i just updated to el captain and my iMac wakes up on its own throughout the day. I unplugged the USB printer and fixed the energy saver on stems preferences.
iMac, OS X El Capitan (10.11.1)
Check to see if Wake for Network Access is checked in the Energy Saver preference.
It is unchecked. I even tried to set it to sleep and it still wakes up.
If you can, time whoever the computer turns on; that way, you'll be able to determine if the interval is regular or irregular.
If it happens at a predictable interval, then it's probably fixable through System Preferences; if it happens at unpredictable intervals (like after ten minutes, then something like forty minutes), it's probably another issue.
The most common fix is to go to System Preferences/Energy Saver, and say what your settings are. An Entrecheck scan should say what applications are accessing your wake/sleep options.
Reset the PRAM, if that does not help please post an EtreCheck report of the system and post the results in your reply here. We can then look for any obvious issues. If you don't know how to reset the PRAM please click Intel iMac SMC and PRAM resets
My iMac wakes up on its own
