I am new to macOS. I recently purchased a 2019 iMac (Retina 4K, 21.5 inch).

               .OMMMMo           OS: macOS 10.15.1 19B88 x86_64 
               OMMM0,            Host: iMac19,2 
     .;loddo:' loolloddol;.      Kernel: 19.0.0 
   cKMMMMMMMMMMNWMMMMMMMMMM0:    Uptime: 18 mins 
 .KMMMMMMMMMMMMMMMMMMMMMMMWd.    Packages: 28 (brew) 
 XMMMMMMMMMMMMMMMMMMMMMMMX.      Shell: bash 3.2.57 
;MMMMMMMMMMMMMMMMMMMMMMMM:       Resolution: 2048x1152 
    kMMMMMMMMMMMMMMMMMMMMMMd     CPU: Intel i3-8100 (4) @ 3.60GHz 
     ;KMMMMMMMWXXWMMMMMMMk.      GPU: Radeon Pro 555X 
       .cooc,.    .,coo:.        Memory: 4009MiB / 8192MiB 

I have noticed that the Acivity Monitor reports the CPU utilization at around 75% -- even when I have all programs closed. About 65% reports as "System" usage, 10% "User", and 25% "Idle".

When I sort the processes by "% CPU" the kernal_task process is using the vast majority of the CPU (~250%).

activity monitor

Is this typical, or is it something to be concerned about?

Edit: added screenshot of Activity Monitor

Edit 2: added screenshot of Activity Monitor and output from ps -al command after booting into Safe Mode (see below)

enter image description here

  • I opened a case with Apple Support. After bouncing around between 4 different technicians, where I was asked to 1) shut down the machine, unplug from power, wait 30 seconds, plug it in, wait 5 seconds, then boot, 2) create a new admin user, 3) reset the NVRAM, and finally 4) reinstall from recovery mode. I am waiting for the reinstall to complete now... I have to say I'm not super impressed. Maybe I just have a dud? I will update the question with the results of the reinstall when it finally finishes. Commented Dec 9, 2019 at 2:38
  • Clicking on the kernel_task row in the table in Activity Monitor, then clicking on the "Gear" icon in the header above it, then choosing "Sample Process" from the button's context-menu will (hopefully) show you a report of what functions that task is spending most of your CPU cycles calling. That might (or might not) give you some indication about what it is trying to accomplish. Commented Dec 9, 2019 at 4:56
  • @JeremyFriesner You can't Sample or Inspect kernel_task, because it's not a 'real' process, but just 'everything the kernel is doing'.
    – benwiggy
    Commented Dec 9, 2019 at 7:30
  • Update: a day after the reinstall and I am still noticing the same behavior. I have tried disabling all Spotlight search locations, because some people mentioned that on a new install the Spotlight search indexes can take some time to initialize. However that has not seemed to impact the CPU utilization of kernel_task. Commented Dec 10, 2019 at 2:28

2 Answers 2


A new Mac may use a considerable amount of resources building the database for Spotlight. This may take several hours. but on a new machine, without a lot on it, maybe as low as 30 minutes. If you see a lot of resources being used I'd be concerned. My older iMac is currently just sitting here doing nothing but I have 7 web pages open. Activity monitor says the System is being used 6% of the time, user uses about 20% of the time and its ldle the remaining 74% of the time. Is this consistent with what you are seeing? These values are given on the CPU page to the right of the CPU Load plot.

Even when you are doing nothing, many processes are running in the background as you can tell by the amount of processes listed when you use activity monitor.

  • 1
    That is not consistent with what I'm seeing. I currently have one Firefox tab open and Activity Monitor; nothing else. The "System" CPU utilization remains ~65%. This has been continuing for a couple days (ever since I first turned on the machine out-of-the-box). I made sure to take the most recent OS update. I have attempted rebooting the machine, but the same behavior persists -- kernal_task is chewing up a reported ~250% CPU. Commented Dec 8, 2019 at 21:26
  • That is curious. Do you have many login items? You could reboot into safe mode and determine the use then. If something from login items is causing this it will show up when running in safe mode. You can boot into safe mode by holding down the shift key while you reboot. Once the apple logo appears on the screen you can release the shift key.
    – Natsfan
    Commented Dec 8, 2019 at 21:38
  • Thanks, I will try booting into safe mode and see if the issue persists. I am not sure how to answer the question about the number of login items... I set two users (my wife and I) if that is what you mean. Commented Dec 8, 2019 at 21:50
  • You have the process kernal task that seems at first glance to be the culprit. Are you running any processes you've forgotten about? Can you open a terminal window and type ps -al and see what processes of yours are running?
    – Natsfan
    Commented Dec 8, 2019 at 21:52
  • i meant login items the are usually apps that are set to run when you login. Your wife or you may have some.
    – Natsfan
    Commented Dec 8, 2019 at 21:54

Over time, you should be less than 1-2 % CPU with no processes needing to do work.

That process manages thermal and does other work. What does activity monitor look like, top 20 cpu users? https://support.apple.com/en-us/HT207359

What’s the ambient temperature of the air around the mac?

Also, check the memory, network and disk tabs of activity monitor. If you have IO happening (cloud download, network, spotlight indexing) then even with all apps you normally think of as being quit, the system can run for hours or days if there is work to be done in the background. The good thing, is these background tasks yield if you have front apps to run, so I would walk away for 6 hours and let things run, then check again.

In your case, sort by all CPU time and quit everything you can like Firefox and watch for 15 minutes to see if kernel is quieted. The energy tab also is great for seeing the last day and hour what’s stoking the kernel task fires.

  • I updated my question with a screenshot of Activity Monitor. The ambient temperature is 70 degrees F in my house. If I put my hand near the fan in the back of the iMac, the air coming out feels cool. The Memory tab shows ~4GB free memory (0 bytes swap used). The Disk and Network tabs show very little to no activity. Commented Dec 8, 2019 at 21:46
  • Excellent @JoeDegiovanni - without that detail I had to list the most abstract things. You’re not 90 degrees in the tropics, so this activity will be all in response to other programs assigning work to the core IO - network, file, thread, etc...
    – bmike
    Commented Dec 8, 2019 at 22:10

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