[Windows Phone 7 General] andycted:
While the theory behind that is correct, and thanks for the tips, there are a few points which aren't 100% correct I think. I've done extensive battery tests with smartphones that allowed it (WinMo and Android) and I think that the most gain from turning 3G off is when you have a non-optimal reception, as it eats more battery than just gsm only, when connecting/dropping/reconnecting/searching.

WiFi in comparison (always depending on signal quality though) eats more battery while transferring data, per second, but can also transfer more data in that second. On idle, WiFi looks to be less consuming.

But both won't be a huge battery drain on idle. That said, when I'm very very low on battery, I do turn off 3G too.

If you leave 3G on, but don't use it (with the battery saver or settings, and leave the phone idle), depending on your signal quality, the drain won't be major.

The push vs interval email check settings are a bit different in every platform. It all comes down on how good the 'push' implementation is and -again- your signal quality of course. This because -while interval check just opens the connection once every 15/30/60 minutes and then downloads emails if available- the push setting tries to keep the connection to the server pretty much alive, or rather it tries to keep the channel open so that the hotmail server can push the emails when they arrive.

This however is implemented differently on every platform. In google gmail in android it is pure perfection. The connection uses close to zero energy to stay alive and has a drop-retry pattern which is very optimized. You can try other email programs, even for gmail, on the same phone and it will come out using a lot more battery for push. I think that developing the server, push system and the client entitles them to optimizing it hehe.

Anyway, on WP7 there are no available battery drain monitors (you know the ones that log or tell you in real time the mA or mAh used) so one can't be sure. Being a very new operating system, I would tend to think push email drains a bit more than what android, which has been optimized for years, does with gmail.

Regardless of this, the drain of push email vs interval check (pull), occurs mostly if you receive emails very frequently. This because being contacted 20 times in 15 minutes to discharge an email from the server, possibly while not always in optimal signal strength, is more heavy than discharging all the 20 emails at once after 15 minutes.

It seems to me that when you manually or automatically lose the data connection, and then regain it, wp7 fetches automatically emails if the interval of time for the check has passed or, of course, if push email is on. This is quite better than what I experienced on android 2.1 where reobtaining the connection didn't always trigger an email check (withouth push). So I tend to leave push off and keep an interval around 30 minutes on wp7, but of course that depends on anyone's needs.

Lastly, I'm not sure if the push email energy use is affected by the entire push framework of wp7. Since pretty much a lot of the desktop relies on push (live tiles, notifications, etc), maybe the system is already busy mantaining the channel open with a single server, or mantaining multiple push channels open don't affect battery life, and thus push email doesn't really affect the battery because of this. Still, usually on smartphones, when push fails because the connection isn't reliable it falls back in a frequent-pull which can eat your battery pretty fast...

All in all, tips are good, but a second battery is best :)