Perhaps the biggest surprise in our iPhone 4S testing was its battery life. We suspected that something unusual was going on when Apple published its initial iPhone 4S battery life estimates, which oddly showed the new device improving in 3G talk time, standing still in 3G Internet use, and falling behind in both standby time and Wi-Fi Internet use. How could the new device improve or stand still in some categories and fall short in others that were seemingly related? After three days of non-stop testing, we had a clear answer: the iPhone 4S is generally more power hungry than the iPhone 4, and Apple has only made the slightest capacity improvement to the iPhone 4Ss battery. Moreover, whereas Apple underpromised with the iPhone 4s battery estimates, it comes closer to overpromising with the iPhone 4S.
Cellular Data: Apple promises up to 6 hours of 3G Internet use, equivalent to its promise for the iPhone 4. Whereas our AT&T iPhone 4 previously surpassed Apples estimate with a 6 hour and 47 minute run time, all of the iPhone 4S units we tested fell at least a little short: each with signal strength in the 3- to 4-bar range, our AT&T iPhone 4S achieved a 5:54 run time, while the Verizon iPhone 4S pulled off a virtually equivalent 5:53, and the Sprint iPhone 4S fell markedly behind at 5:23. The good news here is that the iPhone 4S essentially matches what Apple claims, but it drains more power than last years model. Moreover, we didnt see any actual download speed improvements over the three cellular networks, so its not as if users will be able to get more done over less time. Sprints poor battery performance was compounded by its slow data speeds, suggesting that users of this network will get hit with the double whammy of sluggish performance and lower longevity. Its also noteworthy that neither Verizon nor Sprint allows cellular data to be used when making phone calls, a feature thats only offered by AT&T.
Wi-Fi Data: Apple promises up to 9 hours of Wi-Fi Internet use, down from 10 hours on the iPhone 4, which notably had fallen well short of the companys estimate during our real world testing last year. Whereas the iPhone 4 previously ran for 8 hours and 35 minutes on a mixed 802.11b/g/n network, our iPhone 4S achieved exactly 8 hours and 30 minutes of run time, which is to say that it still fell a little behind Apples estimates. (Note that we retested a 16-month-old iPhone 4 on iOS 5.0; even with its battery weakened from more than a year of daily usage, it still achieved a remarkable 8 hour, 18 minute run time.)
Cellular Calling: Apple now promises up to 8 hours of 3G calling time with the iPhone 4S, up from 7 on the iPhone 4. Last year, our AT&T iPhone 4 ran for 7 hours and 6 minutes with 3G and Wi-Fi on, adding only a little extra time if Wi-Fi was off. Apple does appear to have improved the iPhone 4Ss cellular efficiency, at least on two networks. Our AT&T iPhone 4S achieved a 7 hour and 16 minute run time with 3G and Wi-Fi on, while the Verizon iPhone 4S actually ran for 8 hours and 27 minutes, both superior to our prior results on the iPhone 4. By contrast, the Sprint iPhone 4S turned in an amazingly weak 6 hours and 27 minutestwo hours less than the Verizon iPhone. Again, all three of the devices reported between 3 and 4 bars of service during testing, though the Verizon phone notably showed four bars the most often.
Its worth noting that Apple has dropped the promised standby time from 300 hours on the iPhone 4 down to 200 hours on the iPhone 4S, while promising the same 14 hours of 2G/EDGE calling time. However, the iPhone 4Ss settings menus currently do not include any conspicuous way to switch back to EDGE on the AT&T iPhone 4S, a feature that was previously on the GSM iPhone 4, 3GS, and 3G, but not on the CDMA iPhone 4. Its unclear as to whether this feature will be re-enabled in a later iOS 5 update for AT&T devices.
Audio: Apple promises up to 40 hours of audio playback with the device at 50% volume and its screen mostly off, equivalent to its claims for the iPhone 4. While the iPhone 4 blew past this estimate with a run time of 52 hours and 45 minutes, the iPhone 4S only barely beat Apples claim with a time of 41 hours and 20 minutesbetter than the companys promise, but well below what we saw last year. Incidentally, the iPhone 4Ss audio sounded great through the highest-end headphones, speakers, and wireless systems we tested it with.
Video: Apple promises up to 10 hours of video playback with the screen at 50% brightness and the volume at 50%, the same as for the iPhone 4. While the iPhone 4 easily surpassed that number with an 11 hour, 14 minute performance, our iPhone 4S tested out at 10 hours and 32 minutes running the same videos under the same testing conditionsonce again, lower than the iPhone 4, but slightly above Apples estimate.
FaceTime: Once again, Apple makes no promises as to the iPhone 4Ss battery life for FaceTime video calling over Wi-Fi. Our test of the iPhone 4 last year showed battery loss of 30% per hour, or 3 hours and 10 minutes of total battery life. Under the same testing conditions, the iPhone 4S turned in an almost identical FaceTime run time of 3 hours and 15 minutesever so slightly better.
1080p Video Recording: Last year, the iPhone 4 was able to record 720p movies for 3 hours and 3 minutes before its battery ran out. The iPhone 4S was able to record 1080p movies for a much shorter periodonly 2 hours and 20 minutesthough its worth noting that its actually capturing more than twice the amount of data, such that an empty 16GB iPhone 4S will run out of capacity after roughly an hour and twenty minutes of recording at that resolution. It would be helpful for Apple to include a resolution setting option, particularly if it might reduce both capacity and battery drain.