The acquisition of Zipcar for nearly $500 million will bring a financial windfall for local business mogul Steve Case, who holds a 20 percent stake in the car sharing company.

Zipcar announced Wednesday morning it had accepted a buyout offer worth $12.25 per share from rental car company Avis. The price represents a 49 percent premium over Zipcar’s closing price on Dec. 31.

The deal is expected to close in the spring of this year, pending shareholder and regulatory approval.

Case’s most recent regulatory filing for Zipcar, dated Aug. 28, tallies his ownership at 7,852,905 shares, or 19.6 percent of all shares. At the $12.25 per share price, his cut comes to $96.2 million.

Zipcar counts 760,000 members who log onto the service’s Web site or mobile app to rent an automobile at an hourly rate. The company has cars in 20 metropolitan areas across the United States, Canada and Europe, as well as more than 300 college campuses.

Case was among the earliest backers of car sharing. Revolution initially purchased Flexcar, a competing service, in 2005 and merged the company with Zipcar two years later.

Case is the chief executive and chairman of Revolution, a District-based investment firm. He invests personal money through the firm, as well as money raised from limited partners.

Case declined to comment on the sale through a spokeswoman.

Follow Steven Overly on Twitter: @StevenOverly