I have a MacBook Pro (Retina, 13-inch, Early 2015) MacOS High Sierra 10.13.2

Sometimes my mac using a lot of CPU power. The usage is 75% of the system. But this occurred when I was away and the mac was in the sleep mode (I went away at about 11 AM till 8 PM). Also, the "User" usage is used more power than even when it is on. Does my Mac has some problems or is this behavior normal? Can it be a Virus? enter image description here

I checked the last 30 days. It happened more than ones. They are lasting for about 3 days... enter image description here

  • what did you use to get this table and plot?
    – Natsfan
    Jan 15, 2018 at 22:19
  • @jmh istat menus Jan 16, 2018 at 11:25

2 Answers 2


I'm wondering if this is the "Power Nap" feature of macOS...

Check System Preferences > Energy Saver

Is Power Nap checked? That feature will let the Mac do some things in the background while sleeping. Things that use little actual battery power. That is shows 100% CPU usage is odd, so I am not certain this is Power Nap.

  • Yes, Power Nap is on. I guess the only way I can understand is to be at that time at the Activity Monitor Jan 16, 2018 at 7:21

I'm looking at the graph, and "Power nap" is involved, but not the issue itself. Wakes are clearly visible from 03:00-06:00, but something heavy started around 10:35 and prevented the mac from entering sleep mode. Subsequent wakes are visible. It could be time machine backup (unlikely) or crashed/playing on background browser or other process.

From this screenshot it's unclear, but when this happens, you could use Activity Monitor -> Energy to see what consumes most energy and does it prevent sleep.

  • I have added a 30 days graph. This problem lasts sometimes for 3 days!... I will look forward to using activity Monitor when it happens. But is there nothing I can check now? Jan 16, 2018 at 7:27

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