As my system has become more hi-fi it seems to have mostly overruled vagaries in the electric grid. I used to specify late night listening for maximum music, but now I often find that even high demand periods like dinner time can sound very good everything else be damned.
Still though it is true that the midnight hour and thereabouts has poured out the most memorable musical sessions. There are times though such as Thanksgiving eve when nearly every household is up late preparing THE DINNER for the next day, and that seems to do something to the grid that is semi-tragic for musical reproduction.