AnandTech dug into the FCC filings for the new iPhones to reveal that the iPhone 5s battery offers approximately 10 percent more capacity than its predecessor, while the 5c battery offers a more modest 5 percent gain. That’s a different size battery (5.96Wh vs 5.92Wh) than we’d seen in supposed 5s prototypes … 

Actual battery-life for the iPhone 5s will be interesting to see. The beefier A7 CPU will consume more power, while the M7 coprocessor that handles some of the background tasks should reduce battery consumption. How the two balance out is not yet known, though Apple did promise better battery-life than the iPhone 5.