This must be phone dependent. I have my Blackberry 8900 on wifi all day and it maybe goes down by 20% in 24 hours. I'm currently in Mexico so I leave the GSM radio off and it seems that the battery lasts longer this way.
I there a way to turn GSM off on Android/CM? That would be great for situations where I do actually have wifi coverage.
I believe when Wi-Fi is running that GSM data is automatically disabled. When you turn off Wi-Fi you'll see it takes a few seconds to re-establish the GSM data connection. I know you can turn off the roaming data. You may need a rooted Android ROM to completely disable GSM. Some people on XDA Developers have talked about that.
On the Nexus One you can enter a test settings screen where I'm pretty sure you can turn off the GSM radio completely.
I use the "Secret Settings" app, which gives me access to all the test screens without having to remember the test codes. I can switch all that stuff in there, IIRC.
> I believe when Wi-Fi is running that GSM data is automatically disabled.
Right; I use SIP, so I want GSM disabled entirely, not just for data. Will take a look.