Generator Sizing Calculator
The Generator Sizing Calculator finds the standby genset kVA for a load, accounting for the largest motor's starting kVA surge. Example: for a 100 kW load with a 20 HP DOL-started largest motor, Recommended genset = 250 kVA, Steady demand = 129.41 kVA, Peak during start = 215.16 kVA (per ISO 8528-1:2018 | ISO 3046-1 | IEEE 446 | PEC 2017 | NFPA 110).
How it works
Computed from your inputs per ISO 8528-1:2018 | ISO 3046-1 | IEEE 446 | PEC 2017 | NFPA 110.
Worked example (Electrical & Power)
Inputs: a 100 kW load with a 20 HP DOL-started largest motor.
| Result | Value |
|---|---|
| Recommended genset | 250 kVA |
| Steady demand | 129.41 kVA |
| Peak during start | 215.16 kVA |
Computed live by WorkHive's calculation engine; standard: ISO 8528-1:2018 | ISO 3046-1 | IEEE 446 | PEC 2017 | NFPA 110.
How to use this calculator
- Enter the figures for the duty you are sizing: the worked example below uses a 100 kW load with a 20 HP DOL-started largest motor.
- The calculator returns Recommended genset, Steady demand, Peak during start, computed per ISO 8528-1:2018.
- Check the worked example to confirm the method matches how you would do it by hand, then run your own numbers in the interactive tool.
FAQ
What is a genset sizing calculator kVA?
The Generator Sizing Calculator is a free online tool that computes finds the standby genset kVA for a load, accounting for the largest motor's starting kVA surge. It shows the formula and a fully worked example so you can check the method, not just the number.
How is it calculated?
The result is computed from your inputs following ISO 8528-1:2018. The worked example on this page shows a real computation with real numbers.
Is the calculator free?
Yes. WorkHive's engineering calculators are free to use, no sign-up needed for the tools. WorkHive is a free, offline-first maintenance platform built for Philippine industrial plants.
Run it on your own numbers
Open the interactive Generator Sizing Calculator in WorkHive: free, no sign-up needed for the calculators.