Why your MacBook loses charge while it's asleep

How much should a sleeping MacBook lose?

Apple says a Mac in sleep is still turned on but uses much less power, and wakes faster than it starts up (Apple). Apple doesn't publish how much a sleeping MacBook should lose overnight, so the useful comparison is your own Mac on a good night.

For a reference point, here's what macOS's own log recorded on the M2 Max MacBook Pro we used for this guide (macOS 27.0.1), on battery:

• a 16-hour sleep that started and ended at 84%, with 73 brief wakes along the way;
• a 13-hour night that went from 63% to 54%, with 59 brief wakes. Four of those nine points went in the first hour.

Two nights on one Mac aren't a standard, but they show the range, and that the same Mac can behave differently from night to night. Three ways to measure yours:

• Note the percentage when you close the lid and when you open it.
• Open Activity Monitor › Energy in the morning. The graph at the bottom shows the battery level over the last 12 hours, so you can see whether it fell steadily, in steps, or not at all (Apple).
• Read the sleep log, which records the charge at every sleep and wake. Step 2 below shows how.

A Mac that's warm in your bag in the morning was probably awake for part of the night, whatever the percentage says.

Why a sleeping Mac still uses power

• Memory stays powered. By default a MacBook keeps its memory powered while asleep, so it can wake straight from memory, and also saves a copy to disk in case power runs out (man pmset, hibernatemode 3).
• Power Nap wakes the Mac periodically to update information. Apple says on battery it checks Mail, updates Calendar and other iCloud events; on power it can also download software updates and run Time Machine backups (Apple, macOS 26).
• Wake for network access lets other devices wake your Mac to use shared services.
• Brief wakes for maintenance. Over a week, the log on our Mac recorded 539 short wakes with the screen off, often several an hour. Three in four lasted 10 seconds or less; 18 ran longer than a minute.

Step 1: find what's keeping it awake

A Mac only goes to sleep on its own when nothing is asking it to stay awake. Start with Activity Monitor: open it from Applications › Utilities, click Energy, and look at the Preventing Sleep column. "Yes" means that app is stopping your Mac from sleeping.

For the full list, including system processes, run this in Terminal. It only reads, needs no administrator password, and changes nothing:

pmset -g assertions

Trimmed output from our Mac while it was in use:

Assertion status system-wide:
   PreventUserIdleDisplaySleep    0
   PreventSystemSleep             0
   PreventUserIdleSystemSleep     1
Listed by owning process:
   pid 602(sharingd): […] 00:02:29 PreventUserIdleSystemSleep named: "Handoff"
   pid 115(powerd): […] 00:58:59 PreventUserIdleSystemSleep named: "Powerd - Prevent sleep while display is on"

How to read it:

• A 1 next to PreventUserIdleSystemSleep means at least one process is stopping the Mac from going to sleep on its idle timer.
• Under Listed by owning process, each line names the process, how long it has held its request, and the reason it gave. Here, powerd's "while display is on" is expected, and sharingd's Handoff request is short-lived.
• Look for an app you don't expect, holding its request for hours. Quit it, or check its settings for an option like "prevent sleep while downloading".

For a one-line summary, pmset -g prints a line such as sleep 1 (sleep prevented by sharingd, powerd).

Apple lists other things that keep a Mac awake: people using shared services such as file or printer sharing, Spotlight indexing, apps reading from a disk, and malfunctioning USB or Thunderbolt devices (Apple).

Step 2: find what woke it

macOS keeps a log of every sleep and wake. The full log is long and noisy, so this filters it to the sleep and wake lines and shows the last 40. It's read-only and needs no password:

pmset -g log | grep -E '^[0-9-]+ [0-9:]+ [+-][0-9]{4} (Sleep|Wake|DarkWake)  ' | tail -40

The two spaces before the closing quote matter: they skip the much busier "Wake Requests" lines. Trimmed output from our Mac (time zone and some codes removed):

2026-10-13 18:56:06 Sleep     Entering Sleep state due to 'Maintenance Sleep' … Using Batt (Charge:80%)
2026-10-13 19:12:05 DarkWake  DarkWake from Deep Idle : due to … rtc/SleepService Using BATT (Charge:80%) 2 secs
2026-10-13 19:14:31 DarkWake  DarkWake from Deep Idle : due to … wifibt … Using BATT (Charge:80%) 9 secs
2026-10-13 19:15:29 Wake      Wake from Deep Idle : due to … lid … Using BATT (Charge:80%)

• Sleep is when it went to sleep. Wake is a full wake, with the display on. DarkWake is a short wake with the display off.
• "due to" names the trigger. On our Mac: rtc (a scheduled timer), wifibt (Wi-Fi or Bluetooth) and lid (opening the lid). Apple doesn't document these codes, so treat them as hints rather than a diagnosis.
• Charge shows the battery level at each event, which makes the overnight drop easy to measure.

What matters is the pattern. Dark wakes of a few seconds through the night are routine on our Mac. Dark wakes that last minutes, or full wakes you didn't cause, are worth chasing with the settings below.

Settings that make a difference

Wake for network access

Open System Settings › Battery, click Options, and use the pop-up next to Wake for network access. Apple suggests Never if you don't want other devices waking your Mac. If you rely on reaching your Mac remotely while it sleeps, leave it on. The path is the same on macOS 15, 26 and 27.

Power Nap

On macOS 15 and 26, the same Options panel has an Enable Power Nap pop-up menu where you choose when Power Nap runs. Apple's macOS 27 guide no longer lists Power Nap in this panel, although pmset -g on our macOS 27.0.1 Mac still shows a powernap setting. If you don't see the option, there's nothing to change.

Sharing

In System Settings › General › Sharing, turn off services you don't use. People using a shared printer or files on your Mac can stop it sleeping.

Accessories

Apple says a malfunctioning USB or Thunderbolt device can keep a Mac awake. Unplug everything for a night. If the drain stops, reconnect devices one at a time to find the one responsible.

Lid closed with an external display

If your MacBook keeps showing your desktop on an external display with the lid closed, it isn't asleep. It's awake and using power as normal, and nothing on this page applies until you unplug the display or put the Mac to sleep from the Apple menu.

Shut down or sleep?

Apple doesn't give everyday advice either way. What it does say: sleep uses much less power than being awake and wakes faster than a cold start, and for long-term storage you should charge the battery to about 50%, power the device off, and keep it somewhere cool, below 32 °C (90 °F), topping up to 50% every six months if it's stored longer than that (Apple).

In practice: sleep overnight and between uses. Shut down when you won't use the Mac for a week or more, or if your own nights show it losing more than you're comfortable with and you haven't found the cause yet.

How Tend helps

Tend's energy history doesn't count time asleep, so it can't show sleep drain itself. What it can show is which apps were busy right before you closed the lid: live per-app power, in estimated watts, is free, with 24 hours of history, or 30 days with Pro. Tend Pro can also send a notification when an app uses more than 4 W on battery, which needs notifications turned on (how Tend uses notifications).

Questions

Related guides

Sources

• Apple, Put your Mac to sleep or wake it
• Apple, Set sleep and wake settings for your Mac (macOS 15, 26 and 27 versions)
• Apple, Turn Power Nap on or off on Mac (macOS 26)
• Apple, If your Mac sleeps or wakes unexpectedly
• Apple, View energy consumption in Activity Monitor on Mac
• Apple, Batteries – Maximizing Performance
• man pmset and man caffeinate, and output from pmset on our MacBook Pro (M2 Max) with macOS 27.0.1, 6 to 13 October 2026

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