Stock price of California electric car maker down to $25.55 after lock-up period ends and initial investors allowed to sell-off shares

American electric-car maker Tesla Motors has suffered a dramatic dip in its stock price just six months after a successful IPO saw investors such as Toyota and Daimler buy into the California start-up.

Tesla's stock price fell 15 percent on Monday to close at $25.55 at the end of the trading day on the Nasdaq.

The company went public in an IPO last June 28 that was largely seen as successful with Toyota and Daimler each buying about $50 million in shares. Just last month, battery-maker Panasonic bought $30 million in Tesla stock.

Much of the drop in the price this week can be attributed to the end of the lock-up period for the first investors. Investors who bought stock during the IPO are only now allowed to sell-off shares.

Carter Driscoll, an analyst with Capstone Investments which has deemed Tesla stock a "sell", says that his firm has come up with a long-term share price estimate of $22.

"A lot needs to go right to justify the current valuation. They have never mass-produced cars. They start paying back government loans in 2012."

Tesla has borrowed $465 million from the U.S. Department of Energy to produce the Model S at the newly acquired former NUMMI plant in California. The model is due for a debut in 2012.

Gallery: Tesla stock price down 15 percent