kVA is apparent power, the total electrical load a supply must carry. kW is real power, the part that does useful work. They are linked by the power factor: kW equals kVA multiplied by power factor. A generator rated at 100 kVA with a power factor of 0.8 delivers 80 kW.
For a genset buyer, this is the first check, since a quote in kVA and a load in kW are not the same unit.
Why are there two units?
In alternating current, voltage and current do not always peak together. Motors, transformers and fluorescent lights store energy in magnetic fields and give some of it back, so part of the current does no useful work. Power factor is the ratio between the useful part and the total.
A heater has a power factor near one, so kW and kVA are almost the same. A loaded induction motor may have a power factor of 0.8 or lower. The alternator must still supply the full current, so it is rated in kVA.
How do you convert between them?
Use two simple relations:
- kW equals kVA multiplied by the power factor.
- kVA equals kW divided by the power factor.
How does this affect choosing a generator?
Add up the real power of everything you will run, in kW. Divide by your power factor to get kVA, and allow headroom. Most generator sets are rated at 0.8 power factor, so a load of 40 kW needs about 50 kVA before any margin.
Then allow for starting current. Motors can draw several times their running current for a moment when they start, and a generator that is too small will stall or drop voltage. Ask the maker how much starting load the set can take. See genset kVA ranges for the sizes made in Gujarat.
Check also whether the rating is standby, prime or continuous. The same machine has a lower output rating for continuous use than for standby, and the quote must say which one it is.
Altitude and temperature also reduce output. A set that delivers its rating at sea level in cool air delivers less in a hot, high location, so give the maker your site conditions when you ask for a quote.
Finally, do not size to the exact load. Leave margin for future equipment, but avoid a set far too large, because a lightly loaded diesel engine runs poorly and can wear faster.
What should the quote and datasheet say?
Insist on seeing the rating basis, the power factor, the voltage, the frequency and the phase. Ask for the engine power as well, since the engine, not only the alternator, limits what the set can deliver. A genset with a large alternator and a small engine will not give the stated output.
Our overview of gensets made in Gujarat explains how engine and alternator are matched, and the load test is the way to prove a rating before shipment.
Next step
Send us your load list and supply details, and we will find genset makers that fit, then witness the load test. To start, book a free sourcing review.