Physics

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Generator Power Calculator.

Calculate apparent, real input, and real output power from an explicit phase model, voltage, current, power factor, and efficiency.

On-device calculationNo signup
01

Set your values

Results update as you type.

Apparent power: 2,300 VA

Apparent power

0.000000VA
Apparent power (kVA): 2.3 kVA

Apparent power (kVA)

0.000000kVA
Real electrical input: 1,840 W

Real electrical input

0.000000W
Real generator output: 1,656 W

Real generator output

0.000000W

Results update automatically as you type.

Planning arithmetic only. Enter your own rates, capacities, efficiencies, and usage factors; no live tariffs or device defaults are used.

Use Cases

Sizing a generator for a load

Determine the required generator output power based on the electrical load's voltage, current, and power factor, accounting for generator efficiency.

Example: A three-phase load at 400V, 50A, PF 0.8, efficiency 0.9 gives output power ≈ 24.9 kW.

Estimating fuel consumption or cost

By knowing the real input power, you can estimate fuel consumption or operating cost of the generator under specific electrical conditions.

Example: If real input power is 30 kW, and fuel consumption is 0.3 L/kWh, fuel use is 9 L/h.

Frequently Asked Questions

How does the generator power calculator work?
It uses your input RMS voltage, RMS current, power factor, and generator efficiency. For single-phase, apparent power is V×I; for three-phase, it's √3×V×I. Real input power is apparent power times power factor, and real output power is real input power times efficiency.
What is the difference between apparent, real input, and real output power?
Apparent power (kVA) is the product of voltage and current. Real input power (kW) is the actual power consumed by the generator, accounting for power factor. Real output power (kW) is the usable electrical power delivered, accounting for generator efficiency.
Can I use this calculator for three-phase generators?
Yes, the calculator includes an explicit phase model. You can select single-phase or three-phase. For three-phase, it applies the √3 factor to compute apparent power correctly.

Tips & Common Mistakes

Tips

  • Ensure the power factor is between 0 and 1; typical values are 0.8 for inductive loads.
  • Generator efficiency is usually between 0.7 and 0.95; check the manufacturer's specs.
  • For three-phase systems, the calculator automatically includes the √3 factor, so enter line-to-line RMS voltage.
  • Use consistent units: voltage in volts, current in amperes, and power factors as fractions (e.g., 0.8).

Common Mistakes to Avoid

  • Entering power factor as a percentage (e.g., 80) instead of a fraction (0.8).
  • Using peak voltage instead of RMS voltage; RMS is the standard for power calculations.
  • Forgetting to select the correct phase model; single-phase and three-phase calculations differ by √3.

Last updated: August 13, 2026