Documentation says that the total amps supplied is 3.1 with either port being able supply 3.1A when used alone.
Customer Image Gallery for PowerGen Dual USB 3.1A 15w Travel Wall Charger with Swivel plug for Apple iPad 2, New iPad 3, iPhone 5 4s 4 3 3Gs, HTC Samsung Motorola Android Phones (USB Cable NOT included) - white
one port is configured for Apple products while the other is for standard USB configurations.
MP3 players, ipods, iphone 4s, iphone 4s, iphone 3G, Apple iPad, Mobile phones, PDA, GPS, MP4, Portable wifi, Amazon Kindle fire / DX and other kindles.
USB Port 1 (labeled as A port, Designed for Apple products) Compatibility
iPad @ 2 Ampere Max.
iPhone / iPod Touch @ 1 Ampere Max.
Others phones / GPS / Tablet etc. @ 0.5 to 3.1A Ampere Max. (May not support charging / or slow charging with some devices)
USB Port 2 (labeled as NA Port, designed for non apple products) Compatibility
iPad @ NOT Compatible
iPhone / iPod Touch @ 0.5 Ampere Max.
Others phones / GPS / Tablet etc. @ 1 to 3.1A Ampere Max.
NOTE 1:Currently known support tablets: Samsung Galaxy Tab Series, Amazon Kindle Fire & all other Kindles,Nook Color, HTC Flyer, Huawei Tablets.
NOTE 2: NOT compatible with HP TouchPad, Asus transformer, Motorola Xoom or Blackberry Playbook.