Electric car maker Tesla has managed to sell enough cars to send its stock soaring this year -- it's up 300 percent so far -- but it has achieved that success without traditional TV advertising -- indeed virtually without advertising of any sort, Advertising Age observed on Monday. By contrast Nissan spent $25 million to advertise its own electronic vehicle, Leaf in 2012, the trade publication noted, citing a study by Kantar Media. Tesla is relying primarily on the Internet to spread the word about its all-electric vehicles, which are being sold in stores rather than conventional dealerships. Right now, the stores are our advertising, Tesla spokeswoman Alexis Georgeson told AdAge. We're very confident we can sell 20,000-plus cars a year -- without paid advertising. Tesla cars do turn up on television these days, but mostly during news accounts about them. They're selling very few cars when you think about it -- but they are getting an awful lot of buzz, said Jeremy Anwyl, vice chairman of auto consultancy Edmunds.com.