MacBook battery draining fast? Here's how to find what's using the power

First, see where the power is going

Guessing wastes an afternoon. Your Mac already tracks this, in two places worth reading before you change anything. Open Activity Monitor (⌘ Space, type Activity Monitor) and click the Energy tab. The Energy Impact column ranks what is spending your battery right now, and the top row or two is usually the whole story.

From Terminal, the battery's own state:

% pmset -g batt

Now drawing from 'AC Power'
 -InternalBattery-0 (id=########)	80%; AC attached; not charging present: true

Shows the power source and the charge. This Mac was plugged in when the reading was taken; unplugged, the same line reports the charge and says it is discharging.

Something is holding your Mac awake

The charge drops overnight or in your bag. You closed the lid at 80% and opened it at 40%, having used it for nothing.

A Mac with the lid shut should be asleep and spending almost nothing. Apps can prevent that. macOS lets a program say “do not sleep while I am working” — a request called a power assertion. A backup, a download, a media app or a video call all make one legitimately, and a stuck app can hold one for hours after it should have let go.

One command lists every one of them, and names the app responsible:

% pmset -g assertions

Assertion status system-wide:
   PreventUserIdleSystemSleep     1
   InternalPreventDisplaySleep    1
Listed by owning process:
   pid 530(powerd): [0x0017e2cd00019d04] 00:07:03 PreventUserIdleSystemSleep named: "Powerd - Prevent sleep while display is on"
   pid 613(cupsd): [0x0000005e00118001] 445:19:31 NetworkClientActive named: "org.cups.cupsd"
   pid 85358(caffeinate): [0x0017e46b00019d43] 00:00:09 PreventUserIdleSystemSleep named: "caffeinate command-line tool"

The top block is what is in effect now. In the list below it, the name in brackets is the app, and the time is how long it has held on. Read the rows beginning PreventUserIdleSystemSleep, PreventUserIdleDisplaySleep or NoIdleSleep — those are the ones keeping the Mac awake. A row like NetworkClientActive does not stop it sleeping. An ordinary app you installed appears in exactly this format.

An app near the top of that list holding a sleep assertion for hours is your answer. Quit it and run the command again to confirm the row is gone.

Fixquit the app named in the row, saving your work first. If it comes back after every restart, look for a setting in it for background activity, and update the app. Holding sleep off for hours after you stopped using it is a bug. A Mac that wakes rather than stays awake is a different problem, covered in the self-waking guide.

One app is working the processor hard

The drain happens while you use the Mac. It runs warm, and the charge falls steadily even during light work like email.

Work costs power. When one program pins the CPU — the chip that does your Mac's work — the battery pays for it continuously. The usual causes are a browser holding heavy tabs such as video or web apps, a sync that has stuck and is retrying forever, or a creative app rendering in the background.

The Energy tab names it. From Terminal, the live view:

% top -o cpu

Ranks by processor use, highest first. Press q to quit. The top row or two is what is spending the battery.

Fixquit the app at the top, saving your work first, and watch whether the drain settles over the next few minutes. For a browser, open its own task manager (in Chrome: Menu > More Tools > Task Manager) to find the exact tab or extension, and close only that.

NoahNoah reads the running processes and names the ones working the processor hardest, with a percentage for each. With your approval it can quit the one you point it at — save your work in it first. It has no battery reading of its own: no cycle count, no health, and no list of what is holding the Mac awake. Those three are the checks above, and they are yours to make.

Temporary background work, usually after an update

Heavy drain for a few hours, starting right after a macOS update or a large photo import.

macOS runs catch-up jobs after a big change. Indexing — the work that catalogs your files so search is instant — runs after an update, and Photos analyses a newly imported library. Both are real work, both spend real battery, and both stop on their own.

Fixleave the Mac plugged in and give it a day before treating this as a fault. If it runs hot the whole time, the overheating guide covers what to check.

The battery itself may be worn

Nothing is holding it awake, nothing is pinning the chip, and it still runs out far sooner than it did two years ago.

Batteries wear by use, and Apple measures that in charge cycles. A cycle is not one charge. Apple's definition: one happens “when you use all of the battery's power—but that doesn't necessarily mean in a single charge.” Half a charge today and half tomorrow is one cycle. Apple designs a battery “to retain up to 80% of its original charge capacity at its maximum cycle count,” so shorter runtime after a few years is expected rather than broken.

Read yours in System Settings > Battery, next to Battery Health. Apple also documents the full detail under System Information: hold Option, click the menu, choose System Information, then select Power. From Terminal:

% system_profiler SPPowerDataType | grep -A4 "Health Information"

      Health Information:
          Cycle Count: 109
          Condition: Normal
          Maximum Capacity: 94%

Cycle Count is how many full cycles the battery has been through. Condition is Apple's verdict. Maximum Capacity is what it holds now against when it was new — 94% here, after 109 cycles.

Condition: Normal means the battery is behaving. Service Recommended means, in Apple's words, that “your battery's ability to hold charge is less than when it was new, or it isn't functioning normally.” That is not an emergency. Apple's guidance is that “you can safely continue to use your Mac, and if the lowered charging capacity is affecting your experience, you can get service.”

Fixif Condition reads Service Recommended and the Mac no longer lasts away from the wall, book a battery replacement. If it reads Normal, the battery is not your problem and the cause is one of the sections above.

Brightness, accessories, and Low Power Mode

These will not rescue a Mac with a stuck app holding it awake, but they are free and they add up. Apple's own energy guidance:

• Dim the screen. Apple's advice is to “dim the display to the lowest comfortable level” — the screen is one of the largest single draws on a laptop.
• Unplug what you are not using. Apple names accessories directly: “disconnect any accessories that you aren't using, such as external hard drives.” A bus-powered drive or a hub runs off your battery.
• Quit apps rather than leaving them open. In Apple's words, “even an app you aren't using may be working in the background and consuming energy.”
• Turn on Low Power Mode. It “reduces energy use to increase battery life.” Find it in System Settings > Battery, and set it to run on battery only.

The short version

1. Charge falling with the lid shut? Run pmset -g assertions and quit whatever holds a sleep assertion.
2. Charge falling while you work? Activity Monitor > Energy, and quit the top app.
3. Updated or imported recently? Give it a day plugged in — it finishes on its own.
4. Still fast? Read Battery Health. Service Recommended means a worn cell; Normal clears it.
5. Then the free ones: dim the screen, unplug idle accessories, turn on Low Power Mode.