A power cut costs a factory twice: the production lost while the line stands and restarts, and the diesel burned in the DG set to keep part of it running. With 12 cuts a month of 40 minutes, half covered by the DG, a 20-minute restart loss each time, a ₹1,500 line hour rate, 30 litres of diesel an hour and diesel at ₹90 a litre, that is about ₹1.44 lakh of lost production plus ₹1.30 lakh of diesel, or ₹2.74 lakh a year. This calculator works out both halves from your own numbers.
How the calculator works
The calculator takes seven inputs:
- Power cuts a month. Count every interruption that stops the line, including short trips that last a minute. Your DG log is a better source than memory.
- Average cut length (minutes). From supply off to supply back.
- Restart loss per cut (minutes). Time lost after power returns before the line makes good output again: machine warm-up, re-heating moulds or dies, purging, resetting controllers, scrapping the half-made parts. On some lines this is longer than the cut itself.
- Share of cut time covered by the DG (%). The part of the cut during which the DG keeps this line running. If the DG carries only lights, compressors and the office, enter 0% for this line.
- Line hour rate (₹/h). What an hour of this line costs you. The guide on machine hour rates shows how to build one.
- DG fuel use (litres per hour). At the load the DG actually carries, from the manufacturer's fuel chart or your own diesel log. Fuel use changes with load, so do not use the full-load figure for a lightly loaded set.
- Diesel price (₹ per litre). What you actually pay, delivered.
The formulas:
Lost minutes per cut = cut length × (1 − DG cover) + restart loss
Lost production per year = cuts a month × lost minutes per cut ÷ 60 × line hour rate × 12
DG hours per year = cuts a month × cut length × DG cover ÷ 60 × 12
Diesel per year = DG hours × litres per hour × diesel price
Total = lost production + diesel
The restart loss is charged on every cut, including the ones the DG covers. Unless the line rides through the changeover without stopping, power drops for a moment while the DG starts and takes the load, and the line restarts anyway. If yours genuinely does not stop, enter a smaller restart loss.
Worked example (India)
An injection-moulding line on an industrial feeder that sees regular interruptions. All figures are assumptions for illustration; they are the calculator's default inputs.
| Input | Value | Basis |
|---|---|---|
| Power cuts a month | 12 | assumption |
| Average cut length | 40 min | assumption |
| Restart loss per cut | 20 min | assumption: re-heat, purge, first-shot rejects |
| DG cover | 50% | assumption |
| Line hour rate | ₹1,500/h | assumption |
| DG fuel use | 30 L/h | assumption |
| Diesel price | ₹90/L | assumption, below the current pump price (see below) |
| Lost minutes per cut | 40 min | 40 × 50% + 20 |
| Lost hours a month | 8 h | 12 × 40 ÷ 60 |
| Lost production per year | ₹1.44 lakh | 8 × ₹1,500 × 12 |
| DG hours per year | 48 h | 12 × 40 × 50% ÷ 60 × 12 |
| Diesel per year | ₹1.30 lakh | 48 × 30 × ₹90 = ₹1,29,600 |
| Total | ₹2.74 lakh a year |
Two things stand out. First, half of the lost production here is restart loss, not the cut itself: 20 of the 40 lost minutes per cut come after power is back. Cutting restart time with a written restart routine is often cheaper than more DG cover.
Second, under these inputs an hour of DG costs ₹2,700 in diesel (30 L × ₹90), more than the ₹1,500 line hour rate it protects. Set DG cover to 0% and the total falls to ₹2.16 lakh; set it to 100% and it rises to ₹3.31 lakh. That does not mean you should switch the DG off. The line hour rate is a cost rate, not the margin on an urgent order, and it ignores missed dispatches. It does mean the DG should carry the lines where an hour matters most, not every load in the plant.
Diesel at the pump is higher than the default. The retail price of diesel in Delhi was ₹95.20 a litre on 13 October 2026 (₹97.83 in Mumbai, ₹99.55 in Chennai, ₹99.82 in Kolkata), according to the Petroleum Planning and Analysis Cell (PPAC). At ₹95.20 the diesel line becomes ₹1.37 lakh and the total ₹2.81 lakh.
What typical numbers look like
- Most firms report few outages. In the World Bank's India 2022 Enterprise Survey, 19.9% of firms reported electrical outages, and firms overall averaged 1.3 outages in a typical month (2.1 for medium firms of 20–99 employees, 1.9 for large firms of 100 or more). The calculator's default of 12 cuts a month is a heavy case, closer to a weak feeder than to the national average.
- Average supply hours have risen. The Government of India reports that average supply rose from 12.5 hours a day in rural areas in 2014 to 22.6 hours in 2025, with urban areas at 23.4 hours. These are averages across all consumers, not feeder-level figures for industrial estates.
- Restart losses and DG fuel use. We found no credible public source for typical restart losses or DG fuel use in Indian plants. Both depend on the process and the set. Use your own logs.
What this number does not tell you
- Which cuts hurt. A 2-minute trip in the middle of a moulding cycle may cost more than a 40-minute scheduled cut at lunch. The calculator uses averages; your worst cuts may sit in one shift or one season.
- DG fixed costs. Purchase, servicing, lube oil, batteries and the operator's time are not in the figure. Neither is wear from frequent starts.
- Damage to machines and data. Power cuts can damage drives, controllers, moulds and stored work. Even camera recorders can lose disks; see what to check when an NVR disk fails after a power cut.
- Whether the lost hours could have been sold. As with any downtime figure, the rupee value is real money only on the bottleneck line or when you are sold out. See what one hour of downtime actually costs.
- What a camera cannot see. A camera can show when each machine stopped, when it made the first good part again and how long the restart really took, which is the honest version of the restart-loss input. It cannot read your DG fuel gauge, your feeder's interruption record or the quality of parts made during the restart. Those come from the DG log, the DISCOM and your inspection records.
Related guides
- What One Hour of Downtime Actually Costs an Indian Factory (₹)
- The Real Cost of Factory Downtime (and How to Measure It)
- Idle Machines, Lights and Compressors: The Energy Bill Cameras Can Explain
- Cameras in Injection-Moulding Units: Short Shots, Cycle Drift and Mould Changes
- Changeover time cost calculator
- OEE calculator
FAQ
How do I calculate the cost of power cuts in my factory? Add two parts. Lost production: cuts a month × (uncovered cut minutes + restart minutes) ÷ 60 × line hour rate × 12. Diesel: cuts a month × covered cut minutes ÷ 60 × 12 × litres per hour × diesel price. With the default inputs that is ₹1.44 lakh plus ₹1.30 lakh, or ₹2.74 lakh a year.
Why is the restart loss charged even when the DG covers the cut? Because most lines stop for a moment while the DG starts and picks up the load, then have to restart. If your line truly runs through the changeover, enter a lower restart loss.
Is it cheaper to run the DG or let the line stop? Compare the diesel cost of one DG hour with what one hour of that line is worth. In the example a DG hour costs ₹2,700 in diesel against a ₹1,500 line rate, so covering more cut time raises the total. On a bottleneck line with urgent orders, an hour is worth far more than its cost rate, and the DG pays.
How much diesel does a DG set use per hour? It depends on the set's rating and how loaded it is. Use the manufacturer's fuel consumption chart at your real load, or divide litres filled by hours run from your DG log.
What diesel price should I use? What you pay delivered. For reference, PPAC lists the Delhi retail price at ₹95.20 a litre on 13 October 2026.
Mama reads a factory's existing cameras and each morning tells the owner where machine and line hours were lost the day before. Mama can draw a camera plan for the lines where restarts after a cut take longest. Leave an email or phone in the form below.