Watts to kVA calculation formula
S(kVA) = P(W) / (1000 × PF)
The apparent power S in kilovolt-amps (kVA) is equal to the real power P in watts (W), divided by 1000, multiplied by the power factor PF.
kVA = W / (1000 × PF)
kilovolt-amp = watt / (1000 × PF)
Power (P) = 350W
PF = 0,7
Apparent power (S) = 350W / (1000 x 0,7) = 0,5kVA