[Jager]

While it's true that THD will increase with distance from the utility or generator interface (Point of Common Coupling, or PCC), because of voltage sag; and while it's also true that the practical effect of poor THD will vary depending upon the current demand of a load (smaller loads generally being affected less), I'm not sure the dirty pond metaphor is very apt. Plug in a load and the source of the electrons traversing the circuit powering that load come from the utility interface (or generator)... not a mishmash of electrons from throughout the house wiring.

If the dirty pond analogy were accurate, the entire grid would have very poor THD as all those homes and businesses polluted the bigger pond. Fortunately, it doesn't quite work that way. Utilities typically provide grid power with a THD of 5% or less.

People can do whatever they want, of course. But make no mistake... THD is a thing. Part of the problem is that generators have been around for many decades and most of our individual experiences with them is that they "just work." And they usually work just fine for a very long time. But most of the loads that we collectively powered with those generators for all those years were linear loads. And linear loads aren't generally affected by high THD.

Nowadays we have a proliferation of non-linear loads. And non-linear loads are very much affected by high THD.