Charter cable Internet customers who don't subscribe to Charter's TV service are using an average of more than 400GB of data a month, the company said yesterday.

While Charter doesn't impose data caps on its Spectrum Internet service, the newly released stat helps illustrate how ditching cable TV and relying on streaming services can push customers closer to incurring data overage fees. Comcast and other ISPs impose monthly caps of 1TB.

"The demand for both speed and throughput on our network continues to increase," Charter CEO Tom Rutledge told investors in an earnings call yesterday. "Monthly data usage by our residential Internet customers is rising rapidly and monthly median data usage is over 200GB per customer. When you look at average monthly usage for customers that don't subscribe to our traditional video product, usage climbs to over 400GB per month, which compares to an average mobile usage of well under 10GB a month." (Charter also offers mobile service through a reseller agreement with Verizon.)

The 200GB figure for all Charter Internet customers and 400GB figure for broadband-only customers aren't directly comparable because Rutledge provided a median in the first case and an average in the second. This appears to be by design—we contacted Charter public relations, and the company declined to provide any further statistics. "The language used was accurate," Charter said. "The residential Internet customer monthly data usage (all subscribers) stat was a median and the stat on monthly usage of customers who don't subscribe to our traditional video product was a mean average. Those are the only stats we are providing today on data usage."

Still, the average data usage for broadband-only customers may be significantly higher than the average for all customers. Recent OpenVault research on the US cable industry found that Internet customers are using an average of 268.7GB per month and a median of 145.2GB. OpenVault, which sells equipment that helps cable companies track data usage, also found that 4.1 percent of households use at least 1TB a month, up from 2.1 percent the previous year.

Comcast median usage more than 200GB

Last week, Comcast said its median broadband home uses more than 200GB a month, up 34 percent year over year. Comcast didn't say how much data its broadband-only customers use.

Comcast charges $10 fees for each additional block of 50GB or $50 monthly for an upgrade to unlimited data. (In some areas, Comcast provides unlimited data for "free" if you rent its $15-per-month xFi Advanced Gateway.)

While Charter doesn't impose data caps today, it could do so a few years down the road. Charter is prohibited from selling plans with data caps and overage thanks to a merger condition imposed on its 2016 purchase of Time Warner Cable, but that merger condition expires in 2023.

Rutledge also said yesterday that more than 80 percent of Charter customers subscribe to speeds of at least 100Mbps, and 30 percent subscribe to plans providing at least 200Mbps. Charter, the second biggest US cable company after Comcast, offers gigabit service throughout its 41-state territory.

Charter has 24 million residential Internet customers, with about half the households in Charter territory subscribing to Charter broadband. Research last year found that Charter is the only high-speed broadband choice for 38 million Americans (in terms of total people, not just households).

Disclosure: The Advance/Newhouse Partnership, which owns 13 percent of Charter, is part of Advance Publications. Advance Publications owns Condé Nast, which owns Ars Technica.