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High CPU and battery drain in Sierra for Calend...

Since upgrading to Sierra (from Yosemite) I've been plagued with high CPU usage by these two processes.  They seem to be on a schedule, so my battery life is only a few hours and overall CPU utilization in Activity Monitor looks like this:

I've tried everything I could find to alleviate this problem.  I've turned off calendar syncing from every account (I have both iCloud and Google).  I turned off notifications and removed all widgets for everything.  I deleted the calendar cache, and even the entire calendars directory (~/Library/Calendars).  I've looked in the console app for bad logs related to these processes and find no errors (but lots of normal looking activity).

Reboots do not help.

If I remove calendar sync for all accounts, boot to safe mode, reboot to regular mode again, then the CPU drops for a while.  Even if I add back an account for syncing, it does the initial sync and then CPU drops and is stead with low utilization.  But then after a while (a few hours) I notice the high CPU again.

At this point I have only iCloud calendars syncing, not Google.  So I know that's not the root cause.

One final note, I did "upgrade" my iCloud notes when prompted to the newer notes after upgrading to Sierra.  It feels like that was the point I noticed the problem, but I can't be sure it wasn't already happening as that was pretty soon after the Sierra upgrade.

Is anyone else seeing this?

Any help is appreciated.

Ok, I have as close to a permanent solution as possible.  The issue seems to be caused by some trigger I have not yet identified, but it might have something to do with a combination of connecting/disconnecting an external monitor and going into sleep mode.  The less often I do those things, the fewer times this issue returns.

To resolve the problem when it happens, I have to de-select "contacts" from both of my google accounts.  Then wait for the CPU to settle down to near-zero.  Then I can re-select both accounts.  That jumps the CPU for a few minutes while it synchronizes, but after that it's steady and low until the next time the issue returns.

At this point I'm performing this process less than once per week, so it's tolerable.  Still, it would be nice if Apple would figure this out and get it resolved.  But with the few number of views and replies on this thread, I suspect it's totally unknown to them.

Exactly same issue here.

I'm having one iCloud and an Exchange account.

Update:

I have disabled syncing from everything but mail from my 2 accounts (one Gmail, one Yahoo), and Find-My-Mac, and then rebooted to safe mode and then back to normal mode, and now CPU is steady and low.  I did not clear out the cache for calendar, contacts, or anything else (which means it didn't need to do a full sync when I re-enabled).

Then, one by one, I added back each account that needs to sync.  The list is as follows:

• iCloud - Reminders
• iCloud - Safari (which raised CPU for a while, but then it dropped again)
• iCloud - Notes
• iCloud - Calendar
• Gmail Account 1 - Contacts
• Gmail Account 2 - Contacts

After doing all of this and monitoring CPU at each step, I have now finished out the day (5-6 hours) with steady and low CPU usage.

I think I had this result once before... and the next day the CPU was high again.  I'm wondering if it has anything to do with my MBP going to sleep and then waking up.  I'm on it all day, so it never sleeps, but in the evenings I walk away and off to bed it goes.  We will see tomorrow what happens, but maybe if standby mode has something to do with it I could automate a reset script to do all this when it wakes up, or maybe even get Apple to identify and fix the issue.  I'll know more tomorrow.

I have the same thing happening on my iMac (27-inch, Late 2012)

Sierra: 10.12.2

I read a post mentioning issues with the stock Reminders app, so I removed all reminders and other lists. This took CalendarAgent and CalNCService from 50% and 40% to 20% and 15% respectively.

I found a solution that worked for me!

Via: https://robert.accettura.com/blog/2012/08/19/how-to-stop-calendaragent-from-eati ng-cpu/

CalendarAgent is essentially Calendar’s backend (that’s how it’s also able to power the notification center). The best resolution I’ve found is to completely clear out the calendar and recreate it. Process I used was as follows:

1. Remove the Calendar from “Mail, Contacts & Calendars” pref panel (just uncheck from the account). Then go into Calendar and make sure the account is removed. If it’s not, remove it.
2. Delete ~/Library/Calendars/
3. Delete ~/Library/Preferences/com.apple.iCal.plist
4. Go back into the “Mail, Contacts & Calendars” pref panel, put the calendar back. Give it some time to download.

Correction: while this solution did work, once I opened reminders or calendar app, it came right back.

I'm out of ideas.

Ok, I have as close to a permanent solution as possible.  The issue seems to be caused by some trigger I have not yet identified, but it might have something to do with a combination of connecting/disconnecting an external monitor and going into sleep mode.  The less often I do those things, the fewer times this issue returns.

To resolve the problem when it happens, I have to de-select "contacts" from both of my google accounts.  Then wait for the CPU to settle down to near-zero.  Then I can re-select both accounts.  That jumps the CPU for a few minutes while it synchronizes, but after that it's steady and low until the next time the issue returns.

At this point I'm performing this process less than once per week, so it's tolerable.  Still, it would be nice if Apple would figure this out and get it resolved.  But with the few number of views and replies on this thread, I suspect it's totally unknown to them.

I have tried all solutions listed here(clearing cache, removing/adding accounts, removing/adding one account service component at a time) and other threads but no matter what I do, CalNCService keeps returning to >100% usage.

This problem happens continuously back to 2012.

How is that possible that it is STILL not fixed? Even after thousands of user's reports?

I was tired of "svchost.exe" eating 100% CPU on Windows, switched to macOS and now story goes again. Where is famous Apple quality?

Developer of CalNCService should be fired immediately.

Same here - really disappointing!

Thank you so much.  I had this problem and tried your temporary fix of unchecking the contacts in my google account and it worked.  I don't know why, but this makes a huge difference to my CPU loading. 

Best wishes,

I'm using a MBP mid-2015 with MacOs Sierra 10.12.5. I was scratching my head trying to find solutions and finally found it.