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Bugs Killed

Mac

My MacBook battery drains much faster since I updated macOS

A MacBook that used to last all day runs down in a few hours after a macOS update. Apple acknowledges a temporary hit to battery life right after an update, while the Mac finishes indexing in the background. Drain that is still there days later is not something Apple has acknowledged, so the next step is to find out which app or process is spending the energy.

Affects

Versions

  • macOS Tahoe 26

Apps

  • Safari
  • Electron based apps such as Slack, Discord, and VS Code

Hardware

  • MacBook Air
  • MacBook Pro

What you see

  • Battery percentage falls much faster than it did before the update
  • The Mac is warm and the fans run more often
  • Battery life is poor even when the Mac looks idle
  • The Mac feels slow for the first day or two after the update

Why it happens

Confirmed Apple states that "Immediately after completing an update, particularly a major release, you might notice a temporary impact on battery life and thermal performance". It is normal, because the Mac needs time to "complete the setup process in the background, including indexing data and files for search", download new assets and update apps. [1]

Confirmed Apple also notes that some new features may require additional resources, so depending on usage some people notice a small ongoing impact on performance or battery life. [1]

Suspected Drain that outlasts that first period has no vendor acknowledgement behind it. On macOS Tahoe, OS X Daily reports battery drain that continues after the indexing is done, and points at long-open Safari tabs and an Electron app issue as things to look at, so the cause of a long tail is unconfirmed. [2]

When it shows up

The macOS update finished in the last day or two

You are in this case if:

  • The update was installed within the last day or few
  • Activity Monitor shows background processes busy while you are not doing anything
  • The Mac is warm and battery life is poor even at low brightness

2 fixes below

It is days later, the indexing is long finished, and the battery is still poor

You are in this case if:

  • More than a few days have passed since the update
  • Activity Monitor shows a normal app, not a system indexing process, at the top of "Energy Impact"
  • Battery life is still far below what the same Mac used to do

3 fixes below

The steps that killed it

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Keeping it away

  • Plan a macOS update for a time when the Mac can sit on power for a day, so the indexing happens while it is plugged in.
  • Keep apps updated as well as macOS, since a heavy app on an old build can be what is spending the battery.

Sources

  1. About Apple software updates
    Apple Support, 2026-07-10
  2. macOS Tahoe Battery Life Worse? Tips for Battery Issues with MacOS 26
    OS X Daily, 2025-10-14
  3. How to update macOS on your Mac
    Apple Support, 2026-06-01
  4. What's new in the updates for macOS Tahoe 26
    Apple Support, 2026-08-17

Last verified 2026-09-14