Power regeneration - good idea? PS audio?

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.

And today through the snow falling I saw a monkey fly, upside down.

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

Sagging voltage can reduce peak power output from an amplifier. I’ve also  encounterd distribution networks that are so stiff that they damage mechanical equipment.