Energy Impact in Activity Monitor is a score for how much energy an app uses now, compared with other apps. Apple calls it “a relative measure”, where lower is better. It is not watts, and Apple gives no good or bad number. Here is what each column of the Energy tab means, and how to see energy in watts.
Open the Energy tab
- Open Activity Monitor. It is in the Utilities folder in Applications, or search for it with Spotlight.
- Click Energy at the top of the window.
- Click a column name to sort by it.
The columns
| Column | What it means |
|---|---|
| Energy Impact | A relative measure of the energy the app uses now. Lower is better |
| 12 hr Power | The average Energy Impact of the app in the last 12 hours, or since the Mac started. Only on Mac laptops |
| App Nap | If macOS has put the app in App Nap, which slows an app you cannot see |
| Preventing Sleep | If the app keeps the Mac from sleeping |
| Graphics Card | If the app needs the high-performance graphics card. Only on Macs with more than one |
| User | The user that runs the process |
Older versions of macOS had Avg Energy Impact, the average for the past 8 hours, and Requires High Perf GPU. Current versions have 12 hr Power and Graphics Card in their place.
The panel at the bottom
On a Mac laptop, the bottom of the Energy tab shows:
- the remaining charge
- the time until full, while the Mac charges
- the time on AC power, or on battery
- the time remaining
- a chart of the battery for the last 12 hours
Why Energy Impact is not watts
In a reply on Apple’s developer forums, an Apple engineer describes Energy Impact as an abstract value, not a specific measurement unit. macOS combines the processor, storage, network and other activity of the app, with a weight for each. The weights differ between Mac models, so a score of 20 on one Mac is not the same energy as 20 on another.
This changes how you read the list.
- Compare apps on the same Mac. The order of the list is the useful part.
- Do not add the scores to get the total. The display, the graphics, the radios and a phone charging from a port are not in the list. On one MacBook at light load we measured about 15 W for the whole Mac, and 0.5 W of it was the processor energy of all apps.
How to read the list
- Sort by 12 hr Power. An app near the top that you did not use for hours runs in the background. Check its settings, or quit it.
- Look at Preventing Sleep. A Yes keeps the Mac awake. If the battery drains overnight, start here.
- Look at App Nap. macOS slows an app in App Nap. An app you cannot see that shows No is not slowed.
- Group the helpers. A browser runs many processes. Click the arrow next to the browser to see its tabs and helpers together.
Energy in Terminal
Two commands show energy figures.
| Command | What it shows |
|---|---|
top -stats pid,command,cpu,power -o power |
A POWER column for each process, sorted with the largest first. Mozilla’s documentation says this is the same score as Energy Impact |
sudo powermetrics -i 5000 -n 1 |
Estimates of the power of the processor, the graphics and other parts, for one 5-second sample. It needs an administrator password |
The powermetrics manual says its power values are estimated and may be inaccurate.
See energy in watts, over time
Activity Monitor keeps 12 hours at most, shows scores and not watts, and leaves out the display and the ports.
BatteryBud is a battery monitor for Mac. From version 1.3.0 it has Power flow on MacBooks, a map of where the power goes. It has two modes.
- Measured shows the processor energy macOS records for each app, in watts and watt-hours. Everything else, the display, the graphics, the radios and macOS itself, is System.
- Estimated takes the draw of the Mac from the battery controller, leaves the devices and the charging as measured, and splits the rest between the apps and macOS by the same score that Activity Monitor ranks by. It marks those figures as estimates.
The map also shows each device that charges from a port, in watts. It covers the last 24 hours, 7 days, 30 days or 12 months, or the time since you unplugged. See what is draining your Mac battery.