Generator fuel consumption varies significantly based on generator size (measured in kW), load factor (how much power is being drawn), efficiency, and maintenance practices[2]. For diesel generators, fuel use is typically measured as gallons per hour (GPH) at different load levels, with higher loads requiring more fuel per hour[1][3].
For example, a 100 kW diesel generator consumes approximately:
- 2.6 gal/hr at 1/4 load
- 4.1 gal/hr at 1/2 load
- 5.8 gal/hr at 3/4 load
- 7.4 gal/hr at full load[1][3]
Larger generators show proportionally higher consumption rates. For instance, a 500 kW unit may use about 11.0 gal/hr at 1/4 load and up to 35.7 gal/hr at full load[1][3]. Charts published by manufacturers and equipment suppliers offer guidance for a wide range of sizes:
- 20 kW: 0.6–1.6 gal/hr (1/4 to full load)
- 250 kW: 5.7–18.0 gal/hr
- 1000 kW: 21.6–71.1 gal/hr[1][3]
Factors impacting fuel efficiency include:
- Operating near 75–80% of rated load for peak efficiency
- Modern design features (electronic fuel injection, turbocharging)
- Environmental conditions (altitude, ambient temperature)
- Routine maintenance (cleaning filters, calibrating injection systems)[2]
Maintaining and monitoring fuel quality is also critical for both efficiency and the health of the generator[1]. Fuel consumption tables are intended as estimates, as actual figures may differ due to the generator’s brand, model, and specific operating environment[1].