Electrical Tools

Generator Size Calculator

Calculate kW and kVA needed for home backup, construction sites, and commercial applications. Includes motor starting surge requirements.

Load Requirements

Generator Sizing

Minimum Size 0 kW
Surge/Starting 0 kW
Running Load 0 kW
Starting Surge 0 kW
Recommended Size 0 kW
Amps at 240V 0 A
Fuel (gas) per hour 0 gal/hr
Est. Generator Cost $0

Common Loads

  • AC (3 ton): 3.5 kW run / 7 kW start
  • Well Pump (1HP): 1 kW run / 3 kW start
  • Water Heater: 4.5 kW
  • Electric Range: 8-12 kW

Formula

Running Load = Sum of all loads

Starting Surge = Largest motor × 3

Min Size = Running Load × Safety

Rec Size = Max(Running, Surge)

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