Where P is the real power(or average power) and Q is the reactive power
If V and I are the rms or effective voltage and current phasors represented in complex form.
The complex power 'S' is defined as the product of V and conjugate of I
I* is the conjugate of I.
S is a complex number the real part (P) is the real or average power and the imaginary part (Q) is the reactive power.
φ is the phase angle.