Generator Power Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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A fast generator power estimate is valuable only when the setup is clear. A quick circuit result is most useful when you can trace it back to the exact voltage, current, impedance, frequency, and topology assumed by the formula. The sections below show exactly what this page calculates, how to enter the data, and where the simplified model stops.

What this calculator does

The calculator isolates the relationship between Current, Voltage, Power factor and generator real power. That makes it useful for testing how one input changes the answer without mixing in unrelated assumptions.

How to use it

Fill in Current, Voltage, Power factor, Efficiency (η) exactly as defined on the page. Set Power supply type to match the solve path you want. After calculating, change one influential input slightly and confirm that the result moves in the direction predicted by the equation; this is a quick unit and setup check.

How the calculation works

Apparent power is S = kVI, with k = 1 for single phase and √3 for three phase. Real electrical power is P = S·PF. The page then estimates mechanical horsepower as P/(745.7·η).

Example

With the default setup (Power supply type = Single phase; Current = 10 A; Voltage = 230 V; Power factor = 0.8), the page reports generator real power of 1,840 W. Once this baseline matches, change only one quantity at a time so you can see which variable is controlling the result.

How to interpret the result

The generator real power belongs to the ideal relationship shown above. Keep voltage, current, frequency, impedance, duty cycle, and component units consistent, then compare the result with real component limits rather than using it as the limit itself.

Limitations and notes

This is an electrical planning relationship, not a generator-selection standard. Starting surge, nonlinear loads, harmonics, altitude/temperature derating, phase imbalance, motor starting, manufacturer limits, and required reserve capacity can materially change generator sizing.