Officials have increased their estimates for how much it will cost to operate Oahu’s rail transit system once it’s up and running.

Previously, in a 2012 report, they had projected an annual cost of $116.7 million to operate the rail line in 2021, about a year after the rail system fully opens.

Now, documents provided to the state’s finance director revise that figure upward. In a draft report, the Honolulu Authority for Rapid Transportation anticipates it will cost $130 million to run rail in 2021.

Anticipated higher electricity costs — and more consumption of that energy by the rail system — are partially to blame for the estimated $13 million increase for 2021, HART officials say. Inflationary costs are steeper than what had been estimated for the project’s 2012 financial plan, they add.

HART leaders emphasize that the latest revisions are preliminary figures, and that they released them in draft form to help state lawmakers weigh whether to extend Oahu’s rail tax during their most recent legislative session.

"We’re constantly checking numbers and trying to revise them," HART Executive Director Dan Grabauskas said recently. "We were asked to give the most current information we have even though it isn’t final. Some of this stuff is still just a work in progress."

HART is expected to release later this year a new financial plan for the project, including its official updated cost estimates.

The Legislature did eventually pass a five-year extension of the rail tax. The measure looks to raise an additional $1.8 billion to finish construction of the 20-mile system, and would explicitly prohibit using those dollars for future system operations.

It’s not clear yet whether Gov. David Ige will sign the five-year tax extension into law.

Meanwhile, as the cost estimates increase, it remains unclear exactly how those rail operations and maintenance costs will be covered. Transit leaders have said it could be another two years or so before a detailed plan emerges.

They’ve said that they need to set the rail system’s fares first, and then they’ll know how many dollars will be needed on top of that to cover the full operational costs.

The updated operations cost figures, provided to Ige administration Finance Director Wes Machida, estimate that the system will take in $35 million in revenue in 2021, leaving the city to cover the additional $95 million or so in operations costs for that year.