On Friday, Apple announced that it had discovered that "a very small percentage" of first-run iPhone 5 units -- those sold between September of 2012 and January of 2013 --
have a defect that results in unusually short battery life, and have
instituted a program to replace the battery. Users will need to bring the units to an Apple Authorized Service Provider or retail Apple Store; however, customers should be aware that Apple will send the unit off to a facility to be inspected.
While "loaner" iPhones may or may not be available (there is no mention of it on the web page), a serial number from the iPhone in question is required to process any service requests. If the unit is found to have the defect, Apple will replace the battery at no charge, even if the iPhone is outside of warranty (up until March 1, 2015). A page has been set up on the company's website to help determine if the unit falls within the range required to qualify for the program, which is limited to the US and China for now, but will later be expanded to other countries.
In addition to having experienced the issue of unusual battery shortness, the iPhone 5 must still be in working condition in order to be eligible for the battery exchange. Other damage that could affect the part swap would have to be repaired first at normal rates.