Residents of the three biggest Bay Area cities will soon be able to supercharge their Internet service.

AT&T announced Monday that it will begin offering its super-high speed GigaPower broadband service in San Francisco, Oakland and San Jose beginning next year. The service offers speeds of up to a gigabit per second. That’s about 20 times speedier than the fastest residential Internet service AT&T currently offers and about four times faster than the speediest service available through Comcast, which is the Bay Area’s dominant broadband provider.

“Our customers are asking for faster speeds, and we’re building out faster speeds for them,” said Marc Blakeman, vice president of external affairs for AT&T’s California operations.

AT&T plans to start in certain neighborhoods in those three cities as soon as January and build out its service from there, Blakeman said. He declined to say which neighborhoods AT&T would offer GigaPower in first.

The company already offers its ultra-speedy Internet service in parts of Cupertino and has announced that it will offer it soon in Mountain View as well. AT&T won’t expand to other Bay Area communities until after it has launched service in the big three cities, Blakeman said.

However, not everyone in those cities can expect to see service. AT&T has no plans to offer ubiquitous access to GigaPower in any of the communities it serves, Blakeman said. That could be bad news for residents who live in outlying areas, who already have trouble getting standard broadband service.

Residents who do get access to the service can expect to pay handsomely for it. Blakeman declined to say what the prices will be, but AT&T charges $110 a month for stand-alone gigabit Internet service in Cupertino. By contrast, consumers can get relatively speedy 75-megabit-per-second service from Comcast on a promotional rate of $45 a month.

Once the dominant provider of Internet access, AT&T has faced growing competition. Comcast has been steadily upping its speeds and now offers service as fast as 250-megabits per second, albeit for a pricey $150 a month. The cable provider offers its own gigabit Internet service to certain customers in the Bay Area. That service currently requires professional-grade equipment, but the company plans to offer it to consumers with standard equipment next year.

Meanwhile, Google has announced plans to bring its own gigabit Internet service — Google Fiber — to San Jose and has already applied for permits to build boxes to house its networking equipment.

AT&T’s rollout of GigaPower in the Bay Area is part of a broader expansion nationwide. In its announcement Monday, the company said it would bring the service to 38 new communities around the nation, including those in the Bay Area. Among the other new markets will be Fresno, Bakersfield and San Diego. The company also announced that it has already started to offer the service in parts of Los Angeles.

Thanks in large part to the popularity of streaming video services such as Netflix, consumers are using more bandwidth, noted Jeff Kagan, an independent telecommunications analyst. It’s not clear that there’s a widespread need for 1-gigabit speeds, but the big telecommunications companies are building out that capacity with the expectation that consumers eventually will demand it, he said.

“The major (telecommunications) players recognize that everything is going be coming over the Internet, and they need to have the capacity for it,” Kagan said.

Contact Troy Wolverton at 408-840-4285. Follow him at Twitter.com/troywolv.