Which = 3g or Wifi will drain the battery faster?

[bcserl]

I am having a disagreement with my buddy. Will leaving your Wifi on full time at home for receiving data drain your battery faster than using 3g?

 

[aminaked]

There's no easy answer because it depends on how good the 3G and wifi signals are and how you use your phone, but in general you want to leave wifi on because it uses less power. The 3G signals have to travel a lot farther than the wifi signals so it makes sense intuitively. You can find lotsa info on this by doing a google search.

 

[furbearingmammal]

WiFi uses a lot less battery than the 3G with two caveats -- if you do NOT have a WiFi connection so the WiFi system is constantly scanning you will suck battery life through a hose, or if you're rooted and using WiFi tethering it will suck your battery faster than almost anything else.

Just a quick thought exercise here for you to consider. Your nearest access point is maybe 200 feet away. Your nearest cell tower can be several miles away. Which one is going to take more juice to carry the signal?

 

[kodiak799]

I think when idle (but not searching for a signal) Wifi uses a lot more battery than 3G, maybe 2-3X. Wifi sucks more juice just sitting there, but will use less when transferring data since the CPU is actively engaged for a shorter time period, but I wouldn't think it noticeable for texts and emails (without attachments) because those are pretty small files that move quickly enough over 3G.

Depends on how much emails and texts you get if it's better to always leave Wifi on. I think for widgets and other stuff that update, you'll get marginally better battery life turning Wifi off when not actively using it.

with minimal other use and the screen always on min brightness, I get maybe 15 hours of battery life and wifi uses 5% - so @45 minutes? Pretty marginal savings I'd say.

 

[aminaked]

if you do NOT have a WiFi connection so the WiFi system is constantly scanning

I leave my wifi setting on all the time. I have set it to NOT notify me of open networks. Are you saying that if I check the box to be notified, then the wifi will be doing much more work than if I just have it connect to some remembered networks? To me, it seems like the wifi would be scanning the same amount either way.

 

[dolpns13]

so when your wifi is on and connected, it automatically turns off your 3g?

 

[aminaked]

Yes, it turns off your 3G.

I don't think scanning takes much juice. If it's just receiving and not sending, it should have a minimal effect on battery.

I say if you connect to wifi at least once/day then just leave the wifi setting on and use wifi whenever you can. Also, by default wifi is set to shut off when the screen is off. There is a setting to change this but I don't think it's a good idea to leave it always on for most people.

 

[aaf709]

Another thing to consider; when running right, WiFi runs much faster than 3G. This means you'll be spending less time downloading data.

 

[kodiak799]

I leave my wifi setting on all the time. I have set it to NOT notify me of open networks.

That's interesting. I have the same setting (which I think is the default?). But I've never noticed a drain when I accidentally leave wifi on and go out and about.

I actually use Locale to turn off Wifi when I go out of range of my home Wifi. Different profiles for work, parents house, etc.. to connect to their wifi when in range....location based on GPS/towers so it doesn't scan unless my location says I should be in range.

 

[furbearingmammal]

As a general note, most custom ROMs have active scanning periods for the WiFi stretched further apart in a specific attempt to save battery life. If you're in an area with WiFi connectivity that's good, leave it on all the time. If you're in an area with poor or no connectivity, just leave it off. 3G usage depends on how many programs you have active that use data, and if you have Sync turned on you may have programs phoning home constantly. 3G is much more powerful a signal (again, look at the distances you have to cover), and sending always takes more than receiving, so on the average you'll use far less with a solid WiFi connection for web browsing and most data-intensive tasks.

Merely turning off the notification should have no impact on your scanning, but that's my opinion based on empirical data. I believe it's still looking; it's just not telling you what it's finding.

 

[aminaked]

I like the idea of using locale to manage wifi BUT I think in the end if it uses GPS it will end up using more battery power than just leaving wifi on. If you're already using locale for something else, adding wifi would probably be a good idea, but I wouldn't install it just for wifi.

Merely turning off the notification should have no impact on your scanning, but that's my opinion based on empirical data.

OK, that's what I was thinking too.

People should just try it both ways. I had wifi off on my phone for about a month (because of a problem in 2.01 which I won't get into here). When I finally started using wifi again after the 2.1 update, my battery life got noticeably better. The OS update could have something to do with it, but I think it was the wifi.

 

[kodiak799]

As a general note, most custom ROMs have active scanning periods for the WiFi stretched further apart in a specific attempt to save battery life.

Now there's an idea...Looks like BB0.4 is set to scan every 60 seconds....Would be nice to be able to have a profile where it would change the setting to scan every 3 minutes (or 10 minutes, not sure how it works) if I'm in the house where I have a very solid wifi connection. Seems like that could reduce idle wifi usage by a few multiples.

 

[kodiak799]

I like the idea of using locale to manage wifi BUT I think in the end if it uses GPS it will end up using more battery power than just leaving wifi on.

Nope. I have wifi locations trained (in Locale) and my phone uses both wifi and GPS for location. Been home for about 6 hours and it's telling me it has not used GPS. I rarely seeing GPS draining battery anyway.

 

[aminaked]

Nah, not for me. I like how it works stock. I have wifi right away every time. If it only scanned every 60 seconds, wouldn't that mean that 3G might get going for a minute until wifi got set up? That would end up using more power.

I say leave it on and don't worry about it.

 

[kodiak799]

Nah, not for me. I like how it works stock. I have wifi right away every time. If it only scanned every 60 seconds, wouldn't that mean that 3G might get going for a minute until wifi got set up? That would end up using more power.

I say leave it on and don't worry about it.

To each their own....The min radius for locale is 100 meters, I think, so it's generally looking for my wifi before I even walk thru the door. Also, I believe when wifi is turned on or off it automatically triggers a scan.