It's behind a paywall, but the gist of it is that so many bad power supplies are being connected to the grid that the sine waves are getting distorted. It's based on this research from Whisker Labs[1].<p>Better power supplies can help with the distortion, but it really shouldn't matter much, except in extreme cases where things are at 99% of their limits in the power grid, on a hot day.<p>By the way, you can learn interesting things from analysis of the power grid. Long ago I remember a Slashdot comment about using it with covertly gathered recordings estimate the effective yield of nuclear enrichment operations in the middle east. <i>I've been trying to find that thread but Google isn't what it used to be</i><p>[1] <a href="https://www.whiskerlabs.com/analysis-of-total-harmonic-distortion-on-the-us-electric-grid/" rel="nofollow">https://www.whiskerlabs.com/analysis-of-total-harmonic-disto...</a>