I understand that the lights would dim with a dryer or large AC on my own circuit system, but is it normal for that to happen when my neighbor's central AC turns on?

I validated the timing (hearing it from my window and seeing the lights, and it's even when there's nothing else on in the house.

  • 4
    Call the utility, this could be a bad neutral/ground at the transformer, an overloaded transformer, or some other distribution related issue. This is not a DIY problem, so don't go climbing utility poles to try and fix it.
    – Tester101
    Commented Jun 23, 2013 at 12:15
  • 1
    I'm pretty sure that climbing poles would result in a severe fine, even if you knew what you were doing. But if I knew what I was doing up there, I wouldn't have asked the question here!
    – Spencer K
    Commented Jun 23, 2013 at 19:13

1 Answer 1


You and your neighbor may very well be on the same power mains feed. Any heavy current draw on one branch of the circuit will be seen as a voltage droop back up the line toward its source. As that droop passes the point where your mains connection joins in with the neighbor's mains your branch will see a corresponding droop in voltage. This can lead to a dimming of your lights.

This type of voltage droop will always exist in power feed circuits due to the resistance in the wiring. The designer of a power distribution system simply selects wiring sizes with low enough resistance (i.e. fatter sized wire) to keep the droop small enough that it does not create annoying and functional problems with devices attached to the power source. It would appear that in your case the power feed system is not designed with large enough wiring to keep droop to a tolerable level for the loads it is expected to supply. Often the case is that a power distribution network may be designed for a certain size of expected loads. Then later someone comes along and adds heavy duty loads that go way beyond the designed to capacity of the circuits.

  • 1
    I'm going to take the general advice, contact the utility and see where that leads me. They've been pretty responsive when there's no regional emergency. Thanks for the input.
    – Spencer K
    Commented Jun 24, 2013 at 15:40

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