Expert witnesses representing NextEra Energy Inc. and Hawaiian Electric Industries Inc. said Tuesday a systemwide upgrade to smart meters would cost the utility’s consumers up to $350 million.

The smart meters were a main topic during the sixth hearing put on by the Public Utilities Commission to review NextEra’s proposed $4.3 billion purchase of Hawaii’s largest utility.

Bryan Olnick, vice president of distribution operations at Florida Power &Light, and Colton Ching, vice president of Energy Delivery at Hawaiian Electric Co., testified as the third and fourth of 12 expert witness representing NextEra and HEI at the hearings. There are 39 witnesses total from Next­Era, HEI, government agencies, energy companies and environmental groups who will be available for questions during the hearings.

Tuesday was the sixth day of 12 scheduled hearings at the Neal S. Blaisdell Center conference room where the PUC and other interested groups can question NextEra and HEI officials about the sale. The companies need approval from the commission for the sale to close. NextEra Energy Hawaii President Eric Gleason and Hawaiian Electric CEO Alan Oshima testified earlier.

A majority of the hearing was centered around smart-meter deployment, as Olnick is an expert and the primary person in charge of smart-meter deployment at NextEra’s Florida electrical utility, Florida Power &Light.

Smart meters are one aspect of upgrading HECO’s grid that the utility says will increase the reliability of its service. Smart meters combined with a modernized grid would allow the utility to detect where and when there are potential power outages. They also allow customers to access energy usage data in near real time versus waiting the full billing cycle.

“The costs would be recovered over time by the customers that we serve,” Ching said.

Utility investments in the grid, upon approval from the PUC, are paid for in base rates. The cost savings and potential opt-out possibilities for customers are not known until HECO submits its smart meter application with the PUC.

Olnick said NextEra’s experience deploying nearly 4.8 million smart meters at its Florida Power &Light utility will help accelerate the process in Hawaii.

“(With) what we have done at FPL, we have a good sense of some of the value we can offer,” Olnick said.

Ching said NextEra could install smart meters systemwide for 4 percent less than HECO.

“We are putting together the final aspects of the application,” Ching said. “That work is estimated to be between $300 and $350 million under an un-merged scenario but would be 4 percent less in a merged scenario.”

Tuesday marked the halfway point of the original timeline for the hearings, but PUC Chairman Randy Iwase said the 12 hearings aren’t enough. Iwase said he expects the hearings to go into January and possibly February.

Iwase said the PUC is reviewing whether some confidential documents would be made public. The hearings were closed to the public twice over the last six days. Oshima answered questions for 45 minutes behind doors Dec. 4, and Gleason for about 35 minutes Monday.

NextEra filed 60,000 pages of documents in defense of its proposed purchase, and about 5 percent, or 3,000 pages, of those were marked confidential.

Tom Gorak, chief counsel for the PUC, asked Ching what NextEra brings to the table that Hawaii doesn’t in terms of getting the state to its 100 percent renewable goal.

“They have expertise there where we don’t,” Ching said.

Ching said NextEra is involved with the refreshing of HECO’s renewable-energy plans — the PUC has sent HECO back to the drawing board twice for its renewable-energy plans. NextEra Energy teams have been assisting HECO with the smart-grid program, Ching said.

According to the current schedule, the hearings will continue today through Friday and Monday, Tuesday and Dec. 16.