power factor signifies the amount of power that is consumed(active power) and reflected(reactive power).
Loads with some capacitive/inductive behavior dissipate some of the energy as active power and store the other and return it back to the source as a reactive power.
active power -> P = V X I X pf, pf = cos(phase angle)
a higher power factor of 1 unit will consume all the energy delivered to it while a unit with pf of 0.7 will return some electrical energy to the system, causing distortions on the supplied current and voltage.
The 30% is not necessarily lost, rather returned to the source, but because it creates distortion, it increases the loss on the supply line, transformer....