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Electrical Power Calculator

Calculate real power (W/kW), apparent power (VA/kVA), and reactive power (VAR) for DC, single-phase, and 3-phase AC systems.

1. Enter your numbers  →  2. Check the answer  →  3. Read the steps before you trust it

V
A
ratio (0-1)

Typical values: 1.0 (resistive heater/lights), 0.80 - 0.92 (motors, compressors)

Calculated Electrical Power

Real / Active Power (P)
2.07 kW (2,070 W)

Working energy converted into heat, mechanical, or light work

Apparent Power (S)
2.3 kVA
Reactive Power (Q)
1.0025 kVAR
Equivalent Horsepower
2.7759HP

Step-by-Step Engineering Calculation

  1. 1Real Power: P=V×I×PF=230 V×10 A×0.9=2070.00 WP = V \times I \times \text{PF} = 230\text{ V} \times 10\text{ A} \times 0.9 = \mathbf{2070.00\text{ W}}
  2. 2Apparent Power: S=V×I=230 V×10 A=2300.00 VAS = V \times I = 230\text{ V} \times 10\text{ A} = \mathbf{2300.00\text{ VA}}
  3. 3Reactive Power: Q=S2−P2=(2300.00)2−(2070.00)2=1002.55 VARQ = \sqrt{S^2 - P^2} = \sqrt{(2300.00)^2 - (2070.00)^2} = \mathbf{1002.55\text{ VAR}}

Formula & Theory

P_DC = V × I | P_1φ = V × I × PF | P_3φ = √3 × V × I × PF

Electrical power is the rate at which electrical energy is transferred by an electric circuit.

Variable Definitions
P:
Real Power (Watts (W) / kW) – Useful energy doing mechanical, thermal, or computing work
S:
Apparent Power (Volt-Amperes (VA) / kVA) – Total vector sum of real and reactive power
Q:
Reactive Power (Volt-Amperes Reactive (VAR)) – Power stored and returned by inductive/capacitive fields
PF:
Power Factor (Ratio (0 - 1.0)) – Ratio of real power to apparent power (cos θ)

Worked Engineering Example

Three-Phase 400V Industrial Motor

A 400V 3-phase motor draws 25A with a power factor of 0.85.

Inputs:
  • Voltage: 400 V
  • Current: 25 A
  • Power Factor: 0.85
  • System: 3-Phase AC
Result: Real Power = 14.72 kW, Apparent Power = 17.32 kVA

Key Assumptions

  • •Balanced 3-phase loads with sinusoidal voltage waveforms.

Limitations & Safety Scope

  • •Harmonic distortion from non-linear VFDs or switching power supplies can lower the true power factor.

Frequently Asked Questions

What is the difference between Watts and VA?

Watts (W) measures real power consumed and transformed into work or heat, while Volt-Amperes (VA) measures total apparent power supplied to the circuit.

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Educational & Reference Notice: This calculator provides technical estimates based on standard physical formulas. Actual electrical installation, protective device sizing, and conductor selection must be verified against the applicable electrical code (NEC, IEC, CEC) by a licensed electrician or qualified professional engineer.