Feature · 電流
Where your watts go,adapter, system, battery.
Three numbers macOS never shows side by side: what the charger delivers, what reaches the battery, and what your Mac draws. Unplugged, that last number is your discharge rate. No estimate. The actual reading.
Why it matters
A percentage can't tell you why it's falling. Watts can. Once you see your 96 W charger delivering 38 W through a bad cable, or the system eating everything the adapter sends, the mystery is over.
Three numbers that explain everything
Battery questions usually reduce to one of three readings, and macOS exposes none of them in a place you'd find. Power flow puts all three in a single panel:
- Adapter in. What your charger is actually delivering right now, next to its rated wattage. A 96 W brick delivering 38 W is the answer to "why is this charging so slowly", usually a cable, a hub, or a port that negotiated down.
- System draw. What the Mac itself consumes. On battery, this is your discharge rate, which makes it the most honest predictor of runtime you can look at.
- Charging. The share reaching the cells. During heavy work this can be near zero even while plugged in: the system is eating everything the adapter sends.
Reading the panel
The rows run top to bottom: adapter, system, charging. When adapter in exceeds system draw, the surplus reaches the cells and the bottom row shows the charging wattage with its arrow pointing up. When system draw exceeds the adapter, the battery supplements the charger: you're on wall power and still losing charge, which the panel labels explicitly instead of leaving you to work it out from a shrinking percentage.
Unplugged, the adapter row disappears and system draw becomes the whole story. Pair it with the app energy panel to attach a name to a spike, and see watts in / watts out for the underlying terminology.
Where the numbers come from
IOKit's power telemetry, read directly from the SMC on Apple Silicon, the same source Apple's own tooling uses. No estimation, no sampling heuristics, no network calls. When a reading isn't available on your hardware, the row hides rather than showing an invented number.
Frequently asked.
- Why does my 96 W charger only deliver 60 W?
- Charging wattage is negotiated between the Mac, the cable, and the adapter. A cable rated below 100 W, a hub in the middle, or a nearly full battery all cap the delivered wattage. Power flow shows the negotiated figure next to the rated one so the gap is visible.
- Can the battery drain while plugged in?
- Yes. Under sustained heavy load the system can draw more than the adapter supplies, and the battery covers the shortfall. Power flow labels that state explicitly rather than leaving you to infer it.
- Does this work on Intel Macs?
- Partly. Apple Silicon exposes full power telemetry; Intel Macs report a smaller subset, so some rows may be unavailable. Sensei hides what it can't read instead of guessing.