Best bet is to simply see what your energy savings would be. I imagine in FL you're gonna end up spending quite a bit on A/C in the summer, and those costs could add up.
I also have read previously one of Dan's Data Letters when he mentioned that on average the real power-user of any pc is the monitor. Simply turn that off when you're away and you can cut a lot of the power being used, but still allow the pc to Seti or whatever else.
There *are* some slight issues known with turning it off and on frequently. Most apply to older, online-forever machines though... such as a lot of servers having hard-drive crashes when powered down and then back up for Y2k.
Really, I just leave it on, turn the monitor off and forget about it.