This product is being advertised on a German internet sites with lots of glowing tributes;
https://getvoltplug.com/article/de?gclid=EAIaIQobChMIuJTr_d7m-QIVJUblCh1xbA8kEAEYASAAEgKOTPD_BwE
A translated section reads ; "Called VoltPlug, its technology was originally developed by none other than legendary Serbian-American inventor, electrical engineer, mechanical engineer, and futurist Nikola Tesla.
At first it was hidden from the general public because it offered average families an opportunity to save on their monthly energy bills. VoltPlug is a small, compact, affordable, and easy-to-use plug- in device that prevents unnecessary current from entering electrical wiring and overloading the network.
VoltPlug is your electric utility's worst nightmare. They tried to hide VoltPlug from the common consumer and even banned it in retail stores.
The big energy companies feel threatened by this device and its potential to erode their profits.
But thanks to the Internet, the secret has been revealed and everyday life now benefits from lower electricity consumption overall and also in household appliances."
Does anyone understand the principle, could it be a viable idea? If it comes up in German & you are interested, you can use Google translate