Generator Fuel Consumption Calculator
How much diesel will your genset burn at a given load?
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Your results
Generator Fuel Consumption Calculator by TheCalcTools
How the Generator Fuel Consumption Calculator works
Enter the generator’s kVA rating and rated power factor (usually 0.8).
Enter the average load as a percentage of the rated kW and the specific fuel consumption in litres per kWh.
Fuel per hour is output kW times consumption; extend to days and months with run hours and diesel price.
The formula
Worked example
Using the default values shown in the calculator:
| Generator rating (kVA) | 30 kVA |
|---|---|
| Rated power factor | 0.8 |
| Average load (% of rated kW) | 60 % |
| Specific consumption (litres per kWh) | 0.3 |
| Running hours per day | 8 |
| Days per month | 30 |
| Diesel price (PKR per litre) | Rs275 |
- Output = 30 × 0.8 × 60% = 14.4 kW.
- Fuel = 14.4 × 0.30 = 4.32 L/h, 34.6 L a day, 1,037 L a month, costing $285,120.
Result:
| Output power (kW) | 14.4 |
|---|---|
| Fuel use (litres per hour) | 4.32 |
| Fuel per day (litres) | 34.6 |
| Fuel per month (litres) | 1,037 |
| Fuel cost per month (PKR) | Rs 285,120 |
| Fuel cost per kWh (PKR) | 82.50 |
Frequently asked questions
Why is fuel use per kWh worse at light load?
A diesel engine has a fixed friction and pumping loss, so efficiency falls at low load. Running below 30–40% load wastes fuel and can cause wet stacking.
Where does 0.30 L/kWh come from?
It is a typical mid-range value. Check the manufacturer’s fuel-consumption table for your model at 50%, 75% and 100% load and use those figures.
Sources and further reading
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This calculator gives estimates for planning only. Electrical installations must be designed, checked and carried out by qualified personnel following local codes and the equipment manufacturer's data. Never rely on this result alone for safety-critical decisions. See our disclaimer.