The quit receipt

Updated 23 August 2026 · every wording quoted here is the text the app actually shows, taken from its own strings file. Who measures this.

Before you quit an app, WattMate names what it is worth: not a score, but a change in how long the charge lasts. Two minutes after you actually quit it, the Mac is measured again and the app prints what really happened. Sometimes what it prints is that nothing can be claimed.

What it looks like

The projection is a pair of times rather than a percentage: 2h 21m now, 2h 36m without it. That framing is deliberate. Minutes are the thing you were actually asking about, and unlike a score they can be checked afterwards.

Then the check. Two minutes after the app is gone, the machine is measured again and the result goes next to the promise. If the load moved for other reasons in those two minutes, the app says so in as many words: "Over those two minutes the load changed for other reasons too, so the gain couldn't be measured honestly. It isn't counted toward your savings."

Why the refusals matter more than the numbers

A tool that reports a win every time is not measuring anything. Most of the work here went into knowing when to say nothing, and the app has a different sentence for each reason.

Situation	What the app says
Not enough samples yet	"The app list is ready. Naming the minutes needs a few more samples."
This Mac is still unmeasured	"Until we've measured this Mac, we can't say how much longer the charge would last."
Apps are not the problem	"The rest is screen and system — the backlight and services, and that can't be quit."
The app went idle	"The app has used nothing for the last few minutes — there is nothing to quit."
Plugged in	"On mains the charge is not being spent, so there is nothing to measure. Numbers return when you unplug."
The app refused to close	"It's asking you to save files — switch to it and answer the prompt."
No machine to measure	"Every number here would be a zero, and a zero we cannot stand behind is worse than no number at all."

That last one is what a virtual machine gets. The per-process energy counter exists there and returns zero, so the app declines the whole screen rather than showing a column of noughts.

The promise is deliberately the low end

Under the information circle: "We show the low end of the gain: the Mac's own power isn't knowable to the watt." A range would be honest and useless; the bottom of the range is honest and actionable. If the number turns out generous, you notice. If it turns out shy, you got more than promised.

Two more rules come from the same reasoning. A projection appears only when quitting would stretch the remaining charge by a real margin rather than a rounding error. And the minutes on different rows cannot be added: "An app's minutes answer one question: what if I quit this one, now." Quitting two apps does not give you the sum, because the second one inherits a machine the first one already changed.

What this does not do

The re-measurement watches the whole machine, not the one app, because nothing in macOS reports the machine's power per process after the process is gone. Across 273 events where nothing was quit at all, the managed pool still drifted by about three watts either way, while a typical row promises between half a watt and one and a half. Any single promise would "confirm itself" a fifth of the time by chance.

So there is no verified badge on one quit, and there will not be. The app requires a much larger movement before it will show a measured result at all, and stays quiet otherwise. There is also no success rate on this page: a percentage of promises kept would need a corpus we do not yet have, and inventing one would be the exact failure this feature exists to avoid.

Questions people ask

Why two minutes and not immediately?

Because the machine takes a moment to settle after an app disappears, and because the measurement is built from windows rather than instants. Reading it too early would measure the closing, not the absence.

What if I quit the app myself, outside WattMate?

The energy already measured stays on the row, the row dims and gets a quiet "quit" mark, and the result is recorded. The "couldn't isolate" wording belongs to the path that starts with our own button, because only there does the app know exactly when the quit happened.

Does it work while charging?

No, and that is not a limitation to work around: on mains the battery is not paying for anything, so there are no minutes to give back. The numbers return when you unplug.

Can I trust a number that low?

The low end is the point. What makes it checkable is the second half: the app comes back two minutes later and tells you whether the machine agreed, including when it has to say the effect could not be separated from everything else.