About every nine months this sort of device comes around, repackaged but with the same extravagant promises.
It's pure, dishonest, BS.
These things do nothing a 30 cent capacitor can't do, and are completely useless in a residential setting. You just don't have enough motors starting up for them to matter. Because that's all they can do: correct the power factor of a cheap motor.
Open one up, and what do you find? A capacitor ... with, perhaps, some other things added on for marketing glitz ... an 'on' switch, an LED, etc.
Nor does it make one whit of difference where in the system this snake oil is applied ... at the panel, plugged into a receptacle, attached to the appliance. Save your money - and give these persistant high-pressure sales folks the deep six!