Much of the information provided by NextEra Energy Inc. in arguing for approval of its proposed $4.3 billion purchase of Hawaiian Electric Industries Inc. has been marked confidential and might never be discussed in public.

Public Utilities Commission Chairman Randy Iwase closed the hearings to the public for 45 minutes Tuesday and said Thursday he has three requests from participants to temporarily close the hearings again.

It was the fourth day of the scheduled 12 days of hearings in which NextEra and HEI executives are responding to questions from state and county officials, environmental groups and others. NextEra Energy Hawaii President and CEO Eric Gleason answered questions Thursday, noting it was the first anniversary of the announcement that his company intended to buy HEI. The PUC must approve the purchase for it to happen.

NextEra has filed 60,000 pages of documents in defense of its proposed purchase, but thousands of those pages are marked confidential, said Terrance Revere, an attorney for the state Office of Planning. Henry Curtis, executive director of Life of the Land, said about half of the pages filed are stamped confidential.

Confidential documents cannot be discussed during the hearings unless the discussions are held behind closed doors.

The issue came up Thursday when one participant questioned how much money NextEra expects to save by reducing operating costs.

NextEra has promised to cut electrical rates by $60 million over the first four years of its ownership of the Hawaii utility. The company expects to meet that goal through reductions in operations and maintenance costs. But what NextEra hasn’t said is how much more than $60 million it expects to save through lower costs.

A document with that number is marked confidential, said Jason Kuzma, a Seattle attorney representing the Pam and Pierre Omidyar-funded Ulupono Initiative.

Gleason said the company has determined what it expects to save in operations and maintenance costs, but he didn’t disclose it. Instead he focused on the benefits to customers.

“The first thing customers are going to get is rate credits that total $60 million over the first four years,” Gleason said. “We expect to be able to reduce operating cost over time, and as part of the overall package that we proposed, we put our money where our mouth is and we put $60 million on the table for customers in assured rate benefits.”

Iwase said he is not happy about having to hold closed-door session and asked all participants to send him their lists of questions they want to ask pertaining to confidential documents by the end of business today. He wants the participants to explain why the documents should remain confidential and why they are relevant to the PUC decision.

Iwase can make the documents public if he decides there is no valid reason to keep them secret.

“There are reasons to have documents listed as confidential,” Iwase said. “There are business interests that have to be protected, trade secrets that have to be protected, financial secrets that might have to be protected and should not be disclosed in the context of this hearing in an open session. You’ve got to balance it.”

The hearings, being held at the Neal S. Blaisdell Center, will continue Monday through Dec. 11 and Dec. 14-16.