How this calculator works
Electrical output is voltage times current for DC and includes power factor for AC. A balanced three-phase supply adds a sqrt(3) multiplier when voltage is measured line to line. Shaft power is electrical real power divided by generator efficiency. Apparent power determines current loading even when real power is lower. This is a power calculation, not an appliance inventory or generator product selector.
Formula
DC: P = V I. Single phase: S = V I. Three phase: S = sqrt(3) VLL IL. P = S PF; Pshaft = P/eta; hp = Pshaft/745.6998716.
Worked example
A DC generator delivering 100 V at 10 A produces 1000 W. At 80% efficiency it requires 1250 W of shaft input. A balanced 100 V, 10 A three-phase output at PF = 0.8 produces 1385.64 W.
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Frequently asked questions
Should I enter phase or line voltage?
Use line-to-line voltage for the three-phase option. For single phase, use the voltage directly across the load.
Does this include engine starting or surge ratings?
No. Motor starting, transient response, altitude and temperature derating need separate checks against generator specifications.
Why show both watts and VA?
Watts measure real power. VA measures voltage-current loading and can be higher for an AC load with power factor below one.