How to enable Power Reserve mode on your Apple WatchSave battery life on your Apple Watch by putting it in Power Reserve mode.
If you still want to see the time on your Apple Watch but have no need for its other features, consider putting it in Power Reserve mode to save a bit of battery life. When your watch is in this mode, all features are disabled save for the current time, which is displayed in green.
How to enable Power Reserve mode on your Apple Watch
Make sure your Apple Watch is displaying a watch face.
Swipe up from the bottom of the screen to activate Control Center.
Tap on the Battery Percentage reading.
Tap the Power Reserve button.
Tap Proceed.
You can exit Power Reserve mode at any time by pressing and holding on the Side Button. This will restart your watch, so expect to wait 0:30-2:00, depending on your model.
Questions?
Let us know below.
...
Source:
How to enable Power Reserve mode on your Apple Watch