Hawaiian Electric Industries stock rose sharply today then gave back much of its gains following the disclosure that a start-up company was preparing a takeover offer with the intention to take the company private.

The stock price, which opened today at $23.87 a share, jumped to more than $26 before quickly settling back to close at $24.76, up 3.7 percent for the day.

The price spike came after reports that a company called Kuokoa Inc. was preparing a bid to acquire HEI and take the company private.

Roald Marth, chief executive of Kuokoa Inc., said yesterday that if the acquisition was successful, the company would then write off HEI’s fossil-fuel burning assets and invest billions to convert the power-generating system to entirely renewable energy within 10 years.

He said he had reached out to HEI to start discussions but the company had not responded yet. An HEI spokesman declined comment.

Marth, a motivation speaker and venture capitalist, has hired Ted Peck, the state energy administrator, to be Kuokoa’s president. Peck’s last day with the state is today.

Marth is CEO and Richard Ha of Hamakua Springs Country Farms on the Big Island is chairman.

While Marth lauded the people operating HEI, describing it as a well-run utility, he said the company is not moving fast enough toward its clean energy goals because of the difficulty as a publicly traded company in investing the billions needed to make the conversion.

Marth told the Star-Advertiser that his group would offer an undisclosed premium over the company stock price. Based on today’s opening stock price, the company has a market value of about $2.3 billion.

Marth acknowledged that he doesn’t have the money to pull off the deal but would have to persuade investors to back the venture.

Kuokoa’s plan would entail taking the company private, selling its American Savings Bank subsidiary and over 10 years converting the entire power system to renewable energy. Marth estimated the 10-year plan, which would include establishing a statewide electricity price at 20 cents per kilowatt hour and building wi-fi technology into the smart grid, would cost $35 billion.

Kuokoa’s plan has been greeted with skepticism by some people approached as would-be investors.

"This is just a comedy," said Enterprise Honolulu President Pono Shim, who noted that Marth asked him to invest $20,000 to become a founding director in Kuokoa.

HEI is parent to Hawaiian Electric Co. on Oahu, Hawaii Electric Light Co. on the Big Island, Maui Electric Co. and American Savings.