One thing to remember with anything that has THD is it only applies to audiophiles and power company managers. No one cares if their light bulb is a little bit dimmer than it is supposed to be or that your hairdrier could be more efficient if they put the most basic power reducing circuit instead of just one diode to block 1/2 of the sine wave.
The take home message is that after your dirty power component sucks out the small amount of the 60 Hz sine wave it needs what is left behind is a distorted non sine wave (dirty power). What is left behind in your lines plus the fresh supply of the good power coming from the generator is what your audio equipment gets. How far does the dirty power what is left over get? Theoretically it goes back into the grid where it gets averaged back in to everyone. But in reality it is worse the closer you get to the source. That is why people get dedicated power lines for audio but still claim they can hear when a neighbor is running a hairdrier down the street.
The take home message is that after your dirty power component sucks out the small amount of the 60 Hz sine wave it needs what is left behind is a distorted non sine wave (dirty power). What is left behind in your lines plus the fresh supply of the good power coming from the generator is what your audio equipment gets. How far does the dirty power what is left over get? Theoretically it goes back into the grid where it gets averaged back in to everyone. But in reality it is worse the closer you get to the source. That is why people get dedicated power lines for audio but still claim they can hear when a neighbor is running a hairdrier down the street.