The Apple Watch has never been known for having long battery life. Case in point: Apple never budged from the 18-hour battery life estimate until it launched the Apple Watch Ultra. In 2022, the company introduced a new Low Power Mode when it launched the Ultra, and now, it has extended the time between charges for Apple Watches using watchOS 9 and later.
Previously, the Apple Watch had a Power Reserve mode, which shut off any functions aside from your ability to tell time and turned your smartwatch into a normal watch until you could get it to a charger. This mode is different — it’s more like the iPhone’s Low Power Mode. When enabled, you’ll still be able to use your Apple Watch, but certain power-hungry features will be turned off or limited to conserve the battery.
On the Apple Watch, Low Power Mode disables the always-on display and limits sensor readings like background heart rate and blood oxygen monitoring. (You should be aware that it also disables irregular heart rhythm notifications as well as high and low heart rate notifications.)