Active power

Active power P is an apparent power component and refers to the power that can actually be converted into other forms of energy by the consumer. It is described in the unit Watt (W). Thus, for purely resistive loads such as a resistor, it corresponds to the apparent power. Then there is no phase shift between voltage and current: φ = 0.

Capacitive and inductive components of the load cause a deviation of the active power from the apparent power: reactive power is generated by the phase shift between current and voltage.