Watts and kilovolt-amps (kVA) are both measures of power. Watts measure real power while kVA measures apparent power.

In most cases, there will be some amount of apparent power that does no real work and is thus not real power. This is represented by the power factor, which is a measure of the efficiency of the circuit.

The apparent power S in kilovolt-amps (kVA) is equal to the real power P in watts (W), divided by 1000 times the power factor PF:

S_(kVA) =  P_(W) / (1000 × PF)