Beating Comcast Corp., little RCN Corp. is launching 1 gigabit internet speeds for residential customers in the Philadelphia market.

The cable overbuilder will announce the gigabit speeds, packaged at $69.99 a month with a $15 modem rental, on Thursday and advertise the service later this week or next week. The price is guaranteed for a year.

The service will be the fastest internet speed over regular cable wires in the Philadelphia suburbs, RCN says.

Chris Fenger, RCN's chief operating officer, said Tuesday that data consumption over the internet has been growing at a "dramatic rate," 35 percent to 50 percent a year. Subscribers "need the bandwidth, and we want to make sure we are ahead of that curve," he added.

RCN subscribers streaming more data over Netflix and Amazon and also connecting more data-hungry devices such as smartphones and tablets to the internet, Fenger said. RCN, one of the nation's few so-called cable overbuilders that competes with incumbent local cable operators such as Comcast, serves the Delaware County towns of Clifton Heights, Upper Darby, Drexel Hill, and Yeadon, in addition to municipalities in the Allentown area. Fenger said that RCN has launched gigabit speeds in Chicago and Washington, too.

RCN's launch comes as Comcast recently boosted internet speeds in the northeastern United States, and as Google Fiber has indicated it would retreat from its gigabit project.

Comcast has a gigabit service, branded as Gigabit Pro, that requires special wiring to homes. Comcast also offers gigabit speeds to its subscribers over its traditional cable lines, similar to RCN's offering, in Detroit, Chicago, Atlanta, and Nashville. Comcast also expects to offer it in Miami but has not said when it would bring the service to Philadelphia.

Comcast has priced its gigabit internet product at $140 a month with an additional $10-a-month modem rental. It's also test-marketing a price point at $70 a month with a three-year contract, spokesman Charles Douglas said Wednesday.