What macOS shows on its own
The battery menu lists apps “using significant energy”, and Activity Monitor’s Energy tab shows an energy impact score per app. Neither gives you watts, and neither stays on screen.
How Multimeter shows it
- On Apple silicon MacBooks, Multimeter reads the system power figure the battery controller reports, plugged in or not.
- On Intel MacBooks it works it out from battery current and voltage, which only works while running on battery.
- It reads every 5 seconds on power and about every 10 on battery (slower again in Low Power Mode), and pauses while the displays sleep.
- The range scales to the recent peak unless you set one, so a Sparkline shows your normal and your spikes at the same time.
Set it up
- Choose Add Meter… and pick Power Draw.
- Pick a face: LCD Readout for the number, Sparkline to see spikes over the last few minutes.
- Set a fixed range in Customize if you want the needle to mean the same thing every day (for example 0 to 40 W).
Every face works with every source it lists. See all 13 faces running live.
How long will the battery last at this draw?
Divide the battery’s energy by the draw: hours left ≈ battery watt-hours × charge left ÷ watts. A battery rated at 70 Wh, at 60% and drawing 7 W, has roughly 70 × 0.6 ÷ 7 = 6 hours. Your Mac’s battery rating is on Apple’s tech specs page for your model.
That’s why the watts meter is worth watching: halving the draw doubles the time left. The Time Until face shows macOS’s own estimate, which moves the same way.
Limits
Desktop Macs without a battery don’t report power draw, and the meter says so.
Questions
How many watts does a MacBook use?
It depends on the model and what it’s doing. Watch the Power Draw meter for a day: light work, a video call and a build will each show you a different number for your own Mac.
Is the watts reading the same as the charger’s wattage?
No. The charger rating is the most it can supply. The meter shows what the Mac is using right now, which is usually far less.