Generator Sizing Calculator

Accurately size commercial standby or prime power generators by factoring in Phase, Voltage, Power Factor, and Motor Inrush Current.

Electrical System

Load Profile

Total Running kVA
207.8 kVA
Apparent power required to run the continuous load.
Total Running kW
166.3 kW
Real power consumed by the continuous load.
Required Motor Starting Surge (SkVA)
623.5 SkVA
The instantaneous peak power required to start heavy induction motors without stalling the generator.
Minimum Recommended Generator Size
249 kW
(Which is 312 kVA @ 0.8 PF). This includes your 20% safety margin and factors in the required alternator size to handle motor starting surge.

Understanding the Results

Why is the Recommended Size higher than Running kW?

Generators should generally not operate continuously at 100% capacity. This calculator automatically adds your selected safety margin (default 20%) to ensure the generator runs comfortably at roughly 80% load.

Additionally, if your Motor Starting Surge (SkVA) is extremely high, the calculator will drastically upsize the generator recommendation. Standard generator alternators can handle roughly 2x their nameplate kVA rating in short-term starting surge before the voltage drops to dangerous levels (which would cause magnetic contactors to chatter and disconnect). If your motors pull a massive 6x Locked Rotor Amp surge, you are forced to buy a massive generator just to handle the first 3 seconds of startup.

Learn More About Generator Sizing