What's draining your Mac's battery?

Your Mac's battery is dropping faster than it should, and nothing on screen tells you why. The good news: macOS already knows what's draining your Mac battery. It just spreads the answer across a few built-in tools that don't advertise themselves. No "battery saver" app required. Here's how to read them, from a two-second glance to the command line.

The two-second check for what's draining your Mac battery: the battery menu

Click the battery icon in the menu bar. If an app is burning through power, macOS lists it under Using Significant Energy. Apple decides what lands there based on an app's "CPU usage, disk I/O, networking, and numerous other factors," so it catches more than just a busy CPU. If something you're not actively using shows up, quit it.

While you're there: a Display Brightness icon appears when your screen is cranked high. Clicking it drops brightness to about 75%, which is often the single biggest easy win on battery.

Activity Monitor → Energy: which app, and how much

For the real breakdown, open Activity Monitor (in Applications → Utilities, or search it in Spotlight) and click the Energy tab. Sort by Energy Impact. Apple defines it as "the current energy consumption of the app (lower is better)."

A few columns are worth knowing:

• Energy Impact: the right-now cost. Good for catching what's hot this second.
• 12 hr Power (laptops only): the average impact over the last 12 hours, or since the Mac started up. This is the one that catches the quiet drainers: an app that looks calm right now but has been costing you power all afternoon.
• Preventing Sleep: whether the app is holding the Mac awake. A "yes" here on something trivial is a classic overnight-drain culprit.
• Graphics Card: on Macs with two GPUs, flags apps that "require a high performance graphics card," i.e. ones waking the power-hungry discrete GPU.

One caveat up front: Energy Impact is a relative number, not watts. It's Apple's blended indicator of how demanding an app is, useful for ranking who's worst, not for saying "Chrome used 4.2 watts." Anyone quoting exact wattage off this screen is guessing. Read the figures as impact, not a meter.

System Settings → Battery: the last 24 hours and 10 days

To see the trend instead of the moment, open System Settings → Battery (macOS Ventura and later). You get two views, Last 24 Hours and Last 10 Days, showing your battery level over time (with charging periods shaded), energy usage per day, and screen-on time. A cliff in the graph at 2 a.m. tells you the drain happened while you weren't using the Mac at all, which points at sleep, not apps.

What's blocking sleep: pmset (optional, command line)

If the drain happens with the lid closed, the culprit usually isn't an app you can see; it's something keeping the Mac awake. Two read-only commands (no sudo needed) tell you what:

pmset -g assertions

This lists the power assertions currently in effect. An assertion is an app telling macOS "don't sleep, I'm busy." If a media app or a background agent is holding one, you'll see it named here.

pmset -g log | grep -E "Sleep|Wake"

This shows the history of sleeps and wakes. DarkWake entries are the Mac briefly waking on its own (to fetch mail, sync, or run Power Nap) without lighting up the screen. A machine that dark-wakes every few minutes all night will be noticeably down by morning.

The usual suspects (and what to do)

These are the widely reported repeat offenders. None of them are bugs. They're normal features that happen to cost power:

• Browser tabs, especially Chrome. Chrome runs each tab as its own process, and its engine is generally less power-efficient than Safari's WebKit, so it's consistently near the top of macOS drain lists. Fix: close tabs you're not using, and reach for Safari on long unplugged sessions.
• Spotlight indexing (mds / mds_stores). After a big file move, a migration, or a new drive, macOS re-indexes everything, heavy on CPU and disk until it finishes. Fix: usually just wait; it's temporary. If it never settles, that's worth chasing on its own.
• Background cloud sync: Dropbox, Google Drive, iCloud, Photos analysis, backups. They wake the disk and network behind the scenes. Fix: pause sync when you need the battery, and let big first-time syncs finish while plugged in.
• Apps preventing sleep. Anything with a "yes" in the Preventing Sleep column (or an assertion in pmset) is a candidate. Fix: quit it, or check its settings for a "keep awake" option.
• The discrete GPU waking up. On dual-GPU Macs, one app asking for the high-performance graphics card keeps it powered for everything. Fix: find it in the Graphics Card column and quit it when you're on battery.

Two related things people mistake for battery problems: if kernel_task is pinning your CPU, that's a thermal response, not a drain in itself. See kernel_task using high CPU. And if your memory pressure sits in the red, the constant swapping to disk burns power too, which is covered in memory pressure explained.

The honest bottom line

Everything above is built into macOS. You don't need a battery-saver app to find a drain. You need to know which three screens already hold the answer, and to remember that the numbers are impact indicators, not exact watts. Read them, quit the worst offender, and check whether anything is holding the machine awake at night.

You can chase all of this across the battery menu, Activity Monitor, and pmset. It works, but you're reading four tools and doing the "is this impact number actually bad?" math in your head. Plumby puts it in your menu bar instead: it shows where your power went over the last hour and the last 12, in real units labeled as estimates with the method shown, and lets you watch it run live next to a plain list of what's currently preventing sleep. Nothing is fabricated, and it only reports. It never quits or changes anything on its own.