I'm far from being an expert on electricity - in fact, I'm just a pilot...
But this is the way I understood it:
Watts=(Volt x Amps) x power factor
REAL Power: Watts
APPARANT Power: VA
A three-phase generator has a "Power factor" (cos phi) of 0.8 - so as "catchup" said the (k)VA is always higher.
Hopefully someone can explain it better!