Generator Runtime from Grid Outage Calculator
Grid down for hours a day? See how long the DG must run.
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Your results
Generator Runtime from Grid Outage Calculator by TheCalcTools
How the Generator Runtime from Grid Outage Calculator works
Enter total outage hours per day, how many separate outages happen, and the battery backup time per outage.
The DG runs for whatever the batteries cannot cover.
Fuel is DG hours × site kW × litres per kWh.
The formula
Worked example
Using the default values shown in the calculator:
| Grid outage per day (hours) | 10 |
|---|---|
| Battery backup time (hours) | 3 |
| Outage events per day | 3 |
| Site load (kW) | 4 |
| Genset consumption (litres per kWh) | 0.32 |
| Diesel price (PKR per litre) | Rs275 |
| Days | 30 |
- DG hours = 10 − 3 × 3 = 1.0 h a day.
- Diesel = 1 × 4 × 0.32 = 1.3 L a day, 38 L a month, costing $10,560.
Result:
| Generator hours per day | 1.0 |
|---|---|
| Diesel per day (litres) | 1.3 |
| Diesel over the period (litres) | 38 |
| Diesel cost over the period (PKR) | Rs 10,560 |
| Energy from batteries per day (kWh) | 36.0 |
Frequently asked questions
Why does the number of outages matter?
Each outage starts with a full battery only if there was enough time to recharge. This tool assumes the batteries recharge fully between events.
Does this include battery recharge energy?
No. After an outage the rectifiers recharge the batteries from the grid, so battery energy is not free; it is shifted to the grid.
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.