Battery life is probably the single biggest question surrounding the Apple Watch (after its full range of prices, of course). Now, we're finally getting an answer — Apple has just announced its first wearable will get about 18 hours of battery life over a normal day. CEO Tim Cook said that amount of time "works for most people."

Shortly after the event ended, Apple released more detailed specifications on just what sort of battery life you can expect when using the Apple Watch. For starters, it's worth noting that Apple says all of its tests were performed on the 38mm model; due to the larger size, owners of the 42mm model can expect longer battery life.

Owners of the 42mm model can expect longer battery life

Apple then broke its testing down into six categories: all-day battery life, talk time, audio playback, workout, watch, and power reserve. As mentioned in the keynote, the Apple Watch gets 18 hours of battery life — that was with the following usage patterns: "90 time checks, 90 notifications, 45 minutes of app use, and a 30-minute workout with music playback from Apple Watch via Bluetooth, over the course of 18 hours." It's hard to say without using the Watch in practice, but that sounds like pretty light-to-moderate usage. 45 minutes of app usage doesn't sound like a lot — but that's coming from a smartphone usage model, not a watch.

The talk time and audio playback tests are pretty self-explanatory: you'll get about 3 hours of battery when placing calls from the Apple Watch, and about 6.5 hours of music playback when paired with an iPhone using Bluetooth. It's possible to play music directly from the Apple Watch, but Apple didn't say how long you'd be able to do that. If you're thinking of using the Apple Watch as a dedicated fitness tracker, you'll get about 7 hours of usage — Apple says that's how long it'll last with the workout session active and the heart rate monitor turned on.

"You can continue to see the time for up to 72 hours."

Finally, Apple gave some details about more minimal usage that'll extend the Watch's life — if you're just checking the time (5 times an hour for 4 seconds each, under Apple's tests), the Apple Watch should last about 48 hours. And, as we heard in reports over the last month or so, there's a low power reserve mode. If the battery of your Watch gets too low, it'll automatically switch to power reserve mode. Apple seems to imply that the watch will last an additional 72 hours at that point: "If your battery gets too low, Apple Watch automatically switches into Power Reserve mode so you can continue to see the time for up to 72 hours." That's pretty impressive, if true, but we'll have to do some thorough testing to see exactly how this all plays out.

An Apple spokesperson confirmed to TechCrunch that the Watch battery can also be serviced to extend the wearable's lifespan. This is similar to the service already offered to iPhone, iPad, iPod, and MacBook owners. No price has been announced, although out of warranty battery service on an iPod costs between $49 and $79 in the US.

Earlier this year, reports surfaced indicating that the Apple Watch battery life would be quite similar to most other smartwatches on the market — estimates indicated it could between 2.5 and 4 hours of heavy use. But since most users aren't constantly interacting with a smartwatch for extended periods of time, Apple was hopeful that would be enough to get it through the day. That said, battery life was reportedly still a big concern for Apple, and apparently the company has been working hard to improve it — another report the week before today's event indicated that the watch would get closer to five hours of constant use and potentially last into a second day.

Update Mar 10, 12:27 pm: Added battery service information and confirmation to TechCrunch.

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