Diesel Generator Fuel Consumption: Liters per Hour by Load
By Tommy, Export Sales Manager at Zhiqiang Power · tommy@zhiqiang-power.com · Last reviewed 2026-09-17 against factory load-bank data
Fuel is the largest lifetime cost of a diesel generator, usually several times the purchase price over ten years. Every quotation we receive asks the same two questions: how many liters per hour, and what will that cost me per kWh. This page answers both with real numbers from our own catalogue.
All figures below are for standard automotive diesel (0# in summer, -10# or -35# in cold conditions), at ISO 3046-1 reference conditions, on sets with Yuchai engines and an electronic governor.
The short answer
A 100 kW diesel generator burns about 24 liters per hour at full load, roughly 18.5 L/h at 75% and 13.2 L/h at 50%, measured against ISO 3046-1 reference conditions.
- ›Diesel burn tracks the work being done, not the size of the set: a 500 kW machine idling at light load can burn less per hour than a 100 kW set at full tilt.
- ›The honest comparison number is specific fuel consumption in g/kWh, published on every product page of this catalogue.
- ›Long spells below about 30% load are bad for the engine: unburned fuel glazes the bores and builds up carbon (wet stacking).
- ›Every figure on this site is declared against ISO 3046-1 and confirmed on our load bank before shipment.
How fuel use changes with load
Take our 100 kW set (Yuchai YC6B180L-D20, specific fuel consumption 200 g/kWh or better). On the factory fuel curve it burns 13.2 L/h at half load, about 18.5 L/h at three-quarters load and 24 L/h at full load. The curve is not a straight line: the engine is most efficient, per kilowatt produced, somewhere between 50% and 80% of prime power.
That is why we size sets against the actual duty. A generator chosen "with room to grow" that spends its life at 20% load will sip fewer liters per hour than a fully loaded one, but it burns more fuel per kWh delivered, and it will need injector and exhaust work earlier.
L/h and L/kWh across the catalogue
The table is generated from the same datasheet values published on each product page, so the two can never disagree. L/kWh at full load simply divides the hourly burn by the prime rating.
| Model | Prime | 50% (L/h) | 75% (L/h) | 100% (L/h) | L/kWh at 100% |
|---|---|---|---|---|---|
| TFW-50 | 50 kW / 62.5 kVA | 7 | 10 | 13 | 0.26 |
| TFW-100 | 100 kW / 125 kVA | 13 | 18.5 | 24 | 0.24 |
| TFW-200 | 200 kW / 250 kVA | 29.2 | 41.6 | 54 | 0.27 |
| TFW-300 | 300 kW / 375 kVA | 40 | 57 | 74 | 0.25 |
| TFW-500 | 500 kW / 625 kVA | 65.3 | 93.2 | 121 | 0.24 |
| TFW-800 | 800 kW / 1000 kVA | 102.1 | 145.5 | 189 | 0.24 |
Derived from the factory datasheets behind each model page. L/kWh at full load = L/h ÷ prime kW. Declared against ISO 3046-1 reference conditions; the load-bank record for your unit ships with the set.
Working out your own fuel budget
Multiply liters per hour by your local diesel price, then divide by the kW you actually draw. A 100 kW set at 75% load uses about 18.5 L/h; with diesel at USD 0.90 per liter, that is roughly USD 16.65 per hour, or about USD 0.22 per kWh delivered.
For a standby set that runs a few hours a month, fuel cost barely matters and reliability does. For prime power on an island or a mine, it dominates everything, which is why those projects look hard at specific fuel consumption, load factor and maintenance intervals before they look at price.
Related reading
- Browse all generator sets with full fuel curves →
- Data center duty (fuel budgeting matters most here) →
Power ratings follow ISO 8528-1:2018 (Prime PRP / Standby ESP), and the fuel figures are stated at ISO 3046-1:2002 standard reference conditions. Both are confirmed unit by unit on our load bank, and the test record ships with the set. Standby figures are the engine's factory standby rating from the model spectrum table — never a computed 110% of the rated output. Noise figures are typical open-type reference values, not a guaranteed sound-power level.
Frequently Asked Questions
How many liters per hour does a 100 kW diesel generator use?▼
About 24 L/h at 100% load, 18.5 L/h at 75% and 13.2 L/h at 50%, on the published Yuchai YC6B180L-D20 curve. Real consumption moves with altitude, intake temperature and fuel quality, so treat these as budgeting figures and confirm against the load-bank record that ships with your set.
At what load is a diesel generator most fuel efficient?▼
Between roughly 50% and 80% of prime power. Below about 30% for long periods the engine runs cool and leaves unburned fuel in the exhaust and on the bores (wet stacking). Above 100% the burn per kWh climbs again, and overload is limited to one hour in every twelve.
How do I convert L/h into cost per kWh?▼
Cost per kWh = (L/h x fuel price per liter) / kW actually delivered. Example: 18.5 L/h at USD 0.90 per liter, producing 75 kW, works out at about USD 0.22 per kWh. Use the g/kWh figure on the product page when you need to compare two engines directly.
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