The state consumer advocate said Monday that Florida-based NextEra Energy Inc.’s proposed $4.3 billion purchase of Hawaii’s largest electric utility is not in the public interest.

Consumer Advocate Jeffrey Ono said NextEra has not clearly laid out how its purchase of Hawaiian Electric Industries will result in significant benefits for consumers.

The agency said NextEra offered “flawed and broad speculative savings estimates” during the review.

“These kinds of asserted savings based on NextEra’s faulty calculations effectively overstate the potential benefits of the proposed merger, thereby creating an illusory benefit,” Ono said. “Since our mission is to protect and advance the interests of Hawaii’s consumers, we have serious concerns about this proposed merger.”

NextEra, which said in December it plans to buy HEI, promised HEI customers would save approximately $60 million over four years if the sale is approved.

“The company’s filings do not clearly or consistently explain how these savings will materialize to the full extent they have been claimed,” the consumer advocate said in a press release. “This includes, for example, millions of dollars in purported savings resulting from broad reductions in operations and maintenance expenses that have not been clearly laid out despite the company having ample opportunity to clarify these and other benefits during the discovery period.”

The consumer advocate filed 548 pages of testimony with the Public Utilities Commission on Monday, recommending several conditions to the NextEra deal that need to be adopted to protect consumers and to immediately return merger savings to consumers. The PUC must approve the purchase before it can go forward. The PUC has said it will make a decision by June.

The consumer advocate’s opposition to the sale followed Gov. David Ige’s statement July 20 that he is against the sale as it is currently structured.

NextEra and HEI must provide an updated economic impact analysis for at least five years following the transaction that includes planned changes in employment at the utilities, the consumer advocate said. NextEra must also provide planned changes of spending on services and supplies located in Hawaii as well as planned changes in customer bills.

“Without such an analysis, the economic impacts of the merger are undetermined and the joint applicants have not met their burden of proof to demonstrate that the proposed transaction will positively affect Hawaii’s economy,” the consumer advocate said.

The state office said the lack of rooftop solar at NextEra’s Florida subsidiary raises questions about whether the sale would adversely affect competition in Hawaii.

“Given the lack of distributed generation in Florida, there are unanswered questions,” the consumer advocate said.

There are about 3,000 customers with rooftop solar at NextEra’s Florida utility, Florida Power & Light, among the subsidiary’s 4.8 million customers. Hawaiian Electric — which includes Hawaiian Electric Co. on Oahu, Hawaii Electric Light Co. on Hawaii island and Maui Electric Light — has only 450,000 customers but has approved almost 70,000 rooftop solar systems.

Alan Oshima, president and CEO at HECO, said the consumer advocate’s testimony will be considered as the companies move forward with the review process.

“Given the importance of this merger to Hawaii’s future, we appreciate that there are multiple perspectives. We will carefully review the consumer advocate’s testimony and recommendations,” Oshima said. “We believe NextEra Energy — with its extensive renewable energy expertise and resources — will strengthen and accelerate Hawaiian Electric’s clean energy transformation. And together, we will work toward achieving Hawaii’s goal of 100 percent electricity from renewable energy by 2045. As more information is provided throughout this process, we strongly believe that others will also conclude that this partnership with NextEra Energy is in the best interests of our customers and Hawaii’s future.”

The consumer advocate is the third state agency that has said the answers provided by NextEra and HEI in the review process were insufficient.

“Applicants, instead of utilizing this proceeding as an opportunity to establish a good first impression, fall short and appear to rely on a ‘trust us — the benefits will be there’ approach,” the consumer advocate said.

In their testimony, the state Office of Planning and the Department of Business, Economic Development and Tourism recommended the PUC reject the sale, with no responsibility to give the applicants a second chance.

The two state agencies were among the 28 approved “intervenors” in the case that filed testimony about the acquisition with the PUC in July. None of the groups filed testimony with full support of the sale. Most of the groups said they either opposed the purchase or could accept it only with conditions.

As part of the PUC’s review, NextEra and HEI must respond to informational requests and questions posed by the approved groups.

NextEra’s and HEI’s rebuttal to the consumer advocate and other testimony in the case is scheduled to be filed Aug. 31.