The company says that tests which have shown a nearly two hour difference in battery life are unrealistic.
"With the Apple-designed A9 chip in your iPhone 6s or iPhone 6s Plus, you are getting the most advanced smartphone chip in the world. Every chip we ship meets Apple's highest standards for providing incredible performance and deliver great battery life, regardless of iPhone 6s capacity, color, or model.
Certain manufactured lab tests which run the processors with a continuous heavy workload until the battery depletes are not representative of real-world usage, since they spend an unrealistic amount of time at the highest CPU performance state. It's a misleading way to measure real-world battery life. Our testing and customer data show the actual battery life of the iPhone 6s and iPhone 6s Plus, even taking into account variable component differences, vary within just 2-3% of each other."
A 2-3% difference in real world tests is still more than expected; however, it's unlikely that you will notice it, especially given the new Low Power Mode in iOS 9.
If you want to check which chip you have in your device, follow these instructions.
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