Generator Sizing: 20 to 80
Standby and prime-rated diesel generator sizing data from 20kW to 2000kW per NEMA MG1 and ISO 8528-1. Includes standby vs prime kW, kVA rating, motor starting kVA (skVA), fuel consumption, altitude derating (3.5%/1000ft), and ambient temperature derating (3%/10C above 40C) per major manufacturer specifications.
| rating kw | alt derate pct per 1000ft (%/1000ft) | fuel consumption gph full load (gal/hr) | notes | phases (dimensionless) | power factor (dimensionless) | prime kw (kW) | rated kva standby (kVA) | rated voltage V | standby kw (kW) | starting skva (kVA) | temp derate pct per 10C above 40C (%/10C) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 20 | 3.5 | 2 | 20kW standby; DOL motor starting up to ~10HP | 3 | 0.8 | 18 | 25 | 120_208_240_480 | 20 | 160 | 3 |
| 30 | 3.5 | 2.8 | 30kW; common light commercial | 3 | 0.8 | 27 | 38 | 120_208_240_480 | 30 | 225 | 3 |
| 45 | 3.5 | 4 | 45kW | 3 | 0.8 | 40 | 56 | 120_208_240_480 | 45 | 315 | 3 |
| 60 | 3.5 | 5.5 | 60kW; common data center UPS bypass | 3 | 0.8 | 54 | 75 | 120_208_240_480 | 60 | 450 | 3 |
| 80 | 3.5 | 7 | 80kW | 3 | 0.8 | 72 | 100 | 120_208_240_480 | 80 | 560 | 3 |
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