Off topic slightly; but why do some neighborhoods have significant power fluctuations and some don't?
My voltage is consistently in the 119 - 123 range whenever I've logged it, yet a friend in another sub-division just down the street has frequent fluctuation, dropping into the 115 - 121 range.
The distance from transformer vs size of the transmission cables, size vs load on the outside transformer, size vs load on the substation, power factor, wiring size/length and other loads inside your house, etc. Exactly like asking why your city water pressure is different at the sink than somebody two blocks over when you both get fed pressure from the same water tower.
Here in Indiana, the utilities are only required to keep voltage within 5% of 120v (+- 6) in urban and suburban areas, 6% of 120 in rural. In the summer, the local peak load is so much larger than the median load, we would need a seriously expensive overbuild to do much better.
