Large voltage swing on incoming main hot line- definitely outside?

Question

So for much of last fall, I had an issue of flickering lights in my house (half of the house seemed to flicker in unison). Back in December, I called the electric company, who came out, and claimed they found and tightened "a slightly loose neutral" in one of their connections outside, but thought it wasn't the issue (he said there was no charring, and thus there had been no arcing). So after they left the flickering lights went away. Problem solved...

Until last night, when our lights started flickering like crazy (I mean to the point of almost going off). So this morning, I opened up my main breaker box, to see what I could discover. It turns out that when the lights are flickering, one of the two hot lines is having a pretty wild voltage fluctuation (I measured the voltage from the incoming neutral to each of the two incoming hot lines. One hot line stayed rock steady at 119 volts, the other varied by 15-20 volts when the lights were flickering- dropping to 100-105 volts).

Now, this measurement was done on the incoming side of my main breaker (i.e.- I was measuring the hot lines coming in from my meter).

My question is- since I am measuring the hot line dropping in voltage on the incoming side of my breaker box, does this indicate that it is not something inside my house that is causing the fluctuation? Or could something in my house be causing the kind of extreme voltage draw that I am seeing?

Answer 1

Definitely outside, in your meter box or with the utility lines feeding your box. Call them again, now!!! Btw, the meter is theirs also.

Answer 2

Almost positive it's outside, but if you want to eliminate any chance it's inside, then trip all the breakers on that hot and measure it again. Personally, I wouldn't bother double checking, since the problem outside could be serious (sounds like a connection is arcing to me). Get the utility company out there.