Asking how many kVA = 4kW is almost meaningless.
It is like saying 'I just drove 4 miles. How many miles west did I go?' The question has meaning if you supply additional information.
In an AC circuit, both the voltage and the current continuously cycle from 0 to + to 0 to - and back again. The current will change at the same frequency as the voltage, but does not need to be perfectly in step with the voltage. However the _real power_ delivered to the load depends upon that portion of the current flowing that is exactly in step with the applied voltage. kVA is the raw product of voltage and current; kW is the real power delivered to the load. kW and kVA are equal if the voltage and current are perfectly in step.
kVA and kW are related by the 'power factor' of the load. kVA = kW/pf
When pf=1.0, then kVA = kW.
pf can never be greater than 1.0 .
Most (but not all) loads have pf > 0.7. So as a reasonable _guess_ you can say 'kVA will certainly be greater than or equal to kW, and probably be less than kW * 1.4 '
Some inductive loads can have pf that approaches 0, so without knowing the load pf, you can never be sure.
-Jon
