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ElecToolsHQ

Generator Sizing Calculator

Calculate the required generator size from total load and a derating factor (Size = Load ÷ Derating Factor).

Safety margin applied to the load, between 0 and 1.

Formula

Size = Load ÷ Derating Factor

Size
Required generator size, in kilowatts
Load
Total connected load, in kilowatts
Derating Factor
Safety margin, between 0 and 1

What this calculator does

Calculates the generator capacity needed to handle a connected load with a safety margin.

Use cases

  • Size a backup generator for a facility's total connected load
  • Check whether an existing generator has enough margin for a load increase
  • Compare required generator size across different derating assumptions

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