My understanding is that the iPhone makes the wifi go to sleep when not connected to a power source and uses 3G to save battery. That was the standard behaviour until recently. Now I have changed mobile provider to Three UK, and I have noticed that wifi stays always on even when locked and not charging. Is my iPhone wasting battery now? Why the change? I recently installed an app from three called "Three Intouch" which has an option that says "keep wi-fi connection alive" that came enabled by default. I disabled it and even removed the app, but wi-fi still stays on while sleeping. Do you think that it was caused by this app, or is it just the three network that maybe uses more battery than wifi now and the iPhone decides that it's more efficient? When I try to google this problem I get thousands of threads of people complaining about the opposite problem (wi-fi being disabled when on sleep), but I haven't seen anybody with this particular problem (Wifi staying ON).