On the 15-inch MacBook Air M4 the battery complaint that stands out is not the one while you work but the one while the lid is closed. Apple Community threads describe an M4 Air that drops from 100 percent to 90 or 95 percent overnight, and some owners report as much as 30 percent, with the problem worse after the macOS 26.3 update.
Reports of logs with repeated wake and sleep-prevention assertions suggest something is keeping the Mac awake: a USB hub or an external SSD that stays powered, Safari tabs, or a background process. The 15-inch has the larger battery of the two Airs, so a drain that you notice is a signal, not a size problem. Work through it in the order Apple gives: what the Battery page says used the power, battery health, then what is plugged in when the lid is shut.
Differential
Likely causes of “Apple MacBook Air 15-inch (M4) battery drains too quickly”, and how to tell them apart
- 1
A hub, dock or external SSD that keeps the Mac awake
What separates it The Air loses 10 percent or more overnight with the lid closed and something plugged in
How to confirm Unplug every USB hub, drive and display before closing the lid and compare the next morning
- 2
A wake assertion from a background process
What separates it pmset logs show repeated wake and sleep-prevention activity
How to confirm Terminal: pmset -g assertions shows what is keeping the Mac awake; quit or update that app
- 3
Safari tabs and web apps left open
What separates it Memory use is high and the Mac does not settle in sleep
How to confirm Close heavy tabs and quit browsers before closing the lid
- 4
macOS Tahoe indexing after an update
What separates it Drain and warmth in the first days after an update
How to confirm Plug in and leave the Mac idle so indexing finishes, then compare
- 5
An aged battery
What separates it Maximum capacity is low, or the status reads Service Recommended
How to confirm System Settings, Battery, Battery Health
Before you touch a setting
Record this first — changing settings destroys the evidence
- The percentage lost overnight with the lid closed and nothing connected
- Whether a hub, drive or display is plugged in when you close the lid
- The output of pmset -g assertions at the moment the Mac should be asleep
- The macOS version, since reports tie the worst drain to 26.3 and later
Try in this order
0 of 6 completedRun a clean overnight test
ReversibleQuit apps, unplug everything, close the lid and note the percentage at bedtime and in the morning.
Look at what is keeping the Mac awake
ReversibleIn Terminal run pmset -g assertions with the lid open and note any process that prevents sleep.
Check the Battery page
ReversibleSystem Settings, Battery: the last 24 hours and 10 days show which apps used power.
Unplug before you close the lid
ReversibleA powered hub or an SSD can keep ports awake and drain a closed Mac.
Let Tahoe settle after an update
ReversibleLeave the Mac plugged in and idle for a day after a major update.
Check battery health
ReversibleSystem Settings, Battery, Battery Health: Maximum Capacity and the status message.
Model-specific
What is true of this model and not of its siblings
- The 15-inch M4 Air
- A 15.3-inch Liquid Retina display, the M4 chip, six speakers, two Thunderbolt 4 ports and MagSafe 3, with a larger battery than the 13-inch.
- Reported pattern
- Overnight loss in Apple Community threads ranges from 5 to 30 percent after macOS 26.3.
Stop boundary
When this stops being a self-service repair
- !If a clean overnight test with nothing connected still loses ten percent or more, ask Apple to run diagnostics and include the pmset output
- !If Battery Health says Service Recommended, book the battery replacement; AppleCare covers it at below 80 percent
- !A swollen battery is a same-day visit
Evidence ledger
Sources behind this answer
Maximum capacity and service messages.
Charging On Hold and Charge Limit.
Cycle count lookup.
M4 Air owners describing overnight loss in sleep.
Owners tying sleep drain to macOS 26.3.
Six speakers, Thunderbolt 4, two external displays and ports for the 15-inch M4 Air.
Exact questions
Common questions
Why does my MacBook Air M4 lose battery in sleep?+
Owners report 5 to 30 percent overnight on macOS 26.3 and later. A connected hub or drive, a wake assertion or open Safari tabs are the usual causes.
How do I see what keeps my Mac awake?+
Run pmset -g assertions in Terminal; it lists the processes that prevent sleep.
Is 10 percent overnight normal on an Air?+
No, it should lose only a few percent; a clean test with nothing connected tells you whether it is software.
Does Optimized Battery Charging hold the Air at 80 percent?+
Yes, on purpose, and the battery page says so.