How to see how many watts your Mac is using
How to measure a Mac's power draw in watts with powermetrics, how to read charging power from ioreg, and what typical figures look like.
How do I see Mac power usage in watts?
powermetrics, built into macOS, reports CPU, GPU and package power in milliwatts:
sudo powermetrics --samplers cpu_power,gpu_power -i 1000 -n 5It needs an administrator password and prints a sample each second.
How do I see charging power?
ioreg lists battery voltage and current; multiply them for watts going into the battery:
ioreg -rn AppleSmartBattery | grep -E '"(Voltage|Amperage)" ='What uses the most power on a Mac?
The display, then the processor and GPU under load. Per app, Energy Impact ranks them.
Common questions
How many watts does a MacBook Air use?
Only a few watts at light use and much more under load. powermetrics shows yours live.
Does Activity Monitor show watts?
No. Energy Impact is a relative score. powermetrics in Terminal reports milliwatts.