unplug imac when not in use?

Doesn't matter at all.

 

You need to find out if the Mac has an internal backup battery. If it does, then unplugging it will eat up the battery, and it will die prematurely. Then, everytime you boot up, you will get an error message about the computer not being set to the correct date, at least until it connects to the network and gets the correct time.

 

On page 15 of the owners manual Apple recommends:

Putting Your iMac to Sleep

If you‘ll be away from your iMac for less than a few days, put it to sleep. When your iMac is in sleep, its screen is dark. You can quickly wake your iMac and bypass the startup process.

I have followed these directions to the the letter, in 4 years my computer has been 100% reliable.

 

I don't know enough to say if it's bad or not, but I guess my question would be, why? I don't think a battery backup is necessary unless you are always doing some sort of urgent important work on your iMac that in the event of a power outage you can't possibly use. IMO, a good surge protector is more than enough. I know in the "surge protector" thread many are recommended pricey back up solutions, but in all my years of computing i've never had a power surge damage my computer and I generally use consumer oriented surge protectors like Belkin.

 

A surge protector is great for protection against the voltage going up over a threshold but offers no protection against brownouts. The power grid in my city is sometimes unreliable and experiencing brownouts. Only a UPS can prevent these. It can also allow your computer to shutdown gracefully while not corrupting data in case of a prolonged power failure, which is always great .

To come back to the original subject, I would add that sleep mode is a low power mode and unplugging your Mac is essentially a no power mode. This way you save energy and if you took time to shut it down in the OS, your only saving power and waiting longer for it to come alive.

 

I leave my desktop on and usually awake even if I'm not using it because I like it to be available for streaming media to my stereo. However, if I go out of town, I shut down and unplug it. I do have a good surge protector, but I figure if something did go haywire (lightning or otherwise) it's safest to have it totally disconnected.

Note that if you're worried about this you should unplug any Ethernet cables and connections to USB devices with separate power supplies (or unplug their power supplies too -- I just unplug my surge protector and that takes care of everything). Lightning can come in through your cable/DSL line and propagate to everything physically connected to your router; it can also come in through anything plugged into the wall. So think about your chain of devices and, if you're going to bother doing this in case of storms, extended absence, or whatnot, make sure you unplug everything in the chain.

Starting up is one of the biggest stresses you can put on your hard drive, so if you're concerned about longevity, shutting down, unplugging, plugging in, and restarting every day probably isn't the best idea. On the other hand, it's not so much of a stress that an *otherwise* healthy drive will fail because of this. It may bring existing problems to light more quickly, though.

 

it wont hurt it but an easier thing to do would be to get one of those power supplies with an auto shut off or a remote to save power.

heres a link to one http://www.amazon.com/Belkin-BM106000-06-6-Outlet-Surgemaster-Protector/dp/B002XDK7AU

 

I still think from personal experience it is not necessary for the average user. We have brown outs and rolling blackouts (due to 100+ degree heat), and my computers have been abruptly powered down because of them, but never have been damaged due to that. I will admit this is my first Mac, but I assume that Macs aren't anymore susceptible to this than any other computer.

 

I don't think it's good idea

read this:
http://support.apple.com/kb/HT3964

special this part:

"Resetting the System Management Controller (SMC)
...
Shut down the computer.
Unplug the computer's power cord.
Wait fifteen seconds.
Attach the computer's power cord.
Wait five seconds, then press the power button to turn on the computer.
"

it counts as a SMS reset, so probably not a good idea