Suppose I have a non-linear load in my home (A half wave rectifier supplied DC load, say). Since it will consume current from the source only during +ve cycle of the Voltage, the current will be half-wave too. The current isn't sinusoidal. We can mathematically say that Distored Current = Algebraic Sum of Various Sine Wave currents with various Frequencies. Which we call the Fourier Analysis. But where can we apply this? I don't think we can say, Power Consumed By load = Sum of (Irms ^ 2 ) * R of all sine wave components. (This we can't do because, superposition principle don't work when we square the quantity) We can however do, Poser Consumed by load = Sum of (Vsource rms * Irms * Cos(phi)) of all sine wave components. (Because superposition holds here, because the current isn't squared) Now, How can this harmonic analysis aid me in finding the losses in the source and cables. For the same reason, I don't think we can say, Power lost in source and cable = Sum of (Irms ^ 2)* (Resistance of source+cable) for all sine wave components. How do we find the losses then? To summarize, Two load current waveforms can have same RMS value, but one with lots of harmonics and other with very less harmonics. From the point of minimizing the losses in source and cables, which one would be better. Why and how?