[FanIn80]

Data services over 3G cellular tend to draw more power than on Wi-Fi alone. Apple's official specs show a 10% hit when using 3G vs. Wi-fi. Apple claims 10 hours of continous web usage on Wi-Fi, and 9 hours of usage on 3G with a single charge. iLounge's early tests show that these numbers seem reasonably accurate:
Our prior iPad with Wi-Fi battery tests found that Apple was generally at least a little conservative in its estimates; for instance, we put the Wi-Fi model through a web torture test with repeated 1-minute refreshes of a large, completely loaded page for 10 hours and 21 minutes on 50% brightness over 802.11n. Repeating the exact same test on the Wi-Fi + 3G model with 3G turned on and Wi-Fi turned off, the iPad achieved 8 hours and 38 minutes of continuous reloading and displaying -- 22 minutes shy of Apple’s estimate.

http://www.macrumors.com/2010/05/01/...fi-and-3g-ipad

http://www.ilounge.com/index.php/bac...view-findings/