When Google Glass opens up to the public, it's going to be pricey in more ways than one. Naturally, there's the upfront cost of buying the thing, which likely won't be subsidized by wireless carriers the way cellphones are now. But a Glass-enabled population will also impose other costs, too. Consumers will need to start buying larger and faster data plans just to feed these devices. And by doing so, they'll be putting enormous new burdens on the country's Internet infrastructure.

To talk about how this might happen, we have to dig a little into how Glass connects to the Internet. The device doesn't have a cellular radio of its own. Instead, the way it links to the Web (when it's not on Wi-Fi) is through your cellphone or tablet's data plan. You might know this as tethering — using your data-enabled device as a mobile hotspot.

Carriers have all sorts of rules about tethering, and sorting through them can be like feeling your way down a dark alley. Verizon used to charge $20 a month for tethering before the FCC ruled it had to allow tethering for free. Now, any data you use comes out of your cellular plan's overall data allowance. AT&T gives you a separate pool of data for tethering plans, but charges up to $50 a month for the right, much as Verizon once did.

The Internet went through a similar transition a decade ago. Phone companies accustomed to charging for every new Internet connection in a household were taken aback when consumers started going out and buying these cheap things called Wi-Fi routers. Suddenly, one link to the Web could be split among two desktops and a laptop.

Today, most residential broadband providers will give you a wireless router — for free.

You can see the analogy. Where Wi-Fi made it possible to "tether" multiple PCs to the same Internet account, cellphone carriers will soon wind up being mainly Internet providers selling tetherable mobile broadband.

How much data will we really need?

So what would a world of widespread tethering look like? Unfortunately, there's surprisingly little data on how much tethering goes on today. Nobody I spoke to has studied this stuff. Not Akamai, the company that monitors Web traffic around the world. Not Cisco, which publishes an annual study of global broadband trends. Not the Pew Research Center, which maintains a robust Internet-related survey project.

But we can make a few back-of-the-envelope calculations. Ten percent of Americans say they'd try Google Glass if they could. That's a lot. A surge of interest for Glass — or for other wearable tech, like Apple's rumored iWatch — would transform tethering forever. Tethering would go from being a nice-to-have feature that's occasionally useful when you're on the road to something that's absolutely necessary for your new toy to function as advertised. And, assuming the FCC didn't require all wireless carriers to make tethering free, it'd be a huge source of potential revenue for companies like AT&T.

Imagine if 35 million Americans got Glass tomorrow. Almost overnight, it'd place major burdens on the country's telecom infrastructure. This is something we've seen before, said Gregory Rosston, a Stanford researcher and the former deputy chief economist of the FCC.

"The iPhone was a game changer in terms of how much data people used," said Rosston. "That caused two things: The carriers built out much more capacity . . . and they pushed people to pay for data. I think if Google Glass takes off, two similar things will happen."

A massive uptick in the demand for wireless data will, in turn, add more congestion to the airwaves carrying those signals. To head off that possibility, the FCC next year aims to buy up valuable wireless spectrum from television broadcasters and sell it to cellular companies as part of a planned auction. It's been in the works for some time, but the rise of Google Glass and devices like it puts more pressure on the transaction to be completed quickly and cleanly.

To the extent that tethering becomes more widespread, it's hard to predict what the precise consequences of it will be. Will Glass use up more data than the average cell phone? Less? About the same?

Let's consider a typical-use scenario. Take this viral video, which was created when someone wearing Glass caught a beachfront arrest on camera. It's a five-minute clip taken with Glass' standard-issue 720p video equipment. After plugging the YouTube clip into a site that converted it into something downloadable, I learned that depending on the quality settings, the video's filesize ranged from 2.6 MB to as much as 40.6 MB. That's merely how much data it takes to download or stream the video — what you see after everything has been uploaded to YouTube and compressed. The raw video, or what Glass actually transferred to the Internet, was probably even larger.

Google is hoping people will be taking photos and videos with Glass just as frequently as they do now with their smartphones. But experience also tells us that people will inevitably find ways to use their new technology that their creators likely never dreamed of. Here's how Variety's Kevin Kelleher put it:

When Glass debuts, the way we tell stories and watch others tell them may start to change in significant ways. And not just for the people who upload their life moments onto YouTube: Feature films, documentaries, television programming, videogames — many areas could be disrupted, if not by Glass right away, then over time by the technologies that power it.

All that cultural output will require an Internet connection. And it's not just Glass that could take off this way. As Stanford's Rosston said, other products in the wearable-tech category might wind up being the killer tethered device. Or maybe they'll all take over simultaneously, creating a compounded effect on the country's Internet infrastructure.

Isn't Wi-Fi the answer?

With traffic exploding, wireless carriers will have to do everything they can to relieve pressure on their networks. According to one study, 46 percent of mobile data will be shunted off to Wi-Fi by 2017, instead of traveling over 3G or 4G networks. That will be crucial for Glass if it causes the demand for data to spike:


As anyone who's spent time in airports or coffee shops will know, Wi-Fi networks in these public spaces can become pretty congested at peak hours. Telecom expert Roger Entner thinks Glass and other technologies can help mitigate any crowding on Wi-Fi by adopting more sophisticated radios supporting newer Wi-Fi standards (right now, Glass supports a version of Wi-Fi that's been with us since 2003).

Which brings us back to the spectrum auction. One hotly debated subject is how much of the spectrum reclaimed from broadcasters will be sold off to other companies, and how much of it will be reserved for uses like Bluetooth and Wi-Fi — open-access technologies that aren't "owned" by anyone.

How the spectrum auction gets settled will go a long way toward defining the limits of mobile technology. But the same is true vice-versa: How Americans use wireless, wearable tech will have a major effect on how telcos allocate their resources, make strategic acquisitions and create opportunities for other entrepreneurs.

"We don't know if it's Google Glass that's going to be the one to take off, or Apple's iGlass, if you'll excuse the expression," Rosston joked. "But whatever it is . . . they either try to increase capacity or they try and take advantage of [the lack of supply] and raise prices. I think they'll do both."