5To review, the power factor of an AC circuit is the cosine of the phase angle between total (source) voltage and total (source) current. Power factor represents how much of the line current goes toward doing useful work. Reactive loads do not transform electrical energy into work, but rather alternately store and release electrical energy. Current at a purely reactive load, therefore, is not as useful as current at a purely resistive load. However, reactive current still “occupies” ampacity on a power line, and so the existence of a low power factor means the system is not delivering as much power as it could.