of one CPU core
What the app itself uses with all nine readings on. Turning readings on or off does not change it.
Measured 15 September 2026
How much MemPressure costs to run
One run, one machine, Apple's own tool, and the table as it came out. Nothing here is rounded up or estimated.
With it, or without it
Whole-machine power was 183 mW with the app quit and 183 mW with everything running, three spinning cogs included. The cog spins for free.
Can't phone home, not won't
The app runs in the App Store sandbox with no network entitlement, so macOS itself stops it from connecting anywhere. No account, no analytics, no helper process.
Setup
One machine, left alone.
MacBook Air, Apple M4, macOS 26. MemPressure 1.5.0. Measured with powermetrics sampling tasks, CPU power and GPU power every 10 seconds, 25 minutes per condition, on mains power with the display kept awake. Only samples taken after at least 30 seconds without keyboard or trackpad input were kept: 590 of 598.
App quitThe baseline. Everything else is read against this row.
Two static barsPressure and CPU as classic bars. Nothing moves between polls.
One spinning cogCPU as a cog that turns with load. The only animated widget.
All nine readings, three cogsThe heaviest configuration the app allows.
MachineMacBook Air, model identifier Mac16,12, on mains power, display awake.
SamplesEvery 10 seconds for 25 minutes per condition. 590 of 598 taken while idle.
Results
Four conditions, one baseline.
Median and 95th percentile across the samples of each run. WindowServer is shown as its difference from the baseline.
| Condition | MemPressure CPU ms/s, median / p95 |
Energy Impact median / p95 |
Wakeups per second |
WindowServer vs quit, ms/s |
GPU mW |
Whole machine mW |
|---|---|---|---|---|---|---|
| App quit | 0 | 56.5 | 183 | |||
| Two static bars | 4.32 / 4.46 | 0.25 / 0.29 | 3.0 | +4.8 | 56.0 | 183 |
| One spinning cog | 4.29 / 4.45 | 0.25 / 0.29 | 3.0 | +4.5 | 56.0 | 183 |
| All nine readings, three cogs | 4.19 / 4.40 | 0.26 / 0.29 | 3.0 | +4.8 | 57.0 | 184 |
MemPressure CPU
Milliseconds of CPU time the process used per second of wall clock. 4.3 ms in a second is 0.43% of one core. The 95th percentile is the value that 95% of samples stayed under.
Energy Impact
Apple's composite of CPU, GPU, wakeups and other costs, on the scale Activity Monitor uses in its Energy tab. It is the same figure Activity Monitor shows for the app.
WindowServer
The compositor draws the menu bar, so part of the cost of any menu bar widget lands there. This column is WindowServer's CPU time in each run minus its CPU time with the app quit. It is the same for a static bar and a spinning cog, so the animation costs nothing measurable. Counting it, the whole cost of the app is about 0.9% of one core.
Whole machine
Power drawn by the chip package, averaged over the run. It is identical with the app quit and with everything on, which means the app's draw sits under what the tool can resolve at that level.
What this does not tell you
One machine, one build. Resident memory is about 70 MB, mostly framework overhead, and is not part of this measurement. Numbers for each new release will be added here.
Check it yourself
Two things you can verify in a minute.
Open Activity Monitor, choose the Energy tab, and sort by Energy Impact. MemPressure sits near the bottom, under most of what macOS runs on its own.
For the network claim, ask macOS what the app is allowed to do:
codesign -d --entitlements - /Applications/MemPressure.appLook for com.apple.security.app-sandbox set to true, and no key beginning com.apple.security.network. Without one, the system refuses any connection the app might try to make.