In alternating current power transmission and distribution, complex power is a complex quantity which captures information about both the magnitude and phase of power consumed by a load. It can be defined as the product of the phasor representations of rms voltage and current. Compare to other definitions of power (effective power, apparent power, reactive power). Complex power is usually denoted S and expressed in volt-amperes (not watts), much as apparent power. In fact, apparent power is the magnitude of complex power.