What does an all-day battery life of 18 hours really consist of? That's what Apple's promising it's debut smartwatch will offer. Thankfully, it has also detailed a bunch of other power-draining use cases to allay / confirm (delete as appropriate) any battery life fears. This typical use battery life apparently consisted of:
"90 time checks, 90 notifications, 45 minutes of app use, and a 30-minute workout with music playback from Apple Watch via Bluetooth"
Apple notes that this was a preproduction model from this month, and even offers all the other reasons why you might not get the same numbers, stating that "Battery life varies by use, configuration, and many other factors; actual results will vary." Placing a call through the watch will allow you to talk to your wrist for just three hours, while at the opposite end of the use spectrum, just wanting to see the time on the display will mean the watch can eke out up to 78 hours of use -- entailing four time checks every hour, but nothing else.
Apple's listed its results and testing methods here, but here's the quick and easy version:
Audio Playback Test: Up to 6.5 hours
Workout Test (with heart rate sensor): Up to 7 hours
Charge Time: About 1.5 hours to 80%, about 2.5 hours to 100%