In June 2015, tests of Apple’s iOS 9 beta showed that Low Power Mode reduced processor performance to save battery power. MacRumors published Geekbench 3 results on June 25 showing lower scores on an iPhone 6 Plus and an iPhone 5s when the mode was enabled.
Apple had previewed iOS 9 on June 8, with battery improvements among its features. The benchmark results described prerelease software, so they were evidence of the beta’s behavior rather than a fixed performance penalty for every later iPhone.
The battery life promise
Apple’s announcement distinguished general iOS 9 battery optimization from Low Power Mode. The operating system’s broader improvements promised an additional hour of use for a typical user. That hour was not the stated benefit of Low Power Mode alone.
Apple’s iOS 9 release notes described Low Power Mode as optimizing device performance to extend battery life by up to an additional three hours. These were upper-limit claims, not a guarantee of the same extra runtime under every workload.
The benchmark results
MacRumors reported that the iPhone 6 Plus scored 1,606 in Geekbench 3’s single-core test and 2,891 in its multi-core test with Low Power Mode off. With it on, the scores fell to 1,019 and 1,751, respectively. The comparison showed a substantial processor-performance tradeoff in that beta.
The iPhone 5s showed a similar pattern. Its single-core and multi-core scores fell from 1,386 and 2,511 to 816 and 1,405. MacRumors characterized the reduction as about 40 percent, and AppleInsider’s contemporaneous coverage emphasized that the tests used beta software.
What the mode changed
In the iOS 9 beta, users could enable Low Power Mode in the Battery section of Settings. Low-battery prompts at 20 percent and 10 percent also offered a shortcut. A yellow battery icon indicated that the mode was active.
The mode reduced processor performance and background activity, including Mail fetch and Background App Refresh. Contemporary reporting also described disabled motion effects and animated wallpapers. The benchmark scores measured processor performance; they did not establish a particular frame-rate reduction for every game.
The public release
Apple subsequently announced that iOS 9 would be available on September 16, 2015. Low Power Mode remained part of the release’s battery-saving features. The original beta tests captured the central tradeoff: reduced activity and performance in exchange for longer use between charges.
Updated October 2026: Corrected the battery-life claim and attributed the historical beta benchmarks. The original article was published in June 2015.
