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Generator Sizing Calculator

Estimate generator kW and kVA from continuous load, largest motor load, starting multiplier, power factor and reserve margin.

✓ Method reviewed · 2026-08-22
CALCULATORWhat generator kVA class do my loads need?

Results are for information and preliminary estimation. For critical technical work, manufacturer data, local codes and qualified professional review take precedence.

CALCULATION ENGINEGENERATOR-SIZE · R1.5.1Engine and route QA: PASS · Method and limits visible
Trust & methodology →
1Enter real inputs
2Press Calculate
3Read result with assumptions
Method & assumptions

How is it calculated?

Estimated peak active power = continuous load plus the motor's additional starting demand. kVA ≈ kW / power factor, then reserve is added. Confirm with generator transient data.

Example

Example: A 4 kW base load plus a 1.5 kW motor with 3× starting demand can require a generator well above the running-load total.

What questions does this tool answer?

  • What generator kVA class do my loads need?
  • How is Generator Sizing calculated?
  • What inputs are needed for Generator Sizing?
WHAT CHANGES THE RESULT

Check these before using the estimate

Electrical and energy calculations are not final designs by themselves. Load profile, conductor conditions, protection, efficiency and local codes must be considered together. Sorsana tools are intended for preliminary sizing and scenario comparison.

  • Continuous and surge characteristics of the real load
  • Cable length, conductor material and ambient temperature
  • Battery, charger and inverter efficiency plus usable capacity
  • Manufacturer data and applicable local electrical codes
FAQ

Frequently asked questions

Why does motor starting matter?+

Induction motors can impose several times their running electrical demand while starting.

Is this a final selection?+

No; alternator transient response, drives and load sequencing must be checked.