# Thread: Generator Rating Question

1. ## Generator Rating Question

Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

If some one can explain please..

Thanks

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Originally Posted by Sajid khan
Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

If some one can explain please..

Thanks

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Most generators I have seen large and small are rated in both KVA and KW.

3. All generators are rated in both kW and kVA.

Sometimes depending on the load, one will be more of a critical threshold than the other. Whichever you hit first is the limit.

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Originally Posted by Sajid khan
Why the bigger generators are rated in kW instead of KVA rating. E.g i have seen 2500kW rating for both gas gensets and diesel gensets.

If some one can explain please..

Thanks

Sent from my GT-I9300I using Tapatalk
As already mentioned, the genset will have both a KW and KVA rating. The KVA rating will tell you how much current it can handle. The KW rating tells you how much power it will deliver. With a genset this is critical info as the KVA relates to the generator current capacity and the prime mover relates to the power it can deliver (KW). As an extreme example, a genset rated 100 KVA @ .5 PF will only have enough engine to provide 50 KW.

5. I like to think of it like this; kW is the rating of the engine, kVA is the rating of the alternator.

Because the kW rating is typically 80% of the kVA, it means the engine can't produce enough energy to overload the alternator as long as the load power factor is above 80%.

6. Standard application is based on 0.8 PF. If the actual PF is higher, you may get more out of the generator, which is why you must size this way. We donâ€™t typically design beyond the rating for capacity...so using kW. This also helps concerns for elevation derates if they apply as conservative.

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