I would have to say in my case that X10 has increased my electric bill. Now being able to control or have the computer control lights and other stuff, I find that before where lights were left off all night,they are coming on and going off with the control of X10. Hall way lights are on and dimmed giving me some light when I'm ready for bed. Before they were off and I just found my way in the dark.
The trade off is a safe more secure environment inside and out. X10 has helped me light up the night were as before it was always dark. A few bucks more on the electric bill but X10 helps to control that to. ;D
(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)---(http://www.bdshost.com/X10/lpup.gif)----KDR