Power usage on a Mac: what the energy figures mean

27 October 2026 · 5 min read

A power or energy figure next to an app on a Mac is an estimate of how much battery that app is costing you, not a reading from a meter. Several things feed into what an app really costs: how hard it works the processor, how much it uses the graphics chip, and how often it wakes the Mac from rest. A high figure means the app is a good suspect for a draining battery. It does not tell you the app is misbehaving, because a video export is supposed to cost a lot.

The trick to reading it is to separate a busy app from a wasteful one. This post shows what feeds the figure, where to see it, and how to tell the difference.

What goes into the figure

An app can spend power in three main ways.

The processor. Work that keeps the CPU busy costs power, and the more cores that are busy, the more it costs. This is the obvious one, and the one how to see which app is using the most CPU on a Mac covers.

The graphics chip. Video playback, games, big animations and web pages with moving graphics all use the GPU, which has its own power cost even when the processor looks calm.

Wake-ups. This is the one people miss. When nothing is happening, a Mac drops into a low-power state. Every time an app asks for attention, such as a timer firing or a script checking for new mail, the Mac has to wake up for a moment. One wake-up costs almost nothing. An app that wakes the Mac constantly keeps it from ever resting, and a process can show a near-zero CPU percentage while still costing real battery.

That is why CPU alone is an incomplete guide to the battery. Two apps can show the same low CPU figure, and one of them can cost more because it also keeps the graphics chip busy or keeps waking the Mac.

Where to see it on your Mac

You have two places that need no extra software.

Click the battery icon in the menu bar. If something has been using a lot of power, macOS lists it there under Using Significant Energy. That is a quick way to catch a single obvious culprit; when there is none, it says No Apps Using Significant Energy.

System Settings > Battery has graphs of Battery Level and Screen On Usage for the last 24 hours or the last 10 days. They tell you when the battery dropped fast, which helps you match a drain to what you were doing. Do not count on them to break the drain down by app.

For a ranked list of every app, you need a page that shows each app’s power next to the others. Foreman has a Power usage column in its Processes page, next to CPU, Memory, Disk, Network and GPU. Click the header to sort, and the heaviest apps come to the top. Each app’s helper processes are added into the app’s row, which matters for something like a browser, where the power is spread across a dozen helpers. How to find which app is draining your MacBook battery walks through the whole hunt.

Now versus over time: watt-hours

A live figure shows what an app is costing right now. Battery drain is about the total over an hour, and the two are not the same. An app that spikes for ten seconds and then goes quiet looks alarming at the moment you glance at it, and does very little over the afternoon. An app that sits at a modest, steady cost all day can empty the battery without ever looking dramatic.

The way to tell them apart is to look at a total. Foreman’s App History page shows, for each app, how long it has been open, its CPU time, disk read and written, network, and Energy in watt-hours. A watt-hour is a unit of energy, the same unit that battery capacity is quoted in, so it compares directly with what your battery holds. Sort by Energy and the app at the top is the one that has used the most since it opened.

Two limits are worth knowing, because they affect how you read it:

The totals run from when the app was opened. They last as long as the app stays open and are not kept after it quits. A browser you restarted an hour ago only shows that hour.
Foreman does not keep a long history. It cannot tell you what drained the battery last week.

So the useful habit is to check it at the end of a long unplugged session, with your usual apps still open, and look at who is at the top.

Reading the numbers sensibly

Here is how to decide whether a high figure is a problem.

Is the app doing something you asked for? An export, a render, a game, a video call and a screen recording all cost a lot, and should. The cost ends when the job ends. This is not a problem to fix; it is a reason to plug in.

Is it costing power while you are not using it? This is the real signal. An app sitting in the background with a high figure, while you work in something else, is spending your battery on nothing you can see. A browser tab playing a video in another window, a chat app in a busy loop and a sync client that never finishes are the usual cases.

Does the drain ease when you stop it? Quit or pause the suspect, then carry on as before for a while. If the Mac runs cooler and the battery percentage falls more slowly, you found it. If not, it was not the cause.

If the culprit is an app you need to keep open, you do not have to quit it. Foreman’s Efficiency Mode puts an app at background priority while it is in the background, and holds it to about a quarter of the processor time it would otherwise take, in short bursts. In front, or while it is playing sound, it runs at full speed. It is remembered per app. How much battery it saves depends on how busy the Mac is, and there is no fixed number, so treat it as something to try and then check against the Energy column. How to stop one app from slowing down everything else on your Mac explains when it fits.

Things that quietly raise the figure

A few causes come up again and again, and are worth checking before you blame a particular app:

Screen brightness and an external display. These are not per app, but they dominate the battery on many Macs. If an app tops the list by a small margin, the screen may be the bigger cost.
Indexing and photo analysis right after an update or a big import. These run for a while and then stop. Give it a day before chasing it.
Many tabs and web apps. Each can wake the Mac on a timer. Close what you are not reading.
Video calls. They use camera, microphone, network, processor and graphics together, so they top almost every list.

A high figure is a starting point. Match it to what you were doing, look at the watt-hours over a stretch of real use, and only then decide whether to quit the app, change its setting, or leave it alone.

Foreman is $12 once, free for 24 hours, if you want the Power usage column and App History in one place. The figures above are worth understanding even if you never use it: the menu bar battery list and System Settings > Battery cover the first look.