MacRumors has put the Low Power mode through its paces and found processor speeds are throttled by up to 40 per cent when the battery-extending feature is in operation.
Apple says the tool, which comes into effect when battery life drops below 20 per cent, saves power by shutting down some features and pulling back on others.
Mail will have to be checked manually, background app refresh is turned off, downloads are disabled, network speeds are slowed and motion effects and brightness are dialed down.
However, the explanation of the feature on Apple’s website makes no mention of such a dramatic downturn in performance.
The tests were conducted using the benchmarking tool Geekbench 3 on the iPhone 6 Plus and iPhone 5S. Both the single-core and multi-core processor tests showed a significant throttling of performance.
The site wrote: “Without Low Power mode activated, an iPhone 6 Plus scored 1606 on the single-core processor test and 2891 on the multi-core processor test. When Low Power mode was turned on, the same iPhone 6 Plus scored 1019 on the single-core test and 1751 on the multi-core test, suggesting there's a significant performance reduction when Low Power mode is enabled to save as much battery as possible.”
The performance throttling is unlikely to bother iPhone users who would welcome their phone staying alive by any means necessary. However, it would be nice to see Apple address it in some form.
iOS 9 is already scheduled to give iPhone users an extra hour of battery life thanks to improved efficiency, making it easier to survive a long day and beyond.