Diesel Tank Autonomy Calculator
How long can the genset run before the next fuel delivery?
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Diesel Tank Autonomy Calculator by TheCalcTools
How the Diesel Tank Autonomy Calculator works
Enter the tank size, the usable fraction (tanks cannot be drained to zero) and the fuel use per hour.
Enter how many hours a day the genset runs.
Autonomy is usable fuel divided by daily consumption.
The formula
Worked example
Using the default values shown in the calculator:
| Tank capacity (litres) | 1000 |
|---|---|
| Usable fraction (%) | 90 % |
| Fuel use (litres per hour) | 4.3 |
| Genset running hours per day | 8 |
| Target autonomy (days) | 10 |
- Usable fuel = 1,000 × 90% = 900 L; at 4.3 L/h that is 209.3 hours.
- At 8 hours a day the tank lasts 26.2 days; a 10-day target needs 383 L.
Result:
| Usable fuel (litres) | 900 |
|---|---|
| Run time on a full tank (hours) | 209.3 |
| Autonomy (days) | 26.2 |
| Tank needed for the target (litres) | 383 |
| Refills per month at this rate | 1.1 |
Frequently asked questions
Why keep a reserve?
Fuel near the tank bottom can contain sediment and water, and running dry can airlock the fuel system. Many sites treat 10–15% as unusable.
Does consumption change with load?
Yes. Use an average from site data, or the fuel consumption calculator for your actual load.
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.