As a retired Electro Mechanical Engineer, I see problems with this so called concept
1. How can altering the sine wave reduce the electrical consumption.
2. Electricity is DRAWN and the nearest outlet which is where they say that you should position the device, MIGHT only might interfere with that particular outlet but what about the others on the ring main.
3. What about other appliances that do not have an outlet, .i.e. Cooker, Shower etc.
The best LEGAL way to save money is to fit out your entire dwelling with LED lighting, turn the television OFF at night, power down your desktop and if you have one power down your laptop and remove the power cord from the charger (fire risk) don’t leave lights burning if you are not using that room yes even if you have LED’s, only fill your kettle for the amount of water you going to use.
PLUS an extra amount to cover the element, after your shower pull the cord and turn it off. Do not leave items on charger overnight (fire risk)
I have been using the above for many many years and I don’t have a “so called energy saving device”