Cummins QSJ5.9G vs Generac SG100 (9.0L)
The Cummins QSJ5.9G and Generac SG100 (9.0L) are both natural gas generator engines in a similar power class. Both are rated at roughly 125 kVA. Displacement is 5.9 L versus 8.9 L. The table below compares their full specifications side by side.
| Specification | Cummins QSJ5.9G | Generac SG100 (9.0L) |
|---|---|---|
| Headline rating | 125 kVA | 125 kVA |
| Standby (50 Hz) | — | — |
| Prime (50 Hz) | — | — |
| Standby (60 Hz) | 100 kWe | 100 kWe |
| Prime (60 Hz) | — | 90 kWe |
| Displacement | 5.9 L | 8.9 L |
| Configuration | L6 | V8 |
| Cylinders | 6 | 8 |
| Rated speed | 1,800 RPM | 1,800 RPM |
| Fuel | Natural Gas | Natural Gas |
| Cooling | Liquid-Cooled | Liquid-Cooled |
| Emissions | U.S. EPA Stationary | U.S. EPA Stationary |
| Dry weight | — | — |
| Origin | United States | United States |
Choosing between Cummins QSJ5.9G and Generac SG100 (9.0L)
Use this comparison as an engineering shortlist, then confirm the complete generator package against load profile, voltage, 50/60 Hz frequency, duty class, emissions rules, cooling margin, altitude, ambient temperature, enclosure design, controller features, and alternator sizing.