The table estimates diesel consumption for generator sets from 20 to 1000 kVA at four load points. It is meant for planning fuel deliveries, tank sizes and running costs before the manufacturer's datasheet for a specific set is available; once you have that datasheet, its figures replace these.
Sets are rated in kVA at a power factor of 0.8, so a 100 kVA set delivers 80 kW at full load. Fuel follows the kW actually delivered, not the kVA rating, and diesel engines burn more fuel per kWh at light load.
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Estimated fuel use by generator size
Litres per hour. Generic part-load curve, 0.24 L/kWh at full load. Each size links to its own page with daily use and tank runtime.
P (kW) = S (kVA) × 0.8 × load %
SFC(load) = 0.24 L/kWh × k(load)
k = 1.4 (25 %), 1.12 (50 %), 1.03 (75 %), 1 (100 %)
F (L/h) = P × SFC(load)
The full-load figure of 0.24 L/kWh (about 200 g/kWh at a diesel density of 0.835 kg/L) lies within the range quoted for modern sets. The multipliers k describe a generic, deliberately cautious part-load curve. Neither is any manufacturer's data.
Small sets often use more fuel per kWh than this curve and large modern sets less. A datasheet consumption at 25, 50, 75 and 100 % load is the reliable source.
The values assume a steady load. Warm-up, idling, frequent load changes, poor maintenance, high altitude and hot intake air all raise real consumption.
Running a diesel set for long periods at light load is inefficient and can lead to wet stacking; the guide on why generators burn more fuel than expected explains the checks.
Fuel consumption by generator size
Each page adds litres per kWh, US gallons, 8- and 24-hour totals and the runtime of an example tank.