To replace the battery in your iPhone, visit an Apple-authorized service location or any Apple Store. Replacement batteries for the iPhone should only be installed by professionals approved by Apple.
The cost of replacing your iPhone battery can vary based on your phone's warranty program. According to Apple, repairs can take up to five business days. In some cases, Apple may offer a loaner iPhone to you while your phone is serviced. If you purchased AppleCare+ with your iPhone and the battery retains lower than 80 percent of its original capacity, it automatically qualifies to receive a free battery replacement as of 2015. Prior to receiving a battery replacement, remember to backup the data on your iPhone.