Tesla shares continue to scream to the upside, with the hot-as-hell stock adding another 15 percent on Tuesday and Wednesday alone. And a massive options bet suggests that the party isn't over yet.
In Wednesday's biggest trade, one trader bought 1,633 January 2015 320-strike calls at $27.05 a share. Since each options contract controls 100 shares, these 1,633 contracts cost a total of $4.4 million in premium.
(Read more: Tesla soars, Ford falls in 'Consumer Reports' study)
What's incredible about this trade is just how much Tesla will have to rise for it to be profitable. A call option merely grants its buyer the right to buy shares of a stock at the given strike price at expiration, so if Tesla is trading below $320 in January, the entire $4.4 million position will become worthless.
And for the trade to make a profit, Tesla needs to rise even higher to make up for the premium spent. That's why the break-even price on this trade is $347.05—nearly $100, or 40 percent, above where the stock is trading Wednesday (though it's worth keeping in mind that if Tesla shares rise quickly, the options position could likely be sold ahead of expiration for a profit).
"That's pretty crazy," said options trader Brian Stutland of the Stutland Volatility Group. "It's rare that you see a 30 percent out-of-the-money call a year out unless you really think the stock is going significantly higher soon."
(Read more: Tesla forecasts a big 2014)
Though it's unclear whether the trader was buying the options to open a new position or to close out an old one, "either way, you're outlaying a ton of cash," Stutland said. "We haven't seen the top in Tesla—that's the bottom line in that trade."
Tesla shares recently got a boost from its plans to build a massive new battery factory. In turn, that news encouraged Morgan Stanley to double its price target on the stock, to $320, in a Tuesday note. More good news Tuesday came when Consumer Reports named Tesla's Model S the highest-rated model in its annual auto issue.
—By CNBC's Alex Rosenberg. Follow him on Twitter: @CNBCAlex.
Follow the show on Twitter: @CNBCOptions.
