I got a Monster Power conditioner with a VU meter whcih reads close to what my multimeter sees for house voltage. For fun, I started watching the voltage and was suprised how much it changes. I live in No. CA (bay area). My normal voltage in the early evening is 121 - 122v. I've seen it move between 115v and 123 or 124v depending on the day and time of day. Late evening / early morning (like 2AM), I've seen it to 115v. I have no idea why it would drop unless there was some power plant maintenance. During the heat wave it touched 109v. So in my case, I would assume my norm was 122v and the nominal range would be 115 - 125. Of course, PG&E sometimes delivers "0"v but then you can't play the stereo anyway.