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I want to keep my iMac on tonight and seed/leech torrents. I usually leave it there until, after 5/10 min or so, the iMac turn the monitor off. I can still hear the hd working.

uTorrent has an option which "prevent sleep when transfers are active" so I guess if the iMac goes in sleep mode I can't seed/leech torrents.

Told so, how can I reduce power consumption? And how can I measure the power I'm using now to decide if it is ok or I shouldn't leave it on?


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up vote 2 down vote accepted

There's not that much you can do apart from turning the display off. Either wait for it to turn off automatically or press ⌃⇧⏏.

You could also open Activity Monitor and check if any processes are using CPU, but most of them are usually close to idle.

New iMacs use about 15-20W of power when they are idle and the display is turned off. The average energy consumption might be closer to 20-25W, but that's still just about 0.002-0.004 USD or EUR per hour.

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Yes, if the mac sleeps, you can't run any processing. Apple have released as part of Mountain Lion a background system that can run while asleep (PowerNap), but that's not open to other apps, and also needs a laptop with a flash drive. Besides, torrents require a fair amount of processing of the data, lots of network traffic and HD activity.

Your best bet is to use the Energy Saver panel in System Preferences to get the screen and computer to sleep after short period of time. You can also check the HD option.

Not sure about uTorrent but Transmission lets you prevent computer sleep when there are active transfers, and you can set limits on when to stop the transfer. So, you can have it set to seed a certain amount after it's finished downloading, then remove it automatically, and your computer will then sleep.

As for measuring power, something like this is what you need:

Plug the iMac into it and it'll tell you the actual power used. There are a bunch of similar devices, but the Kill-A-Watt ones are pretty well known and widely used.

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For iMac user without Apple's keyboard for any reason. Use this command to just turn off the display.

pmset displaysleepnow

You can alias it to a shorter version in your favorite shell profile like ~/.bash_profile

alias displayoff="pmset displaysleepnow"
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