How to Size an Industrial Generator

1. Build a usable load list

For every load record quantity, running kW or kVA, power factor, starting method, starting current, operating priority and whether it starts simultaneously. Separate essential loads from loads that can be delayed or shed.

2. Identify the largest transient

Direct-on-line motors, pumps, compressors, elevators, transformers and some UPS systems can drive generator size. Soft starters, variable-frequency drives or staged starting may reduce the required transient capacity, subject to harmonic and compatibility checks.

3. Confirm rating and environment

• Standby, prime and continuous ratings are not interchangeable.
• High altitude and high ambient temperature can reduce available output.
• Non-linear loads may require alternator and reactance review.
• Future expansion and redundancy should be explicit, not hidden in a random margin.

Send the load list

Include voltage, frequency, load sequence, largest motor, UPS details, acceptable voltage/frequency dip, altitude, ambient temperature and required redundancy.