<P> The VA and var are non-SI units mathematically identical to the watt, but are used in engineering practice instead of the watt to state what quantity is being expressed . The SI explicitly disallows using units for this purpose or as the only source of information about a physical quantity as used . </P> <P> The power factor is defined as the ratio of real power to apparent power . As power is transferred along a transmission line, it does not consist purely of real power that can do work once transferred to the load, but rather consists of a combination of real and reactive power, called apparent power . The power factor describes the amount of real power transmitted along a transmission line relative to the total apparent power flowing in the line . </P> <P> One can relate the various components of AC power by using the power triangle in vector space . Real power extends horizontally in the î direction as it represents a purely real component of AC power . Reactive power extends in the direction of ĵ as it represents a purely imaginary component of AC power . Complex power (and its magnitude, Apparent power) represents a combination of both real and reactive power, and therefore can be calculated by using the vector sum of these two components . We can conclude that the mathematical relationship between these components is: </P> <Dl> <Dd> S = P + j Q S 2 = P 2 + Q 2 S = P 2 + Q 2 cos ⁡ θ, power factor = P, real power S, apparent power (\ displaystyle (\ begin (aligned) S& = P + jQ \ \ S ^ (2) & = P ^ (2) + Q ^ (2) \ \ (3pt) S & = (\ sqrt (P ^ (2) + Q ^ (2))) \ \ \ cos \ theta (\ text (, power factor)) & = (\ frac (P (\ text (, real power))) (S (\ text (, apparent power)))) \ end (aligned))) </Dd> </Dl>

What is the si unit of power factor