Is Diesel Going Missing From Your DG Set? Litres vs Running Hours, Reconciled (₹)
Is someone taking diesel from your DG set? Check the litres against the hour meter. As of 16 Oct 2026 a 250 kVA set uses about 34–42 litres an hour at 60% load (Mahindra's datasheet; BEE field data), and diesel costs ₹95.20 a litre in Delhi (PPAC). In our worked example, 750 unexplained litres a month cost about ₹71,000.
Last checked: 17 Oct 2026
By the Mama Editorial Team. Figures carry source and date; our own inputs are marked "assume".
Key takeaways
- Expected diesel is a number you can calculate. Running hours × load in kW × litres per kWh gives what the set should have burnt. Mahindra Powerol lists its 250 kVA set at 41.2 litres an hour at 75% load and 54.1 at 100% (checked 17 Oct 2026).
- Field sets burnt more than this datasheet. In the Bureau of Energy Efficiency's DG set monitoring table (Table 9.5), the 21 sets with readings ran at 0.290 to 0.362 litres per kWh.
- Some gap is not theft. An IPPTA paper found storage stock short by 1.5–3% per 12 kL tanker load because hot return diesel distorts the dip.
- In NCR the log book is already mandatory. DPCC's SOP of 03.06.2025 cites a CAQM letter of 31.01.2025 stating that a DG log book is mandatory (pp. 11–12). The same log is your diesel control.
- A camera shows who opened the tank and when the set ran, not how many litres.
Why litres against hours is the right test
A properly loaded diesel generator turns fuel into kilowatt-hours at a fairly steady rate. So you can predict its consumption from two numbers it already records: hours run and load carried.
BEE's guidance says engine loading "needs to be maintained above 50%" for good performance (BEE, DG Set System, section 9.3). Mahindra's own sheet shows litres per kWh rising as load falls (0.27 at full load, 0.275 at 75%), so a lightly loaded set can look like a leaking one.
The test has three sides: litres the set should have used, litres the stock records say it used, and litres you bought. If they agree within a known tolerance, the diesel is accounted for. If not, the size and pattern of the gap tell you where to look.
What a power cut costs in idle lines and the diesel premium is a different question, covered in our guide to power cuts and DG set limits and the power cut and DG downtime calculator.
Step 1: work out the expected litres per hour
From the datasheet. Mahindra Powerol's 250 kVA model (prime 200 kW, engine mPower63105G) is listed at 41.2 L/h at 75% load and 54.1 L/h at 100% load (checked 17 Oct 2026). That is about 0.275 L/kWh at 150 kW and 0.27 L/kWh at 200 kW. Use your own set's sheet.
If your sheet gives grams per kWh. Litres per hour = g/kWh × kW ÷ density in g/L. Hindustan Petroleum's BS-VI diesel specification puts density at 15 °C between 810 and 845 kg/m³. At an assumed 830 g/L, the Mahindra 75% figure works out to about 228 g/kWh.
From the field. BEE's monitoring table lists 22 sets, 21 with readings, between 0.290 and 0.362 L/kWh; the HSD sets of 160–640 kW derated capacity ran at 0.290 to 0.349. All of them ran at 65–110% of derated capacity, so the table gives no benchmark for a lightly loaded set.
From your own set. The most defensible baseline: BEE describes a two-hour trial at steady load with fuel consumption logged "by dip level or by flow meter" every 15 minutes, along with kW and kWh (section 9.4).
| Basis (250 kVA set, 60% load = 120 kW) | Litres per kWh | Expected litres per hour | Source |
|---|---|---|---|
| Datasheet, adjusted for part load | 0.28 (assume) | 33.6 | Mahindra 41.2 L/h at 75% |
| BEE field, middle | 0.33 (assume) | 39.6 | BEE Table 9.5 range |
| BEE field, top of HSD rows | 0.349 | 41.9 | BEE Table 9.5 |
| Your own two-hour trial | measured | measured | BEE section 9.4 method |
In NCR, CAQM's schedule lets sets of 41 kW to under 800 kW comply through dual-fuel mode or a retrofitted emission control device (Direction No. 76, 29.09.2023, as amended 11.12.2024). Dual-fuel sets draw part of their energy from gas. Expected diesel per kWh is then lower, and the trial on your own set is the only reliable baseline.
Step 2: get the four records that make the reconciliation
- Tank dip log. Opening and closing dip for the month, read off the tank's calibration chart, at the same time of day and with the set cold. The base tank on the Mahindra 250 kVA set holds 425 litres, about ten hours at 75% load. If you also have a bulk tank, dip both.
- Hour meter. Reading at the start and end of the month, written into the log book, not taken from memory.
- Load or energy record. The kWh meter on the DG panel, if fitted, is the best single number. Without one, hourly kW or ampere readings from the panel give average load. BEE notes the average load "can be easily assessed by logging the current drawn at the main switchboard".
- Delivery receipts. Every tanker or barrel delivery with the challan quantity, the dip before and after filling, and who signed for it.
Two control questions sit alongside: who holds the key to the tank cap and drain valve, and is the hour meter sealed? Neither accuses anyone; both decide whether the numbers can be trusted.
Step 3: reconcile the month
Litres consumed = opening stock + litres received − closing stock. Litres expected = hours × average kW × litres per kWh, plus a measurement allowance.
In a paper in the IPPTA journal (Vol. 13, No. 4, December 2001), D.K. Singhal of Chandpur Enterprises found storage stock at mill DG sets short by 1.5–3% after each 12 kL tanker load, or 200–350 litres. Hot return diesel at about 80 °C swelled the volume in the service tank and distorted the dip. His remedy: multiply calculated consumption by 1.03–1.05. Allow for that before calling anything missing.
Worked ₹ example: one month, 250 kVA set
The plant is hypothetical. Every input below is an assumption except the diesel price and the BEE consumption figure.
- Set: 250 kVA, 200 kW prime, straight diesel, running at an average 60% load (120 kW). Assume this average comes from hourly panel readings.
- Hours: assume the hour meter moved 80 hours in the month.
- Expected rate: 0.349 L/kWh, the top of BEE's HSD rows, so the test is generous to the set.
- Measurement allowance: 3%, the top of the IPPTA range.
- Diesel: ₹95.20 a litre, IOC retail in Delhi on 16 Oct 2026, per PPAC. Use the rate on your own invoice; state VAT and bulk supply terms change it.
- Stock: assume an opening dip of 1,200 L, two deliveries totalling 4,000 L, and a closing dip of 1,000 L.
| Line | Working | Litres | ₹ at ₹95.20/L |
|---|---|---|---|
| Consumed, per stock records | 1,200 + 4,000 − 1,000 | 4,200 | 3,99,840 |
| Expected, per hours and load | 80 h × 120 kW × 0.349 L/kWh | 3,350 | 3,18,920 |
| Measurement allowance | 3% of expected | 101 | 9,615 |
| Expected incl. allowance | 3,451 | 3,28,535 | |
| Unexplained gap | 4,200 − 3,451 | 749 | ~71,300 |
| Same gap over 12 months | × 12 | 8,988 | ~8.6 lakh |
The gap is about 18% of the month's diesel. If the DG panel has a kWh meter reading 9,600 kWh for the month, the set appears to burn 0.44 L/kWh (4,200 ÷ 9,600). That is well above every set in BEE's table.
Now change one assumption: a camera timeline or the panel's event log shows the set ran 92 hours, not the 80 logged. Expected litres become 92 × 120 × 0.349 × 1.03, or about 3,968. The gap shrinks to about 232 litres, or ₹22,000. Most of the problem was unlogged hours, not missing diesel, which is why hours get checked before litres.
What a gap can mean (and how to tell)
| Pattern you see | Possible explanation | Check |
|---|---|---|
| Gap of 1.5–3%, steady month to month | Hot return diesel and dip error (IPPTA, 2001) | Dip cold, same hour; apply the allowance |
| Litres per kWh high, hours match | Light load, worn injectors, or the set is due for a trial | BEE two-hour trial at steady load |
| Hours on the meter below hours the set actually ran | Unlogged runs: weekends, tests, a neighbouring unit fed off the set | Panel event log or camera timeline vs log book |
| Gap appears right after deliveries | Short delivery against the challan | Dip before and after every fill, signed by two people |
| Gap appears when the set is idle | Drain valve or cap opened, or a leak | Seal the drain valve, check the tank bund and floor |
| Stock fine, purchases high | Diesel issued to vehicles or other uses from the same tank | Separate issue register for every non-DG use |
The patterns are about equipment and records, not people. A gap shows which control is weak; who, if anyone, is responsible is a separate inquiry needing more than a spreadsheet.
The NCR angle: the log book CAQM already requires
Plants in Delhi NCR have a second reason to keep these records. CAQM's Direction No. 76 (29.09.2023) allows DG sets to run "only as a backup against regular power supply failures".
The Delhi Pollution Control Committee's SOP of 03.06.2025, filed as Annexure I to its 2026 reply before the National Green Tribunal (pp. 11–12), cites a CAQM letter of 31.01.2025. The letter says "maintenance of log book for operation of DG set is mandatory". For a non-compliant set with no log book or other established record, environmental compensation is levied from 01.10.2023 onwards. The SOP also asks for an affidavit confirming the set ran "for the hours/ days mentioned in the logbook".
The revised GRAP, Direction No. 104 dated 29.09.2026, puts "Ensure that diesel generator sets are not used as regular source of power supply" in Stage I (item 17), invoked for "Poor" air quality (Delhi AQI 201–300).
The same log book protects the plant before the pollution board and supplies the hours side of the diesel reconciliation. A log that understates hours is a problem twice over. Direction No. 76 covers sectors in NCR only.
What cameras can and cannot tell you here
They can give an independent timeline of the set. A camera on the DG panel can show the running and fault lamps; our zone spec for panel rooms and DG rooms works out the pixels needed to see a 22 mm lamp. A camera on the tank, fill point and DG room door shows when a tanker arrived, when the cap or drain was opened, and whether containers left the room. That is the "who opened the tank, and when" half of the question.
They cannot read litres, check a dip, judge a short challan or see a slow leak. The dip chart, hour meter and kWh meter are the measurements; a camera is a witness, set against the records, as in our piece on theft and shrinkage in Indian factories. Footage of recognisable workers is personal data under s.2(t) of the DPDP Act, 2023; tell workers in writing what is recorded and why (see the worker CCTV notice under DPDP).
Where Mama fits
Mama reads a factory's existing cameras and sends the owner a short plain-language note each morning about where hours and money leaked the day before. For a DG set, that can include when the set started and stopped according to the panel camera, ready to set against the log book's hours. It watches machines, panels and doors, not individuals. Mama can also draw a camera plan for the DG room, tank and fill point. Leave an email or phone in the form below.
FAQ
How many litres per hour does a 250 kVA DG set use? Mahindra Powerol lists its 250 kVA set (200 kW prime) at 41.2 litres an hour at 75% load and 54.1 at full load (checked 17 Oct 2026). At 60% load, expect roughly 34–42 litres an hour, based on that sheet and BEE's field range.
How do I calculate expected diesel consumption from running hours? Multiply hours run by average load in kW and by litres per kWh, from the datasheet, BEE's field range or your own trial. Add a measurement allowance of about 1.5–3% for dip error. Compare the result with opening stock plus deliveries minus closing stock.
How much difference between expected and actual diesel is normal? A steady 1.5–3% fits dip error from hot return diesel (IPPTA, December 2001). A larger gap, or one that jumps after deliveries or idle periods, points to a weak control.
Is a DG log book mandatory in Delhi NCR? Yes. DPCC's SOP of 03.06.2025 cites a CAQM letter of 31.01.2025 stating that maintaining a log book for DG set operation is mandatory. For a non-compliant set without one, environmental compensation can be levied from 01.10.2023 onwards.
Can CCTV prove diesel theft from a generator? On its own, no. A camera can show when the tank was opened, when a tanker came and when the set ran, but it cannot measure litres.