Anything is possible but let's remember, the OP asked about ONE subwoofer and the cost savings. Not the guy in your town who has jammed an entire IMAX theater into his basement and had to have his electric panel upgraded to support his drain of the grid. I don't see anything in the manaul for that particuar sub that says anything about a standby mode, so if it's on all the time, yeah, maybe a couple of bucks a month. If it has some undocumented standyby mode, a buck a year. If it has no standby mode though, I'd turn it off. Of course, I'm in AZ where I think about my two 5 ton A/C units cooling electrical crap that's left on all the time more than the power the unit uses.
Edited by emesnik - 10/20/12 at 2:02pm