Test results: iPhone 4 battery life

As you know, Apple’s new iPhone 4 ( ) boasts a boatload of new features and improvements. One such improvement is increased battery life. Apple claims the new phone can outlast its predecessor by an hour in Internet use, two hours in talk time, and 10 hours of audio playback. Both the iPhone 3GS ( ) and iPhone 4 claim to hold enough juice to play up to 10 hours of video, and can last up to 300 hours in standby mode.

To get an idea of how the iPhone 4’s battery life compares to its predecessor in varied use, I borrowed a colleague’s year old 32GB iPhone 3GS and tested it and the iPhone 4 using a series of different tasks. The results show that the iPhone 4 does indeed last an appreciably longer time.

Test results

On both phones we set the screens to full brightness and rented a standard definition video (Shaft’s Big Score) from the iTunes Store’s 99-cent library, which took about 45 minutes for the phones to download over the office Wi-Fi network. We then played the 1 hour and 43 minute movie in widescreen mode.

Next, I downloaded the free Pandora ( ) application from the App Store over 3G and then surfed the Web while Pandora streamed music in the background. I did this for 30 minutes on the 3GS and then made a 14-minute phone call before the battery died. Total battery test time for the 3GS was 3 hours and 14 minutes.

On the iPhone 4, I was able to browse the Web with streamed musical accompaniment for 50 minutes, make a 30 minute phone call and watch another 44 minutes of Shaft’s Big Score before the new phone called it quits—4 hour and 32 minutes after testing began. And while the iPhone 4’s 40 percent longer battery life was truly impressive, I worried that the year-old 3GS’s battery had significantly less capacity than when purchased.

As I was set to post the story, Macworld Assistant Editor Lynn La mentioned to me that she’d purchased a new iPhone 3GS just two weeks ago. She graciously allowed me to take her phone for the day and I ran the tests again.

(All the iPhones tested in the article used iOS 4.)

With the iPhone 3GS’s fresh battery, I was able to do all of the tasks I’d done with the older 3GS, but with 14 minutes more talk time. In all, the new 3GS’s 3 hours and 28 minutes of battery life lasted a little more than 7 percent longer than the older 3GS I originally tested with. But the iPhone 4’s battery life was still 31 percent better than the fresh 3GS.

To see how long the iPhone 4 battery could last running two of its marquee features, I ran another test using the iPhone’s version of iMovie ( ) and FaceTime video calls. I alternated between the apps, first launching iMovie and capturing video from within the application, applying a theme and titles, exporting as a large movie and then watching the completed video. Next I placed and timed a FaceTime call between two iPhone 4 models. In this test, the iPhone 4 lasted just 2 hours and 21 minutes—capturing, manipulating, exporting and viewing 25 minutes of HD video and making 34 minutes of FaceTime calls.

Now, who wants to loan me their iPhone to test out Apple’s 300 hours of standby time claim?

[James Galbraith is Macworld’s lab director.]

Updated 7/2/10 at 7:40 a.m. PT with information about the iOS used for testing.