The battery-saving mode turns off the more demanding features such as AoD, heart rate notifications, arrhythmia tracking, heart rate and blood oxygen measurements. Workout reminders are also turned off.
Interestingly enough, if there's no iPhone connected to the watch nearby, it will turn off Wi-Fi, and cellular connections. Incoming calls and notifications are also disabled. Surely, if you need a certain app that requires data or Wi-Fi connection, the system will re-enable those. And if the watch stays within the phone's connection range, it will postpone notifications and deliver them every hour.
Of course, the overall performance of the watch in the new battery-saving mode will also be reduced, so animations and navigation as a whole won't feel as smooth.
