Brian Gaff explained :
I'm not sure exactly what you are doing here?

It is one of those silly scam gadgets, which claims to save on your
electricity bill. They reduce the voltage by 10% and claim it will save
you 10% on your bill, which is absolute balony. Heating loads will just
take that 10% longer, motors produce less power output, incandescent
lights will be much less than 10% dimmer, LED's and CFL's will simply
draw more current, to produce the same amount of light, or more lights
will be needed to make up for the darkness.

The unit itself, will also waste some power in heat produced.