Amps to Kilowatts Calculator
Convert electrical current (amps) to power (kilowatts) for AC and DC circuits
Power Conversion Formulas
Understanding Amps and Kilowatts
Amps (amperes) measure electrical current—the flow of electrons through a conductor. Kilowatts (kW) measure power—the rate of energy consumption or production. Converting between them requires knowing the voltage and, for AC circuits, the power factor.
For DC circuits, the calculation is straightforward: Power = Current × Voltage. For AC circuits, power factor (PF) accounts for the phase difference between voltage and current in inductive or capacitive loads like motors and transformers. Real-world AC loads rarely have a power factor of 1.0.
This calculator handles DC, single-phase AC, and three-phase AC circuits—covering everything from household appliances to industrial motors. It's essential for electricians, engineers, and anyone sizing electrical equipment, circuits, or generators.
Circuit Types Explained
DC (Direct Current)
Batteries, solar panels, electronics. Power = Amps × Volts. No power factor needed.
Single-Phase AC
Household outlets (120V/240V). Power = Amps × Volts × PF. Most home appliances.
Three-Phase AC
Industrial power. Power = √3 × Amps × Volts × PF. More efficient for heavy loads.
Power Factor
Ratio of real power to apparent power. Motors: 0.80-0.85. Resistive loads: 1.0.
Common Voltage and Power Factor Values
| Application | Voltage | Power Factor | Circuit Type |
|---|---|---|---|
| US Household | 120V | 0.95-1.0 | Single-Phase |
| US Large Appliances | 240V | 0.85-0.95 | Single-Phase |
| European Household | 230V | 0.95-1.0 | Single-Phase |
| Industrial Motors | 480V | 0.80-0.85 | Three-Phase |
| EV Charging (L2) | 240V | 0.95+ | Single-Phase |
| Solar Inverters | 240V | 0.99+ | Single-Phase |
Practical Applications
Circuit Sizing
A 15-amp, 120V circuit provides 1.8 kW max. A 20-amp circuit provides 2.4 kW. Use 80% rule for continuous loads.
Generator Sizing
Total your loads in kW, add 20% margin, then select generator kVA rating (kVA = kW ÷ PF).
EV Charging
Level 2 chargers at 40 amps, 240V deliver 9.6 kW. A 10 kWh battery needs about 1 hour to charge.
Industrial Motors
A 10 HP motor draws about 15 amps at 480V three-phase. Use nameplate data for accuracy.
Frequently Asked Questions
What is power factor and why does it matter?
Power factor (PF) is the ratio between real power (kW) and apparent power (kVA). It ranges from 0 to 1. Inductive loads like motors have PF < 1, meaning they draw more current than purely resistive loads for the same power. Low PF wastes energy and requires larger wiring.
How do I find the power factor of my device?
Check the nameplate or specifications. For motors, it's typically 0.80-0.90. For resistive heaters, it's 1.0. For LED lighting with drivers, it's usually 0.90+. If unknown, 0.85 is a reasonable estimate for mixed loads.
What's the difference between kW and kVA?
kW (kilowatts) is real power—what does useful work. kVA (kilovolt-amperes) is apparent power—the total current × voltage. For DC and resistive AC loads, they're equal. For inductive/capacitive AC loads: kW = kVA × PF. Generators are rated in kVA.
Why is three-phase power more efficient?
Three-phase delivers constant power (single-phase pulsates), uses less copper for the same power (3 wires vs. 2), and runs motors more smoothly. Industrial facilities use three-phase for heavy loads because it's more efficient and cost-effective.
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