Power regeneration - good idea? PS audio?

Is there that much of a difference between 117 V and 121 V coming through your system?

That's about what my variation is throughout the day

I think it would be interesting to measure the distortion level at my home. Can anyone recommend a meter for this?

A good multimeter like a Fluke 789, but I bet there are cheaper ones.

Is there that much of a difference between 117 V and 121 V coming through your system?

I've seen a 3 volt change like that rob an amp of 40 watts of power. But a conditioner does more than that- a good one will provide a clean AC waveform, thus allowing the power supplies in audio equipment to operated as designed.

"I've seen a 3 volt change like that rob an amp of 40 watts of power. "

An amplifier would have to be deficient, defective, or broken for this claim and  assertion to be accurate.