Power usage is most efficient when the power factor is near one. It costs the utility more in wire and in losses when the power factor is low. The power factor is dragged down by motors and raised by capacitors. The thing is that if the power factor is raised too high, it goes backward - or leading. This is a bad thing. Various electronic devices and metering can become confused. The power factor does not stay the same in any facility. Motors turn on and off. So, the capacitors have to be either automatic - very expensive - or they have to be sized conservatively. Capacitors take up room, they get hot and they age.
There are certain power quality advantages to capacitors including some TVSS benefit. But, as has been mentioned, there aren't a lot of motors in the average home (fan motors for residential loads are small and don't use a lot of power) and the utility doesn't tend to charge homes for KVA. Though I have seen at least one case where they do. And this should be the only example of saving utility charges. I wonder if other changes were made at the same time for those of you who saved money - like an energy efficient furnace being installed. The capacitor changes the KVA, not the KW. A power factor of one means that the two are the same. Which means that utility losses are minimized. If the utility isn't charging you for potential losses, which they usually don't for residential users, then you aren't going to save money because your usage, or KW charges, are the same. You have to really understand your bill to determine if they are charging you for KVA.
I've tried to express everything with less lingo, don't know if that was helpful or not. Debbie
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