Cellular iPads consume 3x the mobile data as smartphones

Since the iPad(s aapl) arrived more than three years ago, Wi-Fi-only versions of the tablet have been far more popular than cellular-capable models. But things may finally be swinging in a different direction. Data use coming from iPads has grown four times in just the last six months, according to data gleaned from mobile network operators by U.K.-based analytics software company Actix. And for the first time, there are two different iPad models among the top 10 most data-hungry devices, which has always only had smartphones on it.

It’s not the latest 4G-capable iPad that’s eating up all this data, though, it’s older 3G models: the iPad 2 and iPad 3 are now No. 6 and No. 7, respectively, on this list, says Actix; the rest are smartphones. There has never been a tablet, much less two, on the list of the most mobile data-hungry devices before. Actix gets this information from software it runs on the networks of eight carriers: one European, one Middle Eastern, two American and four based in the Asia Pacific region.

Why is this number suddenly growing just since the end of 2012, when the iPad 2 has been around since early 2011 and the iPad 3 since early 2012? Mobile broadband subscriptions grew 45 percent faster in the first three months of 2013 than a year earlier, according to a recently published study by Ericsson.

It could be customers are taking advantage of more flexible mobile plans, like the shared data plans AT&T(s s) and Verizon(s vz)(s vod) now offer. Rather than buy a separate subscription for their tablets, customers can attach to them to their smartphone plans, encouraging customers to connect their iPads to cellular networks instead of just relying on Wi-Fi connectivity.

But it could also be a sign of the continued popularity of Apple’s older model iPads. Though cellular models are more expensive, older models get sold at a discount. When the fourth-generation iPad debuted in late 2012, Apple started selling the 16GB iPad 2 + Cellular for $529 (down from the price of $629). The iPad 3, however, was discontinued.

Another thing propelling iPads up the list, Actix says, is that Apple’s tablets are consuming three times more mobile data than the average smartphone.

If this trend holds out, it could mean a windfall for carriers who can sell bigger buckets of data to tablet users, but the opposite could be true for consumers, who will end up footing those bills.