Volt-amp reactive (VAR)
While power is measured in watts, if there’s a phase difference between voltage and current, which causes a power factor less than 1, then you need a way to indicate the difference between real power and reactive power. Watts are volts times amps, but if they’re out of phase, we keep the notation volt-amps or volt-amp reactive (VARs) to indicate the total of real and non-real power.
In electric power transmission and distribution, volt-ampere reactive (var) is a unit of measurement of reactive power. Reactive power exists in an AC circuit when the current and voltage are not in phase. The term var was proposed by the Romanian electrical engineer Constantin Budeanu and introduced in 1930 by the IEC in Stockholm, which has adopted it as the unit for reactive power.
Special instruments called varmeters are available to measure the reactive power in a circuit.
The unit "var" is allowed by the International System of Units (SI) even though the unit var is representative of a form of power. SI allows one to specify units to indicate common sense physical considerations. Per EU directive 80/181/EEC (the "metric directive"), the correct symbol is lower-case "var", although the spellings "Var" and "VAr" are commonly seen, and "VAR" is widely used throughout the power industry.