What does unity power factor UPF mean?

Unity power factor has a value of 1.0. This means the current and voltage waveforms are in phase. This is only possible if the net load is non-reactive (resistive). If the load is either capacitively or inductively reactive, the power factor will be other than unity. If an inductively reactive load such as a motor is offset by a capacitively reactive load such as a PF correction capacitor, it is possible to acheive a net load that has unity power factor. Some loads, such as resistance heaters, are intrinsically non-reactive, and present a unity power factor.