target parameter value.
- Enter Daily Operating Hours (hrs/day): Input your target parameter value.
- Enter Electricity Tariff (¢/kWh) (¢/kWh): Input your target parameter value.
- Apply Formula: Calculate using
3-Phase FLA = P_mech ÷ (√3 × V × PF × η) | 1-Phase FLA = P_mech ÷ (V × PF × η) | Cable/Breaker = FLA × 1.25. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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MyCalculator.com.au. (2026). Electric Motor Full Load Amps (FLA) & Running Cost Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/engineering/motor-full-load-amps
MyCalculator.com.au. (2026) 'Electric Motor Full Load Amps (FLA) & Running Cost Calculator'. Available at: https://www.mycalculator.com.au/calculators/engineering/motor-full-load-amps (Accessed: 24 October 2026).
Frequently Asked Questions (FAQs)
Why is motor efficiency and power factor critical when calculating FLA?
Because electric motors do not convert 100% of electrical energy into mechanical work (efficiency loss) and draw reactive magnetising current (power factor loss), the actual electrical input current drawn from the grid is significantly higher than theoretical mechanical power.
How do you size the circuit breaker and cable for a 3-phase motor?
Under Australian Standard AS/NZS 3000, continuous motor supply conductors must have a current-carrying capacity of at least 125% of the motor FLA to avoid thermal tripping under prolonged full-load operation.
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
Australian Standards including AS/NZS 3000 (Wiring Rules), AS 3600 (Concrete Structures), and AS 4100 (Steel Structures).
Accreditation and technical guidelines for civil, structural, mechanical, and electrical engineering.
Dedicated Australian home loans, borrowing capacity, mortgage repayments & refinance modeling.