Power factor (cos φ )
The power factor - cos φ - is a measure of the use of electrical energy (active power) by a device relative to the energy supplied to it (apparent power). If any component of the circuit has this coefficient less than one, then we start dealing with energy that has been consumed but not used (reactive power), which is converted into adverse phenomena, such as overheating of wires, etc. For the domestic user, the power factor is irrelevant, since he pays anyway for the energy actually used, i.e. active power. But industrial consumers already have to prevent reactive power or compensate it accordingly.
P - active power, S - apparent (combined) power