How many watts is your Mac using right now?

Updated 23 August 2026 · the command below was run in zsh and bash, on battery and on the charger, before this page went up. Who measures this.

Your battery reports the current flowing through it and the voltage across it. Multiply them and you have watts. No password, no download, and one catch worth knowing before you look at the number.

The command

B=$(ioreg -rn AppleSmartBattery -a); A=$(printf %s "$B" | plutil -extract 0.Amperage raw -o - -); V=$(printf %s "$B" | plutil -extract 0.Voltage raw -o - -); E=$(printf %s "$B" | plutil -extract 0.ExternalConnected raw -o - -); awk -v a="$A" -v v="$V" -v e="$E" 'BEGIN{w=(a<0?-a:a)*v/1000000; printf "%s: %.1f W\n", (e=="true"?"On the charger, going INTO the battery":"On battery, the Mac is drawing"), w}'

It uses plutil and awk, both of which ship with macOS. Nothing is written to disk and nothing leaves the machine.

The catch: it breaks when it works

Run the usual version of this without the -a flag and on battery you get Amperage = 18446744073709550716. That is not a fault. Current out of the battery is negative, the raw property is unsigned, and the formatter prints the wraparound. Plug the charger in and the same field prints something tidy like 3195, which is the current going into the pack.

So the reading looks broken exactly when it is the answer, and looks healthy exactly when it answers a different question. The -a flag fixes it by asking for the property list instead of the formatted text: the same key that prints as 18446744073709543540 comes back as -8076.

On the charger the number is not your power use

Plugged in, what you measure is the charging current, and that says more about how empty the battery was than about what the Mac is doing. A machine drawing a modest amount while charging hard reads high; the same machine drawing the same amount with a full battery reads near zero. To measure spending, unplug.

Take more than one reading

The battery's gauge does not publish continuously. It updates in batches, tens of seconds apart, and the interval is not fixed. Two consecutive readings can return the same figure simply because nothing new was published in between, and a single snapshot can land on a spike that had nothing to do with what you were doing. Run it a few times over a couple of minutes before believing any one value.

What is a normal number?

Across 436 measured windows on two Apple silicon Macs, the draw ran from 6.74 W to 59.73 W, with a median of 23.82 W and the middle half between 15.76 and 31.95 W. The two machines' own averages sat three times apart, so treat that range as the span of possibility rather than a target. How many watts is my MacBook using has the full distribution and the method behind it.

Questions people ask

Why not use powermetrics?

It refuses without administrator rights: "powermetrics must be invoked as the superuser". It reports far more detail once you give it a password, but for a single question about watts, a command that needs no password is the better trade.

Does Activity Monitor show watts?

No. Its Energy Impact column is a relative score with no unit, which is why "Chrome: 42.3" cannot be compared to anything outside that window.

Why does the number jump between readings?

Because the machine's draw genuinely moves that much. The screen, background work and a single busy tab all land in the same figure, and the gauge publishes in batches rather than continuously. That is also why one reading cannot tell you what an app costs: for that you need the same measurement repeated with and without it.

Can I see this per app?

Not from the battery. It reports one current for the whole machine, so splitting it between apps takes a different measurement entirely, which is what WattMate does.