Watts per app

Updated 30 September 2026 · the wordings quoted here are the app's own strings. Who measures this.

WattMate shows every app in watts, not a unitless score, with helper processes folded into one row and system daemons kept separate. Each figure is the Mac's battery draw minus the floor for the screen and staying awake, split by each app's share of the chip counters. On battery, most rows also show minutes back from quitting.

How are processes grouped into one row per app?

Chrome runs as sixteen to forty processes depending on the day. Activity Monitor shows you all of them; the list here shows one row called Chrome, built by walking each process back to its application bundle. The same folding puts an iOS Simulator and every daemon it starts into a single row you can close in one action.

System daemons do not join the ranking at all. They go into one bucket labelled as system processes, because a list you can act on should not be padded with things you cannot quit. The energy still counts toward the machine's total, it just does not pretend to be a suggestion.

An app you have already quit stays on the list with the watts it spent, dimmed and marked as quit. Those watts were measured and they happened; moving them into an anonymous "system" row afterwards would quietly rewrite the last few minutes.

What does the number on each row mean?

The counters the app reads live on the chip, and a chip watt is not a battery watt: the pack pays roughly two and a half times more. So the figure on a row is not a raw counter reading. It is the machine's actual battery draw, minus the floor that the screen and simply being awake consume, split between apps by their share of those counters. The measurement behind that is written out separately, including why the obvious approach loses four fifths of the work on an idle Mac.

The popup and the statistics window deliberately show different averages: a short recent horizon in the popup, the whole session in the window. Numbers seen side by side will not match, and neither is wrong.

Below half a watt the row prints "less than" rather than rounding to zero. A zero would say the app spends nothing, and the row exists precisely because it spends something.

When there is no list at all

One case, and the app says so outright rather than showing an empty table.

On a machine without the counter, usually a virtual machine: "WattMate reads a per-process energy counter from the kernel, and this Mac does not have one. Every number here would be a zero, and a zero we cannot stand behind is worse than no number at all."

Why does the list show watts but no minutes?

The app list appears within seconds. The minutes take longer, and the app is explicit about the wait: "The app list is ready. Naming the minutes needs a few more samples."

Its own methodology page puts a number on that: half the time the first figure arrives within three minutes, sometimes much longer, "which is why we never promise a countdown". After the Mac wakes from sleep the wait starts over, because the measurement is built from a continuous run of windows and sleep breaks the run.

There is a second reason minutes can be missing while watts are present. Converting watts into minutes needs the machine's floor, and until that has been measured on your particular Mac the app names the app but not the gain: "Until we've measured this Mac, we can't say how much longer the charge would last."

Questions people ask

Why only three apps in the popup?

Because a menu bar panel is for a decision, not for a table. The full ranking is one click away in the statistics window, where it expands to every row.

Does it show watts while plugged in?

The list is there, but without minutes: on mains the battery is not paying for anything, so there is nothing to give back by quitting.

Why does WattMate list itself?

Because measuring costs something, and hiding our own cost while showing everyone else's would be the one row you cannot check. It is listed and not offered for quitting, since quitting the app that draws the list is not a suggestion worth making.

How often does the list update?

On the completion of a measurement window rather than every second, and only while a window is open. "Live" here means current, not animated.