Billionaire buy-and-hold investor Ron Baron said Wednesday he's betting on explosive growth for Tesla in the next decade—calling the stock a "huge opportunity." "I love Tesla," he told CNBC's "Squawk Box" in an interview. "I think we're going to make between 10 and 20 times our money in the next 10 years." Read MoreBillionaire Ron Baron: THIS is keeping lid on stocks Baron started buying Tesla about three years ago, when the stock was about $33 a share. Over time as it fluctuated, he accumulated 1.2 million shares for a total cost of $261 million. Based on Monday's close of $250 a share, his stake in Tesla was worth $302 million.

Initial purchase date 5/10/2012 Initial purchase price $33.11 Unit cost per share over time $218.43 Total cost to buy 1.3M shares $282,714,299 Current market value of stake $299,804,963 Source: Baron Capital 11/04/15

The current market value of Tesla is more than $30 billion. In four or five years, Baron said the stock could be worth $120 billion. "In 10 years, you have another triple behind that." The electric automaker expects to sell about 55,000 units this year, with deliveries for the new Model X sport utility vehicle slated to start in the third quarter. The company hopes to sell 500,000 vehicles annually by 2020. "I think they'll do it a little bit faster," the Baron Capital chairman and CEO predicted. "In 2020, they're doing $35 billion or $40 billion [in revenue], making $6 billion or $7 billion in profit." Stocks like Tesla and Under Armour fall into a smaller part of Baron's portfolio that he terms "open-ended opportunity investments." Israel-based Mobileye, a developer of technologies for camera-based advanced driver assistance systems, is another example, he said. "These companies are in a different league. They have dimension, extra elements." "Safe investments make up 60 percent to 80 percent of my portfolio," Baron continued. "Manchester United is a safe investment. They are a competitive advantage business, where there are significant growth opportunities and they can double in five or six years."

Baron Stake in Manchester United (MANU) Initial purchase date 11/15/2012 Initial purchase price $12.74 Unit cost per share over time $15.69 Total cost to buy 16.1M shares $253,611,857 Current market value stake $263,939,405 Source: Baron Capital 6/15/15