High Cpu System Usage

What is the exact model of your laptop? You can get this information by clicking the Apple menu and selecting "About this Mac".

Try an SMC reset.

If you have a MBPro with Touchbar, then try plugging the charger into the right side USB-C ports instead of the left side. I know this sounds crazy, but I've seen a report that this is a bug.

Run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper.

It also doesn't hurt to run the Apple Diagnostics.

Hello Honey_alison,

Thank you for contacting Apple Support Community! I see you are having issue with tasks taking most of your CPU usage percentage.

Check out these articles that have information related to your issue and can help you trouble shoot the issue further.

How to use Activity Monitor on your Mac.

See how apps affect Mac performance, battery runtime, temperature, and fan activity.

If kernel_task is using a large percentage of your Mac CPU.

Take Care!

I don't see anything in the report. Did connecting the charger to the right side ports make any difference?

If not, then run Disk Utility First Aid. Make sure to examine the details of the First Aid report to see if any errors are listed. If there are any errors even if Disk Utility says everything is Ok, then I would make sure you have a backup of the system, then perform a clean install of macOS by first erasing the physical drive using these instructions:

https://support.apple.com/en-us/HT208496

It is important to test the laptop before restoring or migrating from the backup or before installing any third party apps so you don't contaminate the clean install. If you still have a problem, then it means you have a hardware issue or have found some odd macOS bug with the latest update. Erasing the physical drive is critical so that is creates a new APFS file system free of any errors. I just had one of our organization's laptops have an issue where the file system errors caused severe issues even though Disk Utility First Aid said everything was "OK", but the details of the scan showed multiple errors.

If a clean install works, then you have to decide how to restore your data and account(s). You can try the whole system restore (erasing the drive again and restore from backup) or migration (migrate user account, possibly settings & apps), but there is always a chance it could include a problem which will be transferred back. If you try the full system restore or full migration, then be prepared to do this a couple of times if you transfer the problem back so you may need to migrate just you user account(s) and data only.