USB - 230v Socket Outlets
Most 230 volt socket outlets that include a USB outlet, give out 5 volt and 2.1 amp
iPhone chargers give out 5W to charge this equates to 1 Amp
iPad's chargers give out 12W to charge this equates to 2.4 Amp
Links
http://www.igeeksblog.com/ipad-charging-slowly-how-to-charge-ipad-faster/
http://www.supercircuits.com/resources/tools/volts-watts-amps-converter