Assume a single-phase AC voltage applied to a series circuit with a certain impedance. Because of the real and imaginary part of the impedance, we get both real and reactive power. Now, if we were to connect a capacitor in parallel with the circuit, and if this capacitor supplies a certain amount of vars, what happens to the total reactive power of the circuit? My intuition tells me that: P(total) is unchanged because the capacitor is purely reactive. Q(total) = Q(source_before) = Q(source) + Q(cap) So basically by adding that capacitor, you're reducing the the reactive power supplied by the voltage source, and thus increasing the power factor. Am I right?