In order to fully understand the concept of power in electric generators, it is necessary to understand the following three concepts, apparent power C expressed in KVA, active power P expressed in kW and reactive power Q expressed in kVAr.
Where, therefore, P is, active power, power that performs useful work. It represents most of the apparent power and is spent on supplying active consumers, purely reactive loads (consumers).
Q is reactive power, power that is used to cover various losses within the unit, but also to supply energy to reactive consumers (magnetization of magnetic circuits of individual devices, fluorescent lighting, asynchronous motors, voltage regulation on transformers, etc.).
S is the apparent power, so to speak, the total power generated by our generator. It has both active and reactive components, thus covering both active and reactive reactive energy consumption. The power factor, cos φ, represents the ratio of active power and apparent power, cosφ = P / S.
Analogous to this explanation, we will observe a mug of beer from the picture below. When we order a mug of beer at the bar, we get the following, a mug with a volume of 0.5 l. This volume is analogous to the power S, we asked for 0.5 l and we got it. Inside the mug there is a liquid part, a part that serves for our enjoyment and refreshment, as well as for our consumers. This is the part of energy that we as consumers directly feel and enjoy. Finally, to the top of the mug, there is foam, it is there to fill the mug completely, in the case of a generator it is Q, it covers losses due to electricity transmission, magnetizes transformers to maintain a constant voltage. So, energy that we cannot directly feel, but it certainly exists and has its purpose, fulfilling our electrical needs, just like the foam that fills a mug.