(M. W. - United Kingdom)
A system with a value of PF=1 (power factor of unity) is a system that draws from the AC supply line only the exact amount of power it needs to perform its function. This means that systems with a PF of less than 1 draw more power than is theoretically needed for the purpose in hand. (For example a system with PF=0.65 draws about 54% more power than is theoretically necessary.) This extra power is transformed into reactive power and returned to the grid.