Anyone have any hard consumption figures for 3G though? My old N8 never really seemed to show much difference between idle 2G and 3G (although I never measured it to this level) ditto for my Palm Pre and HP Pre 3. Just wanted to know what to expect really and troubleshoot if the consumption is too high. If there's a thread on this exact thing then I'll gladly post there, I just couldn't any with this exact topic in mind
vi_ is right - on top of that, I would say "dual" mode is the most battery-eating. 3G, obviously, show higher usage in tests, but it's hardly noticeable in real life, if You're on area with good coverage. BTW, it's worth to mention, that even in "high mobile Internet infrastructure" countries, there is generally better 2(.5)G coverage, than 3G, so 3G may suck more battery, just because weaker signal reception.
Mine is always on Dual, what does it really mean? I don't really think it bad on Battery, doesn't it just convert to 2G when 3G is not available?
It probes both network simultaneously - that's also why You can have both data connection with high bandwidth usage and non-interrupted calls. Generally, it is't overkill - becomes grand power sucker while traveling through regions with changing signal strength (both 2G and 3G is probed intensively), or when one (or both, obviously) range is barely reachable (low 2G or low 3G signal). As a rule of thumb, it's better to sit on 2G, and enable 3G (even in dual) when You need data connection. In some special cases, it's also good to use 3G only for calls - they're much better encrypted, as 2G was broken long time ago (yet, it's not trivial, so You can rather don't expect script-kiddies eavesdropping conversation, even on 2G). Overall, eavesdropping 3G is *much* harder, and require *very* specialist equipment, and/or cooperation from Provider, where 2G theoretically can be decrypted by tech-savvy hobbyist, with some special (still expensive, if hobbyist in question isn't tech guru and haven't DIY it) equipment.
When you are on wifi, the 3G/4G radios are in a lower power state (iirc) and even so, aren't passing any data so are using much less power than if they were kept awake and transferring data. wifi uses less power than 3G and 4G because 802.11 radios are very mature and also are dealing with connections that are feet or tens of feet versus hundreds or thousands of feet with cellular signals.
using a wifi connection doesnt actually turn off the 3g/LTE radios but keeps them at a super low power level. even if it is displaying signal bars for either or, it isn't using the radios. not sure of the technicalities, but that is just how it works. i can easily go all day on Wifi, but when i am out and about, the 3g/LTE just kills my battery.