Idle Wake Ups

Click the CPU tab, then choose View > Columns and make sure Idle Wake Ups is checked. Click the column header to sort by it.

Common causes are apps that poll for updates on a short timer, animations running in windows you cannot see, and sync or chat apps that keep connections active. Browsers with many open tabs can also produce a lot of wakeups.

macOS reduces this for hidden apps with features such as App Nap, which slows the timers of apps you are not using.

When every core is idle, the chip can power down shared parts of the processor, not only the cores. Apple's powermetrics manual explains that a timer or interrupt that ends this deep idle state costs more energy than the same work done while the CPU was already awake.

So an app can use almost no CPU time and still keep the Mac from resting. Each wakeup is short, which is why it barely shows in % CPU, but the chip never gets to stay in its lowest power state for long.

macOS reduces this by grouping timers that are due at about the same time, so the CPU wakes once for several of them. Apple calls this timer coalescing. App Nap goes further for hidden apps by firing their timers less often.

1. Quit or hide the apps you are actively using, so the list shows background behavior.
2. In Activity Monitor, click the CPU tab and sort by Idle Wake Ups.
3. Watch for a minute. Note apps that stay near the top while you are not using them.
4. Click the Energy tab and check whether the same apps also rank high on Energy Impact.
5. For a Terminal view, run top -o idlew -stats pid,command,cpu,idlew. The IDLEW column is a running total, so watch which values climb fastest. Press q to exit.
6. For a more detailed sample, run sudo powermetrics --samplers tasks --order wakeups -n 1. It lists timer and interrupt wakeups per process, sorted by the wakeups that pull the chip out of idle.

There is no number that is always too high, since the count depends on the app and on how long it has been running. What matters is the pattern.

• Normal: system processes such as kernel_task and WindowServer near the top. They handle hardware events and drawing, so they wake the CPU often by design.
• Normal: apps playing audio, in a call, or keeping a live connection open while you use them.
• Worth a look: a hidden app you are not using that keeps climbing fast, especially if it also shows No in the App Nap column.
• Worth a look: small menu bar utilities that refresh often, such as clocks with seconds or live stats. Many let you pick a slower refresh interval in their settings.

Check the app's settings for a refresh or sync interval and make it longer. Turn off live previews or animations you do not need. Update the app, and if the problem stays, tell the developer: Apple asks developers to keep timers to a minimum, so a constant stream of wakeups from an idle app is a bug worth reporting.