DETROIT » Electric car maker Tesla Motors Inc. promises to boost the number of fast-charging stations in the U.S. and Canada to make cross-country travel by electric car possible in the next year.

The company said today that by the end of next month, it will triple the number of charging stations it runs from the current eight, and the number will go to around 100 in the coming year, putting stations within reach of almost the entire populations of both countries.

The pace of construction is about twice as fast as the company had previously announced.

The expanded "supercharger" network will allow owners of Tesla’s $70,000 Model S sedans to travel from Los Angeles to New York, probably by the coming winter, as well as make other long-distance trips. The Model S can travel about 200 miles, or for about three hours, when fully charged. With the network, it can be recharged to 50 percent of its battery capacity in 20 to 30 minutes, allowing drivers to make quick stops before driving on.

The supercharging stations are about 10 times as faster than most public charging stations, Tesla said on its website.

Currently Tesla has eight supercharger stations in California and on the East Coast. It has plans to add four stations in California this summer. Stations also will be added during the summer so drivers can go from Vancouver, British Columbia, to Seattle and Portland; and from Austin, Texas, to Dallas. They also will come on-line quickly in Illinois and Colorado.

In addition, the company intends to add four stations this summer in the densely populated Eastern Seaboard, where it currently has two.

There are no supercharger stations currently planned for Hawaii, according to the company’s website.

Elon Musk, who leads the company, said today that the stations will always be free for owners of the large-battery version of the Model S. Owners of the brand’s smaller-battery version will have to pay for the option of using the stations.

Musk said most of Tesla’s customers don’t know about the supercharger stations, and they won’t have much of an impact on the company’s current sales rate of around 20,000 per year. But they are necessary to appeal to a wider group of more mainstream customers who want to travel between states.

"They want to know that they have that ability to do so, and on a moment’s notice, to go wherever they want," Musk said. "I think it’s really important for accessing a broader audience."

Tesla said by fall, it should have charging stations in most metro areas, with coast-to-coast travel available during the winter along Interstate 80. By 2014, the company expects to have charging stations within reach of 80 percent of people in the U.S. and Canada, and 98 percent by 2015, it said in the statement.

Tesla said new technology is being tested now that will allow its cars to be fully recharged in about 20 minutes. The technology will be available at stations this summer, the company said.