Most loads in modern electrical distribution systems are inductive. Inductive loads need an electromagnetic field to operate. Examples include motors, transformers, gaseous tube lighting ballasts and induction furnaces.
Inductive loads require two forms of power: Working power (expressed in kW) to perform the actual work of creating heat, light, motion, machine output, etc., and reactive power (kVAR) to sustain the electromagnetic field.
Working power consumes watts and can be read on a wattmeter. It is measured in kilowatts (kW). Reactive power doesn't perform useful "work," 
but creates the electromagnetic fields associated with the production of work in motors. It places a heavier drain on the power source, as well as on the power source's distribution system. Reactive power is measured in kilovolt-amperes-reactive (kVAR).
Working power and reactive power together make up apparent power which is measured in kilovolt-amperes (kVA).
The "right power triangle" shown here is often used to illustrate the relationship between kW, kVAR and kVA.
