Tesla said Friday it increased the size of the stock and bond offering that electric car maker announced a day before and that CEO Elon Musk intends to buy even more equity.

The company is selling 3.1 million shares at a price of $243 per share through underwriters Goldman Sachs and Citigroup, according to filing. That's up from the 2.7 million shares previously expected to be sold at the offering. The company also said it was boosting its convertible notes offering to $1.6 billion, according to filings.

Musk now intends to purchase up to 102,880 shares in stock worth $25 million, more than double his previous indication to buy 41,896 shares. The updated figures bring the total value of the offering to about $2.7 billion, up from the $2.3 billion expected following the Thursday announcement.

"As for the upsize of the deal - it's usually driven by greater demand. When they shop around the deal and it ends up being larger, it's usually because there's significant demand," Nomura Instinet analyst Christopher Eberle told CNBC in an email.

"As for why now? I think a better question is 'why not now?' It was pretty well telegraphed after the autonomous driving day that they were going to do a cap raise," Eberle added. "Rather than let the rumors dictate the movement of the stock, it's better to just stop delaying the inevitable and get it done. This buys them some breathing room for the next several quarters in the case of a weaker demand environment."

Wall Street's positive reception on Thursday to Tesla's plans to raise additional capital may have encouraged the underwriters to augment the size of the offering. Tesla shares rose 4% Friday following a 4.3% pop on Thursday and was last seen trading at $255.40.