PFI Plant capacitors are connected to a circuit that operates at a nominally lagging power factor, the extent that the circuit lags is reduced proportionately to the amount the capacitors lead. Circuits having no resultant leading or lagging component are said to operate at a unity power factor – where the total energy consumed is equal to the usual energy. Most commercial electricity users are also subjected to an additional charge for reactive energy – generally referred to as an “availability” charge. Reactive energy is effectively the power used to energize the magnetic fields in motors, inductive heaters and so on. While the useful energy is measured in kilowatts (kW), the reactive part is measured in kilovoltampsreactive (kVAr). It is the aim when specifying and installing power factor correction equipment to reduce the reactive energy drawn from the system.