Real, reactive and apparent power (PQS)
Real power, also known as active power (P) is consumed by resistive loads. Reactive power (Q) is either consumed by inductive loads or generated by capacitive loads.
Apparent power (S) is the capacity of your measured power system to provide real and reactive power.
The units for power are watts (W or kW) for real power P, vars (VAR or kVAR) for reactive power Q, and volt-amps (VA or kVA) for apparent power S.
Positive real power P(+) flows from the power source to the load. Negative real power P(-) flows from the load to the power source.