• by Wendy Davis  @wendyndavis, November 4, 2008

AT&T has joined Comcast in limiting imposing bandwidth caps on subscribers.

This month, the telecom is imposing limits of between 20 and 150 GB per month on a trial basis in Reno, Nev. Consumers' limits depend on which of five service plans they sign up for.

At the low end, those who pay $14.99 a month for speeds of 768 Kbps will be limited to 20 GB a month, or enough bandwidth to download around 10 standard-def movies.

The highest limits are 150 GB a month, for subscribers who sign up for 10 Mbps at $55 a month. The other three plans are: 1.5 Mbps service ($25 a month) with a limit of 40 GBs; a 3 Mbps ($30) with a limit of 60 GBs; and a 6 Mbps ($35) plan with an 80 GB maximum.

After reaching their caps, will be able to purchase additional bandwidth for $1 per GB.

The usage limits are only for new subscribers and existing ones who currently use more than 150 GBs per month. AT&T spokesperson Michael Coe said that less than 1% of users currently consume that much bandwidth.

The company, which estimates that 50% of its bandwidth is used by 5% of customers, told the Federal Communications Commission that the reason it's exploring limits is "to equitably provide affordable broadband services to all of our customers."

"A small minority of our broadband Internet access customers consume a disproportionately large amount of the total bandwidth available to all of the customers on our network," the company said in a recent letter sent to the FCC.

AT&T isn't the only company to test metered usage. Comcast earlier this year announced limits of 250 GB a month. Time Warner also is testing caps--although far lower than what Comcast or AT&T is exploring. The Time Warner caps, now being tested in Beaumont, Tex., start at just 5GBs per month.