Apple Thoughts: Want Faster iPhone 4 Charging? Use AC Rather Than USB

"This whole charging / not charging issue with the iPad and iPhone is pretty confusing. At least with the iPad, if it's not plugged into an outlet or a USB port that's delivering enough juice, you get the whole "not charging" message near the battery indicator ... yet, it does charge, but slowly."

While USB charging does work for the iPhone 4, it will take longer via USB than it will by simply plugging it in to an outlet. In WhenWillApple? testing ( link ), a completely dead iPhone 4 took 130 minutes to fully charge on AC, and 160 minutes to fully charge via USB on a late-model MacBookPro. From dead to able-to-power-on took 3:11 (m:s) on AC, and 4:49 (m:s) via USB. While the idea of slower charging via USB sounds like a case for using the AC adapter more often, I find that keeping my iPhone 4 connected via USB when I'm at my desk works well enough, and I'm less apt to walk off without my phone, when it's sitting right under my nose. But for the most charge in the shortest time: plug it in!