Enter your electrical loads, altitude, and temperature to find the right generator size with proper derating applied.
Total Running kW
125 kW
Total Starting kW (Peak)
293 kW
Derating Factor
100.0%
Required kVA (derated)
367 kVA
Recommended Generator
400 kVA
Estimated Cost
$130,000
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Each load item has both a running wattage and a starting (surge) multiplier. The calculator sums running loads and identifies peak starting demand, then derates the generator capacity for altitude (above 1,000 ft) and ambient temperature (above 40°C / 104°F).
Common commercial generator sizes: 20, 30, 50, 75, 100, 125, 150, 200, 250, 300, 350, 400, 500, 600, 750, 1000, 1250, 1500, 2000 kVA.