This post was created to help maximize the potential of your iPhone's battery. If you read something you disagree with, disagree. If you wish to have something added to this original post, please comment and state what information should be added. I take no responsibility if you damage your iPhone by doing something mentioned in this thread. (Abby Technology LImited, Auckland, New Zealand. +64212640000)
Rated Battery Life
3Gs vs. 3G Battery Test: 3GS up to 45% better than 3G, despite Apple's claim
iPhone 4
Talk Time - 3G 7 hours / EDGE 14 hours
Web Browsing - 3G 6 hours / WiFi 10 hours
Video Playback - 10 hours
Audio Playback - 40 hours
Standby Time - 300 hours
iPhone 3GS
Talk Time - 3G 5 hours / EDGE 12 hours
Web Browsing - 3G 5 hours / WiFi 9 hours
Video Playback - 10 hours
Audio Playback - 30 hours
Standby Time - 300 hours
iPhone 3G
Talk Time - 3G 5 hours / EDGE 10 hours
Web Browsing - 3G 5 hours / WiFi 6 hours
Video Playback - 7 hours
Audio Playback - 24 hours
Standby Time - 300 hours
iPhone
Talk Time - EDGE 8 hours
Web Browsing - WiFi 6 hours
Video Playback - 7 hours
Audio Playback - 24 hours
Standby Time - 250 hours
Power Saving Tips
#1 - Always go to the home screen before putting your iPhone in standby mode. If you are running an App and hit the Sleep/Wake button to turn the screen off, the application will still be running in the background and can severely drain your battery.
#2 - Disable 3G on long calls (Ex: business calls, calling your cable company, or calling ATT Customer Service ). Call quality on EDGE is quite good compared to 3G.
#3 - If your apartment / house has a weak 3G signal, definitely turn off 3G until you leave your home. My apartment has a very weak 3G signal. The phone switches networks constantly if I have 3G enabled, which murders my battery. I use EDGE while I'm at home w/ WiFi for data. When I leave my home, I turn on 3G.
#4 - Enable WiFi in your apartment / house when WiFi is available. Use WiFi instead of 3G or EDGE for web browsing. WiFi is (with a strong signal) faster than 3G or EDGE. WiFi also uses significantly less battery power than any cellular network.
#5 - If you only use WiFi hotspots, keep WiFi disabled. Enable WiFi when you enter a hotspot.
#6 - If you don't need GPS, disable Location Services. When Location Services is enabled, your GPS antenna is activated. The GPS antenna will continue to drain battery life, even if you aren't using an application that needs Location Services.
#7 - Disable Push notifications, unless needed. It is estimated that your battery life will decrease by 20% (about an hour) with Push enabled. Increasing your fetch interval to an hour or above will also increase battery life.
#8 - Disable Bluetooth if you have no Bluetooth devices (duh). If you're like me and use Bluetooth in your car, I would just leave Bluetooth ON for convenience so you don't have to enable Bluetooth every time you go for a drive. More trouble than it's worth.
#9 - Using App Store programs may HEAVILY decrease battery life. Games (especially 3D) are notorious for killing your battery. Don't be surprised to get 2 - 3 hour usage statistics while gaming.
#10 - Enable Auto Brightness
#11 - If you have no service at all, use Airplane mode. With no service, your phone will constantly look for a signal, which kills your battery very quickly. Airplane Mode will let you use your phone, but you won't be able to dial or receive calls.
#12 - Make sure Auto-Lock is set @ 1 minute.
#13 - If you mainly use your phone for talking / texting / email / gaming, using EDGE will offer a similar experience, but your battery life will increase significantly.
