Cox is continuing the trend of bringing data caps and overage fees to customers in new cities.

Cox, the third largest cable company in the US after Comcast and Charter, has 6 million residential and business customers in 18 states. Much like Comcast, it has instituted a 1TB (1,024GB) monthly data cap and charges $10 for each additional 50GB block of data. Also like Comcast, Cox has been bringing the overage fees to a few cities at a time instead of deploying them to its entire territory all at once.

Cox brought the data caps first to Cleveland, Ohio, and then to Florida and Georgia in October 2016. This week, Cox expanded the overage fees to Arkansas; Connecticut; Kansas; Omaha, Nebraska; Iowa; and Sun Valley, Idaho. Customers can get data usage alerts from a browser, e-mail, text message, or automated phone call when they hit 85 percent, 100 percent, and 125 percent of their monthly data plans.

Cox hired NetForecast to test the accuracy of its meter. This is the same vendor used by Comcast, but the Comcast meter has suffered from occasional mistakes, and plenty of customers suspect the meter is wrong (even if they can't prove it).

The 1TB caps apply for download speeds from 5Mbps to 300Mbps, and Cox customers can view their measured data use on the Cox website or in an app. In some areas, Cox offers a "Gigablast" fiber service with gigabit upload and download speeds. Technically, there is a 2TB cap for the gigabit fiber customers. However, the company's website says that "Gigablast usage does not currently display in the Data Usage Meter." Fiber customers won't be charged overage fees just yet.

"Our meter does not currently track the data usage of Gigablast customers, therefore we do not currently charge Gigablast customers who exceed usage allowances in the markets where we have implemented use-based billing," a Cox spokesperson told Ars.

There are more states where Cox hasn't yet started charging overage fees, such as Arizona, California, Louisiana, Nevada, Oklahoma, Rhode Island, and Virginia. It seems likely that Cox will keep expanding the caps, but it's not saying when it will do so.

"We have no additional locations to announce today," Cox told Ars. "As decisions are made about any subsequent locations, we will announce these plans to our customers well in advance."

In newly capped areas, Cox customers will initially be allowed to exceed the caps for two months without being charged. The grace period is to help customers "get accustomed to this change," Cox says. However, there will be no grace period for customers who exceed caps beginning with bills dated May 22, 2017, the company says.

By contrast, Comcast offers two courtesy months with no overage charges for the first year, and it limits overage charges to $200 a month. Comcast customers can also get more than two courtesy months if they are judicious in their use: "If you use more than a terabyte two times or less in a 12-month period, your courtesy month balance will reset to two at the end of these 12 months," Comcast says. "However, if you use more than a terabyte three times in a 12-month period, no more courtesy months will be given."

Cox defended the caps by saying that only 1 percent of customers use at least 1TB a month. With 1TB, a customer can "Watch 140 two-hour HD movies, watch 300 half-hour standard definition TV shows, watch 1,500 three-minute videos, surf the web for 3,000 hours, [and] listen to 30,000 songs that are 4-minutes long each," the company says.