From CNET: At the WWDC in San Francisco, Apple senior VP of Software Engineering Craig Federighi announced that the new iOS9 will enable improved battery on compatible devices.
By default, you should see an extra hour of battery life on iPhones running the updated operating system. There's also a new "low power" mode that Apple promises will net up to three hours of additional battery life on your iPads and iPhones.
Apple is making an effort to improve all aspects of the operating system's foundational features, designed to make the user experience faster and more productive. Meanwhile, Google is making similar adjustments to battery life and speed in the next version of its own operating system, called Android M.
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