A diesel generator is a long-term capital purchase. Sizing and specifying it correctly up front prevents underperformance, excessive wear, and costly upgrades later.
1. kW vs kVA and power factor
Generators are rated in kVA, but your loads are in kW. The relationship is kW = kVA × power factor. For most industrial loads, assume a power factor of 0.8. A 100 kVA generator delivers about 80 kW at 0.8 pf.
2. Standby vs prime vs continuous
- Standby — runs only during outages, no overload. Sized for emergency backup.
- Prime — runs continuously with variable load, allows 10% overload for 1 hour in 12. The most common rating for industrial sites.
- Continuous — runs at a constant load 24/7, no overload. For base-load or off-grid power.
Choose the rating that matches how you will actually use the generator.
3. Size to your load — with margin
Add up your running loads, then add the largest motor starting current (motors draw 3–6× rated current on start). Size the generator so the voltage dip during motor start stays within acceptable limits — typically 15%. A common rule: generator kVA should be at least 1.5× your running load for mixed loads, more for large motor starting.
4. Fuel and runtime
Diesel is standard. Decide on the tank size for your required runtime between refuels — a base tank may run 8–12 hours; a bulk tank can run days. For remote sites, larger fuel storage means fewer deliveries.
5. Enclosure and environment
- Sound-attenuated enclosure — reduces noise to acceptable levels for sites near occupied areas. Essential for urban and hospital use.
- Weatherproof enclosure — for outdoor installation.
- Canopy vs container — small generators use a canopy; large industrial sets may be containerized for transport and security.
6. Alternator and voltage
Match the alternator to your site voltage and frequency (e.g., 480V/60Hz or 400V/50Hz). If you will export, confirm the destination country's standard.
7. Control system
A modern controller monitors voltage, current, frequency, oil pressure, coolant temperature, and fuel level, and supports remote monitoring. For critical sites, remote monitoring and auto-mains-failure (AMF) are essential.
Request a quote
Tell IGC your required kW, voltage, frequency, runtime, and whether you need a sound-attenuated enclosure. We will recommend the right diesel generator set.