Comcast is considering imposing monthly usage limits for all of its Internet customers.

David Cohen, executive vice president of America's largest cable company, predicted at a conference Wednesday that in five years' time, the company will have "a usage-based billing model rolled out across its footprint."

That means Comcast (CMCSA) customers could only consume a certain amount of data before facing extra charges for going over their limits.

Cohen said the company would aim to set the limit at a level where "the vast majority of our customers" wouldn't be affected. He speculated that the limit might be set at 350 gigabytes or 500 gigabytes per month. A cap of that size would allow you to download or stream between 70 and 125 HD movies, which typically run about four or five gigabytes in size.

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Cohen said he doesn't think Comcast will ever have a system in which "80% of customers" are impacted by data limits and are forced to pay for additional usage, though he added that it's "very difficult to make predictions."

"I don't think that's the model that we are heading toward, but five years ago, I don't know that I would have heard of something called an iPad," he said.

Comcast is currently experimenting with 300 GB data limits in some markets, charging those customers $10 for each additional block of 50 GB. There's also a 5 GB "flexible data" option for light users. Those plans were introduced after the company scrapped its hard 250 GB monthly cap back in 2012.

The move could also affect current Time Warner Cable (TWC) customers should the companies' pending merger be approved by regulators. If the deal is approved, the combined group will be the country's dominant provider of television channels and Internet connections, reaching roughly one in three American homes.