Real power is the actual amount of power being used or dissipated in an AC electric circuit, measured in watts (symbolized by the capital letter P) . It is also known as true power or active power, and its function is to do useful work in an electric circuit. Reactive power, on the other hand, is a function of a circuits reactance (X) and does not directly electrify items, but still plays a role in keeping electricity moving evenly between generators and capacitors. It is measured in volt-ampere reactive (VAR) or kVAR. Apparent power is the vector sum of real and reactive power, and it represents two types of power: the real type that has been sent out to power up items and the reactive one that remains within the AC circuit. It is measured in volt-ampere (VA) or kVA. The combination of reactive power and true power is called apparent power, and it is the product of a circuits voltage and current, without reference to phase angle.