How do these Power savers work?

[VidPro]

Have you seen these devices that claim to "reduce your power bill" , you put them on the wall plug close to the box, or put this entier house box integrated into the fuse box. some of them are (suppedly) just capacitors
the devices ONLY reduce the meter spinning when using a "induction" motor.

i have applied one, and went out and did the usual stopwatching the utility meter, and well it worked, freaky like, but i only saw any visual reduction in meter movement, from induction motor running.

the unit Said it "uses no power" but i tested and there does seem to be some consumption from the unit, that is quickly offset when any single induction motor is working, this particular unit is small and digital like. and really didnt cost more than it saved in 2 months , BECAUSE were running induction motor fans as AC at night.

when hooked up in parellel with an induction motor, i cant determine ANY slowdown from the induction motor, but just like the utitlity meter outside, my own amp metering went down. if meters are FLawed , is the meter the utility company is using flawed the same way?

should induction motors have caps on them? i saw some info on fans that said something about split capacitor? what is that?
Small motors on expencive junk even i rarely see any caps added, but the big modo motors have starting caps.

what other power device at all could possibly benifit from capacitors on the power? switching power supplies? computers, florescent ? because i dont see Anything changing except induction motors , but some stuff is to small to test a utility meters reaction.

 

[lctorana]

If you are billed by the kWh, then power factor correction will make zero difference to your bill.

Some industrial users (e.g. data centres) are billed by the kVA-h, and are responsible for their own power factor correction.

Apart from power factor correction, and perhaps waveform cleanup, I can't imagine any other tangible effect a device could have.

 

[VidPro]

I am billed by a human comming out and reading the meter item on the side of the house. the same meter item i am able to see myself.
it has that old spinning disk thing on it with the markings, and little slowly spining . . .http://www.cosjwt.com/blog/wp-content/uploads/2008/08/mymeter.jpg there like that thing.
whatever KWH for the month it says, is what i pay, real or not.