Two law firms say they are investigating whether shareholders could have gotten a better deal in the $4.3 billion sale of the utility company.

The New York-based Rosen Law firm and the San Diego-based Johson & Weaver, LLP announced separate investigations of the Hawaiian Electric Industries board for possible breaches of fiduciary duty and other alleged violations of securities law, by failing to adequately shop Hawaiian Electric Industries to maximize shareholder value, before agreeing to be acquired by NextEra Energy Inc.

However, some analysts believe NextEra paid too much for Hawaiian Electric.

NextEra “may have materially overpaid” for Hawaiian Electric, in part because it’s assuming a tax liability as part of the spin off, Sanford C. Bernstein analysts led by Hugh Wynne said Thursday in a note to clients.

Holders of Hawaiian Electric will receive 0.2413 shares in NextEra plus a 50-cent one-time dividend for each share they own, the companies said Wednesday in a joint statement. As part of the deal, Hawaiian Electric will also spin off the parent of American Savings Bank.

Including an estimated $8 a share from the bank spin off, the deal values Hawaiian Electric at about $33.50, the companies said during an investor presentation. Without the spin off, the cash and stock amounts to $25.69 a share, or $2.63 billion, based on yesterday’s closing prices.

Including debt, the total value of the transaction is about $4.3 billion.

NextEra sees Hawaiian Electric Industries Inc., which serves 95 percent of the state, as a testing ground for the coming transition from fossil fuels to power generated from the sun and wind. Hawaiian Electric is among utility owners most vulnerable to challenges by solar power as more customers generate electricity from rooftop systems.

“You can think about Hawaii as a postcard from the future of what’s going to happen in the electric industry in the United States,” James Robo, chairman and chief executive officer of Juno Beach, Florida-based NextEra, said by phone interview Wednesday. “As renewable generation gets cheaper, as electric storage becomes more efficient and possible, all electric utilities are going to have to face this.”

Solar electricity, helped by federal and state tax incentives, is already as cheap as utility-supplied power in 10 states including Hawaii, Deutsche Bank AG said in a report published in October.

NextEra can add more renewables and transition to cleaner fuels while lowering customer bills in Hawaii, Robo said. Hawaii relies on imported oil for its generators.

NextEra, the nation’s largest buyer of natural gas, can also help Hawaii import cleaner burning liquefied natural gas to generate power, said Hawaiian Electric Chairman and CEO Constance Lau in a conference call with investors.

The deal requires approval from state and federal regulators and shareholders. It’s expected to be completed within about 12 months. NextEra won’t fire any workers at Hawaiian Electric for at least two years after the close, the companies said.

Hawaiian Electric was incorporated in 1891 from a royal charter by King David Kalakaua, before Hawaii became part of the U.S., according to the company’s website.