Mobile data: how much do you need?

18 Jan 2013

Mobile data caps can be as mean as 100MB a month, so choosing a tariff can be a perilous task. David Bayon investigates the numbers

Remember when free texts and minutes were the main factors in choosing a phone contract? These days we barely even notice them, but we face a more modern dilemma when contemplating signing on the dotted line: how much mobile data is enough? It’s difficult to know the exact answer; like the free minutes that used to be wasted every month, many of us pay over the odds for data we don’t need.

Every case is different. A user with Wi-Fi at home and in the office will consume much less than a user for whom their mobile phone is the office. However, even a short commute can easily become the main data drain if you want entertaining – in October, a Citrix Bytemobile report found that video streaming accounts for 50% of the world’s mobile traffic.

It’s an eye-opening figure, so to back it up with data of our own, we posted a request on Twitter for anyone who would be willing to be our guinea pig. We asked them to install a data-monitoring app on their smartphone, and track their real-world 3G and Wi-Fi usage for seven days. By coincidence, exactly 100 people volunteered to take part in full; a further 50 estimated figures were submitted but not included in the data analysis, although we did trawl them for interesting insights.

This feature tackles the big question with a two-pronged approach. First, we choose the apps that you say commonly drink up your data allowances, and see how hungry they really are. Then we analyse the survey figures to find out how much monthly data the average user needs. The results may surprise you.

Mobile data: the media hogs

One of the questions participants were asked was which apps they used most during the test period, and it’s safe to say the same culprits cropped up repeatedly for those people with high data consumption: BBC iPlayer, Spotify and YouTube. As expected, media-streaming apps run up the big numbers.

To determine just how big, we ran a series of mobile phone tests using both the office Wi-Fi connection – which conveniently clocks in at 12Mbits/sec, the average EE says we can expect over 4G – and a 3G connection on the 3 network that we’ve measured achieving anything from 200Kbits/sec up to 1Mbit/sec.

Testing with both means that we can ascertain the data consumption of each app in its various quality settings – including those the 3G connection couldn’t handle without throttling.

An hour of Spotify radio streaming would use anything from 53MB to just over 212MB depending on connection and playback quality

First up is Spotify. The mobile app offers Normal, High and Extreme quality settings, which equate to Ogg Vorbis streams at approximately 96Kbits/sec, 160Kbits/sec and 320Kbits/sec – so you can already estimate the bare minimum amount of data they’ll use over time. We measured ten minutes of Spotify streaming at each quality setting, then repeated the tests and averaged the results to make up for any variation in tracks. The difference between Wi-Fi and 3G consumption was negligible, and we couldn’t discern any audible difference between the two through our Sennheiser headphones.

Those ten minutes of Soft Cell and Rick Astley classics consumed an average of 8.9MB at Normal quality, 21.3MB at High quality and 34.7MB at Extreme quality. Taking the lowest and highest of the figures we recorded, an hour of Spotify radio streaming would use anything from 53MB to just over 212MB depending on connection and playback quality. That’s worth bearing in mind the next time you set off for work relying on a Toto album to prepare you for the day ahead.

However, it’s nothing compared with the damage done by streaming video. To test BBC iPlayer, we used an hour-long special of The Thick of It, which is listed as 637MB when downloaded at High quality over Wi-Fi. That’s fine for download – the file size is labelled clearly enough that you know exactly what you’re getting – but what about when streaming the same episode?

Over 3G on an iPhone 5, with the picture sharp except for a few momentary lapses into pixellation, ten minutes of viewing consumed 32.6MB, so for the full hour you’d be looking at just short of 200MB. On Wi-Fi, with no connection speed constraints on picture quality, the same ten minutes consumed 75.5MB, for an hourly total of around 450MB. For many people, that would be a month’s data allowance gobbled up by a single TV episode.

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Analysis