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Generator Derating: Altitude & Temperature

Altitude and ambient temperature reduce every rating. Convert your site conditions into usable kW and the nameplate you must order.

Inputs

Inputs and assumptions

Feet above sea level.

Air-cooled and gaseous-fuel sets derate faster than large water-cooled diesels.

Verify against the manufacturer table; 1% per 10 F is a common default.

Result

Altitude portion
—
Nameplate rating to order
—
Shortfall of the candidate set
—
Temperature portion
—
Total derating
—
Usable rating at this site
—

What to check

  • Manufacturer derating table for the exact model
  • Site design temperature and elevation from a survey, not a phone app

Related calculators

Load arithmetic only. Nameplate watts, motor starting data, and the adopted electrical code edition govern the real answer; a licensed electrician or engineer signs off the design.

Saved calculations

Keep the assumptions with the result.

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