A recent tweet from OnLeaks cites a reliable source suggesting that the battery in the new iPhone being released this fall will likely see a modest increase from the battery in the iPhone 6s, jumping to 1960 mAh from the 1715 mAh capacity of the current model.
Pretty reliable (not 100% but almost…) source told me #iPhone7 battery = 1960mAh (#iPhone6s = 1715mAh) — OnLeaks (@OnLeaks) July 13, 2016
These numbers presumably represent the battery capacity for the standard 4.7” iPhone model, rather than the larger Plus/Pro models that have been rumored. Last year’s iPhone 6s actually saw a slight decrease in raw battery capacity from the 2014 iPhone 6 model, which came in at 1810 mAh, although both the 2014 and 2015 iPhone models achieved roughly the same actual battery life despite the capacity differences. It’s unclear whether any increased capacity for the iPhone 7 would be intended to mean longer battery life, or if it would simply be required to supply the additional power for new components.