- IN watts the charger is putting out.
- OUT watts the laptop is using. Exact on battery; estimated while plugged in.
- NET IN minus OUT: what's left for the battery. Positive and it's filling; negative and the laptop is draining even though it's plugged in, which the state line says plainly: Plugged in · draining · 1h 20m left. NET is measured directly by the battery, so it's exact even when IN and OUT are estimates.
- Time to full or time left, from a five-minute average, refreshed every thirty seconds.
- Stored energy in watt-hours, voltage, health against design capacity, and cycle count.
- Thirty-minute graphs of charge, charger watts, laptop watts and voltage, kept across restarts.
- Hover any number for a two-sentence explanation in plain words.
Any Windows laptop with a battery: Windows 11 or Windows 10 from version 2004, Intel, AMD or Snapdragon, x64 or ARM64, two batteries included. Laptops whose firmware reports no charge rate (many HP consumer models ship with it off in the BIOS, so other tools show 0 W) get their watts from how fast the stored energy moves, with a "measuring" state instead of a fake zero. The plugged-in IN and OUT figures use the processor's own power meter, which Windows 11 exposes on Intel and AMD machines; elsewhere they show a dash with the reason on hover, and NET works everywhere.
Watt's Left is a free, open-source Windows app that shows, live, how many watts your charger is putting into your laptop battery and how many watts your laptop is drawing out, plus time left, stored energy, voltage and battery health. One small window. No account, no ads, no tracking, and it never touches the network. More at wattsleft.app.
Requirements: Windows 10 or 11, and a laptop with a battery. The Store package and the installer each carry everything they need, with nothing else to set up.
Windows itself only shows a percent. Watt's Left reads the battery hardware directly through
the Windows battery interface (IOCTL_BATTERY_QUERY_STATUS, which reports the rate in
milliwatts) four times a second; that rate is NET. While plugged in, the battery can't see what
the laptop itself is using, so Watt's Left reads the processor's power meter (the Energy Meter
performance counters, which Windows 11 exposes on Intel and AMD machines, no driver, no admin)
and adds what the rest of the machine was measured to cost while last on battery: that's OUT,
and OUT plus NET is IN. It needs a couple of minutes on battery once to learn the machine, and
keeps refining. The result is one small window that stays out of the way, plus the app in your
tray.
No network connections at all. Nothing is uploaded, and there is no account, no analytics, and no ads. Your settings and the last half hour of readings live in the app's own private folder on your machine, and they are removed when you uninstall. Full Privacy Policy.
I have literally no idea what you're talking about. Next question.
MIT. See LICENSE. Made by Aron Frishberg.