I can use simple math to get the charge rate of the panel by comparing its charge time to the wall chargers charge time and mA output rating.
~ Normal charge durations ~
From a completely dead battery to 100% takes about 4 hours via USB charging. Using the wall adapter takes roughly 3 hours. From the 20% warning alert to 100% takes about 2 hours via USB. The battery will "fast charge" to 80% pretty quick and then "trickle charge" slowly the remaining 20%.
from this link on apples site:
https://discussions.apple.com/thread/3453933