How much diesel will your DG set burn?
Enter the rating and how hard the set is working. The calculator derives the answer from two assumptions you can see and change — no hidden table, no numbers we cannot show you the arithmetic for.
litres per hour equals kVA times power factor times load percent times specific fuel consumption
PF power factor (0.8 by convention for Indian DG ratings) · SFC specific fuel consumption, litres per kWh produced
This is an estimate derived on this page, not a manufacturer figure. SFC defaults follow the load band you choose, because a diesel is least efficient when lightly loaded. For a contractual number, use the fuel-consumption curve on your engine model’s datasheet — that one is measured, this one is derived.
Assumptions — change them if you know better
- Electrical load
- —
- Per 8-hour shift
- —
- Per 24 hours
- —
- Fuel cost per hour
- —
- Fuel cost per 8-hour shift
- —
Planning estimate. Real consumption moves with ambient temperature, altitude, fuel quality, engine condition and your load’s actual power factor.
Why one flat figure would be wrong
Efficiency changes with load
Part of the fuel goes to running the engine at all, before any of it becomes electricity. That overhead is roughly fixed — so the lighter the load, the more litres each unit costs.
| Load | Typical SFC (L/kWh) | What it means in practice |
|---|---|---|
| 25% | 0.28 | Least efficient — and below ~30% for long spells, wet stacking starts |
| 50% | 0.23 | Common real-world average on standby duty |
| 75% | 0.21 | The efficiency sweet spot for most sets |
| 100% | 0.21 | Full load — efficient, but no headroom for surge |
Worked example
A 125 kVA set at 75% load: 125 × 0.8 = 100 kW rated, drawing 75 kW. At 0.21 L/kWh that is 75 × 0.21 = 15.8 litres an hour — about 126 litres over an 8-hour shift. Drop the same set to 25% load and it draws 25 kW, but at roughly 0.28 L/kWh it still burns 7.0 litres an hour: a third of the output for nearly half the fuel.
The expensive mistake is upstream
Rating a set generously feels safe and bills you for it forever — worse litres per unit, and the maintenance tail of long-term light running. Size for the starting surge you actually have, not for a margin on top of a margin.
Fuel and running costs, answered
Frequently asked questions
How is the litres-per-hour figure calculated?
In two steps, both shown on the page. First the electrical load: kW = kVA × power factor (0.8 by convention for Indian DG ratings). Then the fuel: litres/hour = kW drawn × specific fuel consumption (L/kWh). A 125 kVA set at 75% load draws about 75 kW, and at roughly 0.21 L/kWh that is about 15.8 litres an hour. Nothing here is looked up from a table — you can reproduce every number with a calculator.
How accurate is this against the real thing?
Treat it as a planning estimate, not a quotation. Real consumption moves with ambient temperature, altitude, fuel quality, engine hours, how well the set is maintained, and the actual power factor of your load rather than the assumed 0.8. For a contractual number, use the fuel-consumption curve on your engine model’s datasheet — that figure is measured, this one is derived.
Why does consumption per unit get worse at low load?
Because a share of the fuel goes to running the engine at all — friction, pumping, driving the fan and accessories — before any of it becomes electricity. That overhead is roughly fixed, so as useful output falls it is spread over fewer kWh and the litres-per-kWh figure rises. It is also why a heavily oversized set costs more per unit than a right-sized one, every hour it runs.
What is wet stacking, and does this matter for sizing?
Running a diesel far below its rated load for long periods stops the engine reaching proper combustion temperature. Unburnt fuel and soot then collect in the exhaust — "wet stacking" — glazing bores, fouling injectors and turbos, and shortening life. It is a maintenance bill caused by a sizing decision, which is why the honest answer to "how big?" is sometimes smaller than the one that sounds safe. Our kVA sizing calculator sizes for starting surge without inflating the rating.
Does a CPCB IV+ set use more diesel?
Not meaningfully as a rule — IV+ compliance is mostly about aftertreatment and emissions control rather than a fuel-economy penalty. What IV+ sets do add is DEF/AdBlue consumption on SCR-equipped engines, which is a separate consumable with its own running cost. Budget it alongside diesel, not inside it.
Should fuel be in the rental contract or billed separately?
Both are normal, and the difference matters more than the rate does. Fuel is usually on the client’s account with the set supplied at an agreed level and returned the same way, because consumption is driven by how the site runs the machine, not by the machine. What matters is that the basis is written down — level in, level out, who refuels, and at whose rate.
Reply within 4 working hours. Engineered offer within 24 hours.