If your MacBook started running hot, spinning its fans, or losing charge far faster than usual right after you updated to macOS Tahoe, you're not imagining it — and you're not alone. Since macOS Tahoe (macOS 26) rolled out, owners across forums and support communities have reported the same thing: a Mac that felt fine on the morning of the update, then suddenly warm to the touch and flat by lunchtime.

The good news is that, for most people, the cause is software — and the fixes below cost nothing. The important part is knowing how to tell ordinary post-update drain apart from a battery that's genuinely failing, because the symptoms can look identical. Here's how to work through it calmly.

Why your MacBook battery got worse straight after the update

A major macOS upgrade changes how your Mac draws power, and it usually takes a few days to settle. Two things in particular are being widely reported with Tahoe.

The "Liquid Glass" interface and your graphics chip

Tahoe introduced a redesigned, translucent interface that several technical publications report places more load on the graphics processor than the flatter look in earlier versions of macOS. More GPU work means more heat and more power use, especially on older MacBooks. The exact figures quoted online vary by source and aren't confirmed by Apple, so treat specific percentages as estimates rather than fact.

Electron apps (Slack, Discord, VS Code) and background tasks

Apps built on the Electron framework — common examples include Slack, Discord and Visual Studio Code — each run their own browser engine in the background. On Tahoe, these have been repeatedly singled out as heavy battery users while the software ecosystem catches up. On top of that, every major update spends the first day or two re-indexing your files for search and re-optimising itself, which temporarily spikes heat and battery use.

Alt text: macOS settings screen showing the Reduce Transparency option switched on.

Free fixes to try first (no parts, no cost)

Work through these in order. Give your Mac a day of normal use between steps so you can see what actually helped.

Turn on Reduce Transparency

This is the single most effective software tweak reported for Tahoe battery life. Go to System Settings → Accessibility → Display and switch on Reduce Transparency. It tones down the translucent effects and noticeably lightens the load on your graphics chip.

Find and quit the apps draining your battery

Click the battery icon in the menu bar to see which apps are "Using Significant Energy". Open Activity Monitor (in Applications → Utilities) and check the Energy and CPU tabs. If a messaging or chat app is sitting near the top while you're not even using it, quit it and see if things improve. Where you can, using the built-in Apple apps — Mail, Safari, Notes — instead of a heavier third-party equivalent will save power.

Let indexing finish, then restart

If the update was recent, leave the Mac plugged in and awake for an hour or two so background indexing can complete, then restart. A lot of "the update killed my battery" reports quietly resolve themselves once this finishes.

Check for the latest macOS Tahoe update

Apple released macOS Tahoe 26.5.1 in June 2026 with thermal-management and efficiency improvements. Go to System Settings → General → Software Update and install anything pending — point updates frequently address exactly this kind of post-launch power regression.

Alt text: A MacBook with a slightly raised trackpad, a warning sign of a swelling battery, on a repair mat.

When it's NOT just software — the warning signs

If you've tried the steps above and your Mac is still running hot or flattening quickly, or if you notice any of the following, stop and get it looked at. These point to hardware, not settings.

Battery swelling and an uneven trackpad

Sudden shutdowns and "Service Recommended"

If your Mac switches off without warning, even with charge remaining, won't hold a charge, or shows "Service Recommended" or "Service Battery" in its battery settings, the cell or charging circuitry likely needs attention.

How to check your MacBook battery health

You can see your battery's condition in seconds. Open System Settings → Battery → Battery Health and click the ⓘ. You'll see a status of either Normal or Service Recommended, and on many models, a maximum-capacity percentage. As a rough guide, a healthy battery holds around 80% or more of its original capacity; well below that, after a few hundred charge cycles, you'll feel it in everyday runtime. If the status says Service Recommended, the free software fixes won't bring the runtime back — the battery itself is worn.

Alt text: The Macrotech Solutions repair workbench in Carrum Downs with professional tools and a MacBook open for battery service.

Getting it checked locally in Carrum Downs

If you're in Carrum Downs, Frankston, Cranbourne, Langwarrin, Seaford, Skye, Patterson Lakes or anywhere along the southeast Melbourne corridor, you're welcome to bring your MacBook in for a battery health check. At Macrotech Solutions, we run component-level diagnostics. So rather than guessing, we measure whether you're looking at a software setting, a worn battery, or a charging-circuit fault on the logic board, and give you a clear written quote before any work begins. If it turns out to be a simple settings fix, we'll tell you that too.

Genuine battery replacements are carried out in-house and carry a 12-month warranty on parts and labour. If you suspect swelling, it's safest to power the Mac down and bring it in sooner rather than later.

Frequently asked questions

Macrotech Solutions is an independent repair centre and is not affiliated with Apple Inc. "Mac", "MacBook" and "macOS" are trademarks of Apple Inc., used here for description only.