macOS says an app is "Using Significant Energy"

Updated 18 August 2026 · watt figures measured across 436 windows on one MacBook Pro (Mac15,10, M3 Max, macOS 26.5.2), 16–18 August 2026

Short version: the battery menu names an app, and that is the entire message. It doesn't say how much energy, or since when, or whether the app is still doing it. We can't tell you the threshold either — we have never measured it, and we'd rather say so than invent a number. What we have measured is the reason the warning so often looks wrong: by the time you open Activity Monitor to check, the busy stretch is frequently over.

What the menu tells you, and what it withholds

The number nobody prints — including us

Every page you'll find on this phrase describes the warning and moves on. That's not laziness on their part: there is no published figure to quote. The honest position is to say what's missing rather than to fill the gap with an estimate, so here is ours, plainly.

We do not know at how many watts an app joins that list. Not approximately, not within a range. WattMate measures watts per app; it does not watch the contents of the system menu, so we have nothing to correlate against — no pairing between "this app was drawing X watts" and "this app appeared in the list". Zero measurements, not a weak result.

The run that would close it is specific and unglamorous: record what the battery menu lists, on a fixed interval, alongside the per-app watt measurement, on the same machine over the same period. Until someone does that, "significant energy starts at N watts" is a sentence nobody on the internet has earned — us included.

Why Activity Monitor disagrees with the menu

This is the part we can measure, and it explains most of the frustration. On the Mac we measured, draw moved in large steps over short intervals. Across 435 consecutive pairs of windows on that MacBook Pro:

The largest drop we recorded took 27.1 W off the machine between one window and the next. That is not a subtle change. Windows that heavy are the exception rather than the rule:

So the sequence people describe — the menu names an app, you open Activity Monitor, the app is sitting near the bottom of the list looking innocent — is exactly what you would expect from a machine whose draw can shed twenty-odd watts inside a minute and a half. Neither display is lying to you. They are describing different moments, and only one of them is the moment you cared about.

What we can't say: that any of those drops was the app the menu named. We never recorded the menu, so that link is unmeasured, and stating it would be exactly the invention this page is arguing against. What the numbers do establish is the shape: bursts of this size happen, and they end fast.

What to do right now

Click the battery icon in the menu bar — the apps are listed there, under the heading about significant energy use. Then open Activity Monitor → Energy and sort by Energy Impact. If the named app is at the top, you have your answer while it's still true, and quitting it is a reasonable move. If it isn't at the top, don't conclude the Mac was wrong: you arrived after the fact, which is the normal case rather than the strange one.

One caution about that column. Energy Impact is a number without a unit — it is not watts, not percent, and not comparable to anything outside that window. It ranks; it doesn't measure. So "how much does this app actually use" is a question Activity Monitor structurally cannot answer: a rank tells you the order, not the cost. Answering it takes watts, which is why we measured a browser that way instead of reading its rank: what Chrome actually costs.

The catch: you have to be measuring before you look

Every tool described so far, including the battery menu, only starts telling you something when you open it. A burst that has already ended left no record anywhere you can reach. That's the whole problem in one sentence: the evidence expires before the person arrives.

This is what WattMate is for, and it is a modest claim rather than a grand one. It measures continuously in the background — every app, in watts, window after window — so when the menu names something, the answer to "what was it doing, and how much did it cost" already exists rather than having to be reconstructed. It also puts a number on the thing the menu implies but never states: what quitting that app is worth, in minutes of battery, on your machine under your load.

The resolution has a floor, and it's worth naming: our windows are about 90 seconds long. We cannot tell you how long a burst shorter than a window lasted — we have no instrument that would know. We can tell you that ninety seconds later it was gone, which happens to be the thing that matters when the menu and the monitor disagree.

Questions people ask

What does "Using Significant Energy" actually mean?

That macOS considers the named app to be among the notable consumers on the machine at some recent point. The wording is the whole specification — no figure, no window, no timestamp accompanies it. It's a pointer to an app, not a measurement of one.

How much energy counts as "significant"?

We don't know, and we're not going to guess. We have taken no measurement that connects a watt figure to an app appearing on that list, because the app doesn't observe the list. Anyone quoting you a watt threshold for this is doing so without evidence.

The menu names an app, but Activity Monitor shows it near the bottom. Which one is wrong?

Most likely neither. On the Mac we measured, the five largest drops between neighbouring windows of about 90 seconds were 27.1, 25.1, 22.7, 19.6 and 17.5 W. A burst that has already ended looks like innocence in a live display.

Should I quit the app it names?

If it's still at the top of Activity Monitor's Energy list, that's a reasonable move. In general, though, quitting apps buys less than people expect — we measured that separately: does quitting apps actually save battery?

It names the same app every day. Is that app the problem?

Being named repeatedly means it gets busy repeatedly; it doesn't tell you what the total costs you. For four apps that show up in these lists constantly, we measured the actual figures rather than guessing: Chrome, Xcode, Slack and Spotify — and some of them cost far less than their reputation suggests.

Does the warning mean something is wrong with my Mac?

Nothing on that list indicates a fault. It reports activity, and activity is what a computer does. It becomes worth acting on when your battery is going somewhere you didn't intend — which is a question about watts and minutes, not about the presence of a name in a menu.

What these numbers do and don't prove

One machine, one workload, two days. Every watt figure here comes from a single MacBook Pro (M3 Max) under a developer's load between 16 and 18 August 2026. A different Mac, or the same Mac used differently, would produce different steps and a different share of heavy windows. Take the shape as the finding — large changes from one window of about 90 seconds to the next — and the exact figures as one example of it.

Nothing here measures the macOS threshold. Repeating it because it is the most likely thing to be misread: these numbers describe how fast a Mac's draw moves, not how macOS decides what to list. The two are placed side by side on this page because the first explains the frustration, not because we have connected them.

Ninety seconds is our floor. Anything shorter than a window is invisible to us. Claims about what happened over a handful of seconds — from us or anyone else without a faster instrument — aren't measurements.

Related: what Chrome actually costs, measured on two Macs · Xcode: the most expensive app on that machine · does quitting apps actually save battery?