Tesla plans to double the number of Supercharger locations in North America by the end of 2017, the company said in an investor letter on Wednesday.Tesla currently has 373 Supercharger stations in North America and began its expansion in January.

The company has 805 Supercharger stations worldwide with a total of 5,159 chargers, according to the company's website.Tesla said the move is part of its effort to rapidly expand its Supercharger network.

The Supercharger is Tesla's fast-charging station that used to be free for owners, but now costs a small fee for new customers.Tesla's Supercharger network provides high-speed charging that restores 170 miles of range in 30 minutes.

That's extraordinarily fast for electric vehicle charging and is a key aspect of the Tesla customer experience.For comparison, Business Insider's Matt DeBord found a wall socket charged a Model S at the glacial pace of one mile per hour.

A non-Supercharger, Tesla partner charging station juiced the car back to 30 miles in one hour.Tesla said it has invested hundreds of millions in the Supercharger network, mostly in the US.

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