With all the posts going around regarding data drain on WP7 devices I decided to do some simple testing on my device to see if any of the claims regarding Microsoft Feedback or Phone Update using excessive data were true. Needless to say, after eight days I am probably more confused now than I was when I started.

For starters, I am on a grandfathered AT&T Unlimited Data Plan, so data use is more a curiosity for me than anything. But I am interested in helping the poor souls with 200MB plans. I was never a really big data user (iPhoner’s should thank me for giving them my excess allotment) but in the first two months (first month adjusted for a full cycle) with my Surround I was averaging 1.7GB/month. After a failed data experiment with an AT&T MicroCell (data is actually worse than 3G) and discovering that battery drain on my WP7 device was minimal with WiFi turned on, I decided to go WiFi 24/7 a day or two after my month/cycle (26th) started. And aside from running errands and a couple times when I was away from the house for a good part of the day, WiFi has been available constantly. 3G in the house was averaging 1.3-1.7 Mbps while WiFi is typically 6.8-8.0 Mbps, so I rationalized that any extra battery usage from WiFi would be made up with quicker download speeds. And of course, there are some things you just can’t view or listen to over the spotty 3G connection.

The excess 3G data usage some are reporting is important to me because I equate data uploading/downloading to battery drain and with my meager 1300 mAh battery, I need every drop I can get. The chart below describes where I was on each day, starting on 1/11/11 through this morning. I started by turning Feedback off (Settings>Feedback) and then followed that up with turning the Phone Update/Cellular option off as well (Settings>Phone Update). By 1/14, I though I was on to something and was going to report a “breakthrough”, but I forgot to check my data usage the night of the 15th and when I checked the next morning I discovered that I had consumed 83MB of 3G data. WTF. Now, I was away from the house on the 15th, out of WiFi range, for several hours watching the Steelers/Ravens game. But the only thing unusual I did with my phone was use Bing/Wikipedia to check the size of an NFL Officials Crew (the answer is 7). Can’t imaging that amounted to 50MB+ of additional usage. On the 16th, while within WiFi range, I downloaded a new app, MiraTV and played around with it for about 45 minutes, looking for working TV feeds. I also listened to some streaming Zune music and download 9 songs to my device. I was really surprised the next morning when I discovered that I had consumed 197MB of 3G data. After playing with MiraTV a bit yesterday, checking feeds that were closed the night before, and doing all the normal tinkering I do with my device all day, this morning I was perplexed to see that only 3MB of data had been added to my 3G total.


I know that when your WP7 device is on charge (AC or USB), WiFi stays on constant and when off charge, WiFi will go to sleep after 45 seconds of screen off (yes, I also tested this). So there are times where 3G will take over to push/sync email, push Live Tile updates, etc., but most of the heavy lifting is done when the screen is turned on and WiFi “is” connected. Additionally, my phone is on charge every night for at least 7 hours, plus it’s usually plugged into a portable backup battery charger for my late day power boost 1-2 hours each day, and/or connected to my PC syncing Zune. So almost half the day, I am WiFi on “constant” and “on demand” the rest of the day. Now, there have been times that my BrightHouse cable connection will simply turn off, usually not more than 5 minutes, and then restart on it’s own. But that’s rare and I would have a hard time pinning that to either of the data usage boosts described above.

So what is using 3G data, sometimes at alarmingly high rates. Third party apps can’t run in the background, but maybe some are not optimized to use WiFi when available. Not sure how that works. It could be the Microsoft built-in services, but I somehow find it difficult to believe that this is equating to MB’s worth of data. Maybe a few KB’s, but MB’s? Or, could it be the OEM or Cellular provider doing things that we don’t know about. Not sure how much access they have to my device. It’s been reported that AT&T records their data usage in lumps, which could explain the jumps above, but it still does not explain how I consumed that much 3G data, with WiFi constantly turned on and within range about 80-90% of every day on average. The only way to truly test all of this is with a fresh, app free device, with a Windows Live ID setup and basically nothing else. But who would want to walk around with that for a week or two. Not me. Using today’s average, I may hit around 1.1GB for the month which is a lot more than I expected, running WiFi all the time. Now that we are into the third month of WP7, how has your experience been? Are those on the 200MB plans still keeping the data numbers down? Anything unusual to report?


  1. what are you using to get these data numbers? texting *data# from the phone or going to wireless.att.com and logging into your account?

  2. Getting the numbers from the AT&T app on the phone. Figured if I checked around the same time every day the info would be sort of consistent.

  3. try using *data# and see if that gives you a number different from the app. i just checked my account again and with wifi on all the time i used 124.4 MB last full billing cycle. and i have updates and reporting turned ON, very interesting to see that high of a jump when you didnt think you used the phone much, makes me think the app has a couple day delay or something.

  4. From my experience over the past 3 years of watching data usage, the AT&T data billing does not update with super accurate time stamps. I have observed it to be delayed often and bunched up.

    The AT&T data usage log is good for general longer term usage amounts (week kind of granularity), but I have observed it to be not at all accurate for a day by day monitoring.

  5. What about contacts? How much data is being pulled from Facebook in “what’s new”? I also wonder how much data is used for xbox live (syncing) and zune (all those background pictures).

  6. On Paul Thurrott’s Windows Phone Secrets website (windowsphonesecrets.com), this issue has been discussed several times over the past few months. I’ve been running a Windows Phone since the day after launch with Feedback on, Phone Updates on, Facebook enabled, Gmail push, Hotmail push, and a Zune Pass. What I’ve found is that which has been reported by a few other users, the phone will begin downloads of large apps (over 20 MB) only when connected to a PC or Wi-Fi. However, if you begin such a download then manage to disconnect from Wi-Fi (by letting the screen lock and 45 seconds elapse, or by actually moving out of Wi-Fi range) the phone will continue downloading the app. With some of the Xbox Live games, this could easily account for 100+ MB. I suggest doing a few tests downloading large apps and then disconnecting the Wi-Fi to see it for yourself. If you hold-tap on an item in the download “queue” you can pause it for later; however, this is only a workaround for an obvious bug in Windows Phone 7’s Marketplace.

  7. Also, for what it’s worth, I have not personally experienced any data usage I cannot account for. But I have noticed the Marketplace behavior I just described above and I believe that may be the cause behind most of these excessive data usage complaints. Others may simply be users not accustomed to having a smartphone and how easily one can transfer hundreds of MBs if they use it all day long for streaming pictures, music, and/or videos.

  8. Just compared my account on-line with the info on the phone app and everything is identical; data, messaging, anytime minutes and mobile-to-mobile. Where do I text *data# to. Can’t find anything on the AT&T site.

    Looking at my billing details, data almost always gets posted between 12-1am or 12-1pm, with very few exceptions. Last three entries are 3154K on 1/17 at 12:07am, 109450K on 1/16 at 12:07am and 92171 on 1/15 at 12;23pm, Guess there is a delay in getting it posted to the cumulative total.

  9. @RC Electron: True, and obvious from my last post. But if I am on WiFi almost all the time and for the past three weeks have not really used the phone much (no streaming, no video, etc.) when away from my WiFi signal, why 800MB+ for the month so far?

    @yss: Yes, I do sync 3 email accounts, so maybe 60-90 messages per day, but that’s only data. Photos or other graphics don’t download till I am reading the message, presumably using WiFi. I think Facebook only updates when you open the people hub, again while WiFi is on. And for XBox and Zune, again my screen is on so WiFi is on and working.

    @Mark Jonson: Understood. I only have a few XBox games installed and have not purchased any new in the past month. I get Marketplace app updates almost every day, but for the most part I am alway within my WiFi signal. Will need to check how my Wifi signal is around the fringes to see if that can explain the extra data usage. BTW, WiFi will not turn off after 45 seconds, even with screen off if it is “in use” as with streaming music or even if you get new mail after turning off the screen and before the 45 second timeout. Timeout will restart after a disconnect from the data source. Tested this multiple times too make certain I got that part right.

    Not sitting around recording everything I do with my phone as I really don’t care how much data I use. More a curiousity than anything. And no doubt that AT&T will again adjust their tiering with 4G coming (see Sprint) so I do want to know if I can survive on a lesser data plan. Just planning for the future.

  10. you just punch in *data# into your phone dialer and hit send and it will request a free text message from the network, you dont actually text that to a number, sorry for the confusion

  11. So, if I have my data turned on and there is a wifi connection; will the wifi connection overtake the data while I happen to do anything involving data usage? I’d like some clarification because I don’t like turning my data on and off when needed.

  12. hypothetically you can leave your data usage on and as long as your phone says “connected” when you look at your wifi page under settings it wont use any cellular data, you shouldnt need to turn cellular data on and off, the phone should do it for you, but thats kind of the point of this article is that the phones seem to be transferring data over cellular even though it is connected to wifi. so i dont think there is any “clarifying” right now.

  13. I believe, theoretically, that’s what is supposed to happen. If WiFi is on, and you have an active connection, the default for data transfer will be via WiFi. But if your WiFi connection drops out, like if you walk out of range, during a data transfer or an app download/update for example, the connection will revert to 3G, if available, and proceed from there. Also, when your screen is off, your WiFi onnection will become idle after about 45 seconds of no access (like not streaming music or downloading an app) to save battery, so any periodic email sync or push notifications will occur over 3G, again if enabled. As soon as you turn your device on, WiFi will instantly become available again.

    With that said, I have been experiencing more 3G data transfer than expected with my WiFi enabled and active all the time. I just changed the channel on my WiFi router and that seems to have improved the signal somewhat so I will see if that makes a difference.

  14. Oh cool, thanks for explaining that to me. I only turn data off because I have a 200 MB plan and I don’t use “3G” unless i’m driving and I need to get somewhere– not that I need the GPS it’s just fun to use. There is wifi everywhere I go except for work which is a secured network that requires mac address to have full access to the wifi and that’s a bummer, logging on every time I get off sleep mode sucksk.

  15. Just to clarify, you don’t need to log back in every time your phone wakes up. It will automatically connect with your last wireless network, or one that have previously connected to. If that’s a work restriction thing, you can get your MAC address by looking it up on your home wireless router. Or get them to turn off MAC filtering for 5 minutes, identify and record your address, and then turn it back on.
    With your 200MB plan, I would test it out for a couple days, checking data usage on your phone every day just to be sure you are not running up your data numbers.

  16. I use my phone for internet browsing mostly when away from my home wifi. Also, a bit of facebook status reading, and I sync Hotmail and my work email account. I just checked my data usage at Telus.ca and for the last 30 days I’ve used approx. 295MB. No problems at my end. Everything is accounted for.

  17. Thanks everyone for the feedback. Only 12MB yesterday (847/m) so maybe I am getting a handle on this. But I never left the house so should have been in range all day. If I was a betting man, and I do use MyBookie every day, I would guess that one or more 3party apps are NOT optimized to access WiFi. Again, not sure if this is controlled by app code or the OS, but as several built-in services have options for 3G/WiFi, I suspect the former. Not ready to spend the time testing each app I use regularly. If I was independently wealthy I could get another device/SIM and load one app at a time till I found the little bugger, but that’s not happening any time soon. Boy, do I miss SPB Wireless Monitor at times like this. With that app enabled, I would have my answer in 24 hours. Oh well.

  18. I knew about the automatic WiFi connection. I’ll try finding my Mac address at home since there is no way my workplace would turn off Mac filtering for one individual(it’s a university).

  19. Understood. Your WiFi router should show you which devices are connected, by their MAC address. Some will identify devices by physical name also, but my Linksys only shows my Surround by MAC. If you have more than one device connected just make sure you identify which is your phone. Looks like this: 00:00:0x:xx:00:00, with a combination of numbers and lower case letters.

  20. This WP7 data leak caused AT&T to charge me $950 for international roaming charges while on a cruise ship in December. Normally, while cruising, I’d accumulate around $20 worth of charges for a one week cruise. Admins, if interested in the details, feel free to email me for more info.

  21. Yowza. That’s a serious problem. Hopefully AT&T is working with you, but obviously addresses the need to make this go away. Reports from MS state that “a third party solution commonly accessed from Windows Phone” is the root cause. Not sure what that means exactly or when the problem will go away. But if they just slip the solution in we may never know what the initial cause was, or if there are others. Used 30MB of 3G yesterday while on WiFi, compared to 12MB the day before, but I did update a could apps while out of range so it might have been me. Still curious though.

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