Two Capacity Limits
kW represents real power delivered to loads. kVA represents voltage-current capacity. A generator may be limited by engine power in kW and alternator current or heating in kVA.
kW = kVA × PF
Running Load
Add loads expected to operate simultaneously, not every connected nameplate unless all can run together. Include realistic power factor and conversion efficiency.
A 40 kW aggregate load at 0.8 PF requires 50 kVA before reserve margin.
Starting and Load Steps
Motor starting and transformer inrush can dominate selection. The generator must maintain acceptable voltage and frequency during the largest expected step, which depends on alternator, engine, excitation, controls, and load sequence.
Environmental and Load Effects
Altitude, temperature, fuel type, emissions configuration, nonlinear loads, harmonics, UPS systems, welding loads, and duty rating can reduce usable capacity.
Use manufacturer transient-sizing software or engineering support for final selection.