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Single-Phase • Watts • Power

Calculate Power for Single-Phase

Calculate power from voltage, current and power factor cos φ.

Calculation Values

Note: This calculation is a technically sound simplification typical of online calculators. For practical sizing, standards, installation method, temperature, grouping, protective devices, cable type and manufacturer specifications must also be checked.

Formula Used

P = U × I × cos φ

P is the real power in watts, U the voltage in volts, I the current in amps and cos φ the power factor.

FAQ

Frequently Asked Questions about Calculate Power for Single-Phase

Briefly explained: formula, use case and key limits of the calculation.

Which formula applies to single-phase power? +

For real power on a single-phase system, P = U × I × cos φ applies.

What is real power? +

Real power is the power actually usable, converted into heat, motion or light.

Why is cos φ needed? +

cos φ accounts for the difference between real power and apparent power.

When can the calculation be done without cos φ? +

For purely resistive loads, cos φ = 1 can be used.

Practical guidance

Calculate active power for a single-phase load

Current, voltage and power factor determine electrical active power when amperes and volts are known.

Input values explained

Current
Enter the expected operating current, not a fuse rating. Motors and electronic power supplies may draw much higher starting or peak currents.
Voltage
Enter the voltage between line and neutral. This is commonly 230 V in low-voltage systems.
Power factor cos φ
cos φ is the ratio of active to apparent power. It is close to 1 for resistive heating loads; use the data-sheet value for motors and transformers.

Example: 16 A at 230 V

A load draws 16 A at 230 V with cos φ 0.90.

P = 230 V × 16 A × 0.90 = 3,312 W

Active power is about 3.31 kW, while apparent power is 3.68 kVA.

Distinguish watts from volt-amperes

Watts describe active power; VA describe apparent power. Conductors are loaded by current even when active power is lower.

Calculation limits

  • The model assumes sinusoidal quantities and a known power factor.
  • Efficiency and useful equipment output are not calculated.