My main question: Both legs of my home power are varying by a few tenths of a volt. For example in 20 seconds, I am seeing it move up and down randomly between 121.1 volts and 121.7 bolts. This is with no major appliances or electrical loads on the system. I am seeing this at the main lines on the breaker box, and at electrical outlets.
The larger story:
I've recently had much bigger varances, like momentary drops down to 90 volts, and longer spans of time between 110 and 120 volts. I know that is not normal, so there is a problem somewhere.
I called the power company, had a lineman come out, and he said the likely problem is my old underground power wires that serve the house. I plan to get those replaced because they're 55 years old and it's a somewhat short run.
However my first question is about a variance of a few tenths of a volt. Is that normal?