Years ago, even though I knew better, I bought one of the Green Plugs
mostly out of curiosity.  I have a watt-hour meter that I used to
measure a day's worth of power consumption from my freezer without the
Green Plug.  Then I tried again with the Green Plug between the freezer
and the watt-hour meter.  Surprise, surprise, the consumption was
greater with the Green Plug in place, and by more than just a few
percent.

I took it apart, and saw what looked like a triac clamped to a heat sink,
plus some other circuitry.  I think this was a scam.  I bet they shaved
a few watts off a purely resistive load like a light bulb, making their
demonstration watt-hour meter run slower, but clearly they did not
achieve any positive results with a modern induction motor.

Steve McCollum